2011 Vol. 29, No. 3
Display Method:
2011, 29(3): 417-426.
Abstract:
This paper summarizes the history of seismic sedimentology, with a brief discussion of its definition, geologic and geophysical background, key techniques, and future developments. Seismic sedimentology is a new geoscience discipline that has been gaining support from industry and academia both in western countries and in China. Seismic sedimentology is closely related to seismic stratigraphy and sequence stratigraphy, with an emphasis on study of sedimentary rocks and depositional processes. Under current technology, seismic sedimentology is an integration of seismic lithology and seismic geomorphology. The procedure is benefited from a technical breakthrough that images seismicallythin beds by phantom mapping within a timeequivalent seismic stratigraphic framework, which makes a better use of seismic horizontal resolution power. Ninetydegree phasing and stratal slicing are two key, practice and economic techniques. In China, new developments of seismic sedimentology in near future may occur in seismic lithologic methods, seismic depositional models, and study guidelines that are tailored for different types of nonmarine basins.
This paper summarizes the history of seismic sedimentology, with a brief discussion of its definition, geologic and geophysical background, key techniques, and future developments. Seismic sedimentology is a new geoscience discipline that has been gaining support from industry and academia both in western countries and in China. Seismic sedimentology is closely related to seismic stratigraphy and sequence stratigraphy, with an emphasis on study of sedimentary rocks and depositional processes. Under current technology, seismic sedimentology is an integration of seismic lithology and seismic geomorphology. The procedure is benefited from a technical breakthrough that images seismicallythin beds by phantom mapping within a timeequivalent seismic stratigraphic framework, which makes a better use of seismic horizontal resolution power. Ninetydegree phasing and stratal slicing are two key, practice and economic techniques. In China, new developments of seismic sedimentology in near future may occur in seismic lithologic methods, seismic depositional models, and study guidelines that are tailored for different types of nonmarine basins.
2011, 29(3): 427-439.
Abstract:
Many geologists have paid attention to the west margin of Ordos basin for a long time, the provenance and tectonicsedimenary setting are still controversial. Based on the data analysis of sandstone detrital fragments, heavy mineral assemblages, geochemistry, composition of conglomerates, paleocurrent and tectonic deformation, it is indicated that the provenance and tectonicsediment setting is different in different areas in the west margin of Ordos basin. The deposition of the Upper Triassic in Helan Moutain occurred in craton, and its source areas belonged to the Alxa massif and Bayanhaote Basin, paleocurrent was from west to east, sedimentary setting is from fandelt to lake setting and Helan Moutain was rift basin in the Upper Triassic. The Upper Triassic sedimentation is tremendous, about 3 000 m in Shigouyi area.There are mainly feldspathic sandstone of this sedimentation, the provenance belonged to the Alxa massif, and paleocurrent was from northwest to southeast and Shigouyi area, and sedimentary setting was braidedriver setting. Shigouyi was downfaulted basin in Upper Triassic. The provenance belonged to QinlingQilianshan orogenic zone and stratum in CedipoHuating area, paleocurrent was from southwest to northeast, sedimentary setting was alluvial fan. CedipoHuating area was foreland basin in Upper Triassic. Based on the comprehensive analysis, it is suggested that the provenance and tectonicsedimentation was different in different areas in the west margin of Ordos basin, and being not uniform foreland basin simply.
Many geologists have paid attention to the west margin of Ordos basin for a long time, the provenance and tectonicsedimenary setting are still controversial. Based on the data analysis of sandstone detrital fragments, heavy mineral assemblages, geochemistry, composition of conglomerates, paleocurrent and tectonic deformation, it is indicated that the provenance and tectonicsediment setting is different in different areas in the west margin of Ordos basin. The deposition of the Upper Triassic in Helan Moutain occurred in craton, and its source areas belonged to the Alxa massif and Bayanhaote Basin, paleocurrent was from west to east, sedimentary setting is from fandelt to lake setting and Helan Moutain was rift basin in the Upper Triassic. The Upper Triassic sedimentation is tremendous, about 3 000 m in Shigouyi area.There are mainly feldspathic sandstone of this sedimentation, the provenance belonged to the Alxa massif, and paleocurrent was from northwest to southeast and Shigouyi area, and sedimentary setting was braidedriver setting. Shigouyi was downfaulted basin in Upper Triassic. The provenance belonged to QinlingQilianshan orogenic zone and stratum in CedipoHuating area, paleocurrent was from southwest to northeast, sedimentary setting was alluvial fan. CedipoHuating area was foreland basin in Upper Triassic. Based on the comprehensive analysis, it is suggested that the provenance and tectonicsedimentation was different in different areas in the west margin of Ordos basin, and being not uniform foreland basin simply.
2011, 29(3): 449-457.
Abstract:
Carbonate shoal develops in the middle part of Chihsia Formation at Shangsi Section of Guangyuan, Sichuan Province. The outcrop consists predominantly of thick bedded to massive limestone with intercalated dolostone. The rocks are light grey and crystalline, with some fossil fragments. Under microscope，abundant peloids and cortoids were identified. The peloids are classified into three types: fecal pellets, bahamite peloids and microbial peloids. The bahamite peloids are the most common grains observed. They are micritized bioclasts in origin, mainly including red algae, benthic foraminifera, crinoid and minor other shallow water organisms. Fossils are wellpreserved in some layers. In light of particle composition and preservation, these particles derived from organic hardparts within carbonate platform, and accumulated insitu, at least without major transportation. Intergranular porosities and organic cavities are filled mainly with sparry calcite cement with minor carbonate mud. Such a dominant sparry calcite cementation texture indicates the water energy was not strong enough to winnow off all the mud. Consequently, the peloidal shoal develops in relatively lowmedium energy environment. Microfacies types are is grouped into peloid packstonegrainstone，peloidcortoid grainstone，foraminiferaalgae packstone and bioclast wackstone. Based on grain type, sedimentary fabric and microfacies analysis, the peloidal shoal can be subdivided into shoal, shoal fringe and intershoal. In addition, such a peloidal shoal is widespread in the Permian strata of South China. Recognition of such a shoal and further study on its grain composition, depositional environment and spatial distribution will be of great significance on the understanding of Permian palaeogeographic framework of South China.
Carbonate shoal develops in the middle part of Chihsia Formation at Shangsi Section of Guangyuan, Sichuan Province. The outcrop consists predominantly of thick bedded to massive limestone with intercalated dolostone. The rocks are light grey and crystalline, with some fossil fragments. Under microscope，abundant peloids and cortoids were identified. The peloids are classified into three types: fecal pellets, bahamite peloids and microbial peloids. The bahamite peloids are the most common grains observed. They are micritized bioclasts in origin, mainly including red algae, benthic foraminifera, crinoid and minor other shallow water organisms. Fossils are wellpreserved in some layers. In light of particle composition and preservation, these particles derived from organic hardparts within carbonate platform, and accumulated insitu, at least without major transportation. Intergranular porosities and organic cavities are filled mainly with sparry calcite cement with minor carbonate mud. Such a dominant sparry calcite cementation texture indicates the water energy was not strong enough to winnow off all the mud. Consequently, the peloidal shoal develops in relatively lowmedium energy environment. Microfacies types are is grouped into peloid packstonegrainstone，peloidcortoid grainstone，foraminiferaalgae packstone and bioclast wackstone. Based on grain type, sedimentary fabric and microfacies analysis, the peloidal shoal can be subdivided into shoal, shoal fringe and intershoal. In addition, such a peloidal shoal is widespread in the Permian strata of South China. Recognition of such a shoal and further study on its grain composition, depositional environment and spatial distribution will be of great significance on the understanding of Permian palaeogeographic framework of South China.
2011, 29(3): 458-464.
Abstract:
Phylloid algal reefs are dominant in Pennsylvanian all over the world and well exposed in the south Guizhou, China. While the metazoan framework reefs develop well in this area, especially the presence of a rarely largescale Fomitchevella coral reef, which is constructed mostly by big phacelloid Fomitchevella. As a result, South Guizhou becomes a unique case of the Carboniferous reef. Stratigraphically, South Guizhou reefs belong to the Maping Formation (the Triticites Zone, Gzhelian, uppermost Pennsylvanian). The depositional environment of the Maping Formation is at shallow marine carbonate platform margin. Furthermore, the faunal association recorded point to a paleogeographical position in a lowlatitude close to the equatorial realm in south China during the Pennsylvanian time. Thus, it can be inferred that the growth environment of Fomitchevella reefs is in a relative warm water, fitting the development of coral reefs.
Surely we can use fossil brachiopod shells to attain part of environmental information with respect to the development of Pennsylvanian Fomitchevella coral reef in South Guizhou. These fossil brachiopod samples were collected from the uppermost Pennsylvanian Fomitchevella coral reef deposits in South Guizhou of China and the preservation state of shells was tested using conventional selection criteria such as cathodoluminescence, microscopy, trace element analysis and Xray diffraction analysis. Despite the selection of wellpreserved shells using the conventional evaluation criteria, there are still concerns as to whether the selected brachiopod shells do indeed contain original seawater signals. Analyzed insitu by Laser AblationInductively Coupled PlasmaMass Spectrometry（LAICPMS）, Fe, Mn, Ni, Sr, Na, Zn, Cr and Cd distribute symmetrically in shell transects of the fossil brachiopods
Striatifera striata and Enteletoides shuichengensis. Symmetry of the trace element distribution pattern derived from shell growth bands and is considered an intrinsic and original ontogenetic property of the brachiopod shell chemistry. Ni, Fe, Mn, Na and Sr distribution is symmetrical in the wellpreserved shells of the Pennsylvanian brachiopods Striatifera striata and Enteletoides shuichengensis, indicating that the selected shell by the conventional methods has preserved its original seawater signal for nearly 2.9 Ma. Pennsylvanian largescale Fomitchevella coral reef associated with brachiopods Striatifera striata and Enteletoides shuichengensis in the Triticites Zone, South Guizhou Province. Xray diffraction analysis indicates that the chemical composition of Striatifera striata shell is pure lowMg calcite and is free of any signs of diagenesis. Low Fe and Ni contents occurring in Enteletoides shuichengensis shell are indicative of slightly diagenetic alteration since recrystallization under reducing conditions tends to enrich shell calcite in Fe and Ni. Profiles of Ni, Fe, Mn, Na and Sr contents from hyperplasia symmetrically across the transverse section are nearly dissymmetrical in both brachiopod shells. Therefore, it supports a good preservation of both shells, and the diagenetic effect to fossil Enteletoides shuichengensis shell could be ignored. The carbon and oxygen isotopic composition of wellpreserved brachiopod shells were investigated in order to get some information with respect to the depositional environment of largesized Fomitchevella coral reef. The δ18OPDB values of Striatifera striata and Enteletoides shuichengensisis shells are -3.249‰ and -3.385‰ respectively, translated it into seasurface water temperatures of 21.60℃ to 31.18℃. These two brachiopod shells are high in δ13CPDB values of 4.784‰ and 4.782‰ respectively. The δ13CPDB values are slightly higher in comparison to values of Gzhelian brachiopods (+4.4±1.1‰) from the Russian platform. Z value was 135 point to “normal” marine values assumed for the Pennsylvanian coral reef seawater.
Phylloid algal reefs are dominant in Pennsylvanian all over the world and well exposed in the south Guizhou, China. While the metazoan framework reefs develop well in this area, especially the presence of a rarely largescale Fomitchevella coral reef, which is constructed mostly by big phacelloid Fomitchevella. As a result, South Guizhou becomes a unique case of the Carboniferous reef. Stratigraphically, South Guizhou reefs belong to the Maping Formation (the Triticites Zone, Gzhelian, uppermost Pennsylvanian). The depositional environment of the Maping Formation is at shallow marine carbonate platform margin. Furthermore, the faunal association recorded point to a paleogeographical position in a lowlatitude close to the equatorial realm in south China during the Pennsylvanian time. Thus, it can be inferred that the growth environment of Fomitchevella reefs is in a relative warm water, fitting the development of coral reefs.
Surely we can use fossil brachiopod shells to attain part of environmental information with respect to the development of Pennsylvanian Fomitchevella coral reef in South Guizhou. These fossil brachiopod samples were collected from the uppermost Pennsylvanian Fomitchevella coral reef deposits in South Guizhou of China and the preservation state of shells was tested using conventional selection criteria such as cathodoluminescence, microscopy, trace element analysis and Xray diffraction analysis. Despite the selection of wellpreserved shells using the conventional evaluation criteria, there are still concerns as to whether the selected brachiopod shells do indeed contain original seawater signals. Analyzed insitu by Laser AblationInductively Coupled PlasmaMass Spectrometry（LAICPMS）, Fe, Mn, Ni, Sr, Na, Zn, Cr and Cd distribute symmetrically in shell transects of the fossil brachiopods
Striatifera striata and Enteletoides shuichengensis. Symmetry of the trace element distribution pattern derived from shell growth bands and is considered an intrinsic and original ontogenetic property of the brachiopod shell chemistry. Ni, Fe, Mn, Na and Sr distribution is symmetrical in the wellpreserved shells of the Pennsylvanian brachiopods Striatifera striata and Enteletoides shuichengensis, indicating that the selected shell by the conventional methods has preserved its original seawater signal for nearly 2.9 Ma. Pennsylvanian largescale Fomitchevella coral reef associated with brachiopods Striatifera striata and Enteletoides shuichengensis in the Triticites Zone, South Guizhou Province. Xray diffraction analysis indicates that the chemical composition of Striatifera striata shell is pure lowMg calcite and is free of any signs of diagenesis. Low Fe and Ni contents occurring in Enteletoides shuichengensis shell are indicative of slightly diagenetic alteration since recrystallization under reducing conditions tends to enrich shell calcite in Fe and Ni. Profiles of Ni, Fe, Mn, Na and Sr contents from hyperplasia symmetrically across the transverse section are nearly dissymmetrical in both brachiopod shells. Therefore, it supports a good preservation of both shells, and the diagenetic effect to fossil Enteletoides shuichengensis shell could be ignored. The carbon and oxygen isotopic composition of wellpreserved brachiopod shells were investigated in order to get some information with respect to the depositional environment of largesized Fomitchevella coral reef. The δ18OPDB values of Striatifera striata and Enteletoides shuichengensisis shells are -3.249‰ and -3.385‰ respectively, translated it into seasurface water temperatures of 21.60℃ to 31.18℃. These two brachiopod shells are high in δ13CPDB values of 4.784‰ and 4.782‰ respectively. The δ13CPDB values are slightly higher in comparison to values of Gzhelian brachiopods (+4.4±1.1‰) from the Russian platform. Z value was 135 point to “normal” marine values assumed for the Pennsylvanian coral reef seawater.
2011, 29(3): 475-485.
Abstract:
The popular theory on texture classification of carbonates has not shed much light on the relict texture of dolomites, which is defined here as the texture remained of original limestone with >10% of grains after complete dolomitization and associated recrystallization, dissolution, fillings, and so on. It is emphasized for its important role in reconstructing the paleoenvironment of sedimentation. Based on whether most of the grains can be clearly and quantitatively distinguished with matrix and cements, and the inner texture of grains is preserved or not under microscope, the relict textures can be classified as the mimetic texture, the nonmimetic texture, and the ghost texture. These textures are described in detail with typical examples. The porosity classification of these relict textures should coincidently be refined after Choquette and Pray (1970). The pores are firstly classified as selective, partly selective or nonselective. Intragranular, intergranular, and intercrystal pores are selectively developed within individual grains, between grains, or between individual dolomite crystals, respectively. Furthermore, if the intercrystal pores are selectively developed within individual grains, then they are classified into intragranular and called intragranularintercrystal pores. Similarly there are intergranularintercrystal pores. Notably, moldic porosity hereby is also intragranular because they are always within individual grains. Partly selective pores in this case refer to dissolution enlarged intragranular, intergranular, or intercrystal pores. And the common nonselective pores are vugs, channels, caverns, fractures and breccia pores, as defined by Choquette and Pray (1970).
The popular theory on texture classification of carbonates has not shed much light on the relict texture of dolomites, which is defined here as the texture remained of original limestone with >10% of grains after complete dolomitization and associated recrystallization, dissolution, fillings, and so on. It is emphasized for its important role in reconstructing the paleoenvironment of sedimentation. Based on whether most of the grains can be clearly and quantitatively distinguished with matrix and cements, and the inner texture of grains is preserved or not under microscope, the relict textures can be classified as the mimetic texture, the nonmimetic texture, and the ghost texture. These textures are described in detail with typical examples. The porosity classification of these relict textures should coincidently be refined after Choquette and Pray (1970). The pores are firstly classified as selective, partly selective or nonselective. Intragranular, intergranular, and intercrystal pores are selectively developed within individual grains, between grains, or between individual dolomite crystals, respectively. Furthermore, if the intercrystal pores are selectively developed within individual grains, then they are classified into intragranular and called intragranularintercrystal pores. Similarly there are intergranularintercrystal pores. Notably, moldic porosity hereby is also intragranular because they are always within individual grains. Partly selective pores in this case refer to dissolution enlarged intragranular, intergranular, or intercrystal pores. And the common nonselective pores are vugs, channels, caverns, fractures and breccia pores, as defined by Choquette and Pray (1970).
2011, 29(3): 495-502.
Abstract:
Formation water is an important component of pore fluid. The space and time evolution of formation water is controlled by the hydrodynamic field and by fluidrock interaction, respectively, therefore, it is feasible to invert water rock interaction with the geochemical changes in ions and the combination relationships of different ions. In this paper, by systematical analysis of more than 300 formation water data from Upper Triassic Xujiahe Formation and Jurassic Formation in the middle area of West Sichuan Depression, the vertical geochemical variation characteristics of formation water and the corresponding waterrock interaction processes recorded by chemical characteristic was discussed preliminarily
The geochemical characteristics show that the cations of formation water are mainly K+, Na+, Ca2+, Mg2+, Fe2+, Fe3+, and the anions are mainly Cl, SO24, and HCO-3 in the study area. Main type of formation water with supplement of Na2SO4 and NaHCO3type is CaCl2 type.
From Jurassic to Xujiahe Formation in West Sichuan Depression, the formation water can be divided into 2 chemical zones: Obstructive replacing zone and Lagged zone. The zone affected by atmospheric water was only above 530 m.The formation water concentration decreased with depth as a result of largescale dehydration of clay minerals in obstructive replacing zone, but the main reasons for HCO-3 incensement with depth in this zone is addition of CO2 related to maturation of organic matter. The formation water in lagged zone has a significantly higher Ca2+ content than in obstructive replacing zone, which may be caused by albitization of feldspar. In addition, the dissolution of carbonate minerals may also have supplied some Ca2+ to lagged zone. From T3x4 to T3x2 HCO-3 concentration in formation water gradually become smaller, there may be two main reasons for the phenomenon above: First, T3x2 hydrocarbon source rocks had a relatively earlier hydrocarbon generation peak, the amount of CO2 injected into reservoir fluid was relatively smaller compared to T3x4; The other more likely reason was that stronger carbonate mineral dissolution in T3x4 than in T3x2 lead to major changes in HCO-3 concentration which was proved by relatively higher Ca2 + concentration in T3x4.
Na deficit ~ Ca2+ excess relationship showed that most of the Jurassic formation water samples were Na+ excess, indicating that Na+ was from dissolution of sodiumbearing minerals, and Ca2+ excess in formation water was caused by illitization of smectite and carbonate dissolution. Albitization of anorthite in Xujiahe Formation was an important waterrock interaction process, the other diagenetic types occurred in Xujiahe Formation included chloritization, dissolution of carbonate mineral and albite.
Formation water is an important component of pore fluid. The space and time evolution of formation water is controlled by the hydrodynamic field and by fluidrock interaction, respectively, therefore, it is feasible to invert water rock interaction with the geochemical changes in ions and the combination relationships of different ions. In this paper, by systematical analysis of more than 300 formation water data from Upper Triassic Xujiahe Formation and Jurassic Formation in the middle area of West Sichuan Depression, the vertical geochemical variation characteristics of formation water and the corresponding waterrock interaction processes recorded by chemical characteristic was discussed preliminarily
The geochemical characteristics show that the cations of formation water are mainly K+, Na+, Ca2+, Mg2+, Fe2+, Fe3+, and the anions are mainly Cl, SO24, and HCO-3 in the study area. Main type of formation water with supplement of Na2SO4 and NaHCO3type is CaCl2 type.
From Jurassic to Xujiahe Formation in West Sichuan Depression, the formation water can be divided into 2 chemical zones: Obstructive replacing zone and Lagged zone. The zone affected by atmospheric water was only above 530 m.The formation water concentration decreased with depth as a result of largescale dehydration of clay minerals in obstructive replacing zone, but the main reasons for HCO-3 incensement with depth in this zone is addition of CO2 related to maturation of organic matter. The formation water in lagged zone has a significantly higher Ca2+ content than in obstructive replacing zone, which may be caused by albitization of feldspar. In addition, the dissolution of carbonate minerals may also have supplied some Ca2+ to lagged zone. From T3x4 to T3x2 HCO-3 concentration in formation water gradually become smaller, there may be two main reasons for the phenomenon above: First, T3x2 hydrocarbon source rocks had a relatively earlier hydrocarbon generation peak, the amount of CO2 injected into reservoir fluid was relatively smaller compared to T3x4; The other more likely reason was that stronger carbonate mineral dissolution in T3x4 than in T3x2 lead to major changes in HCO-3 concentration which was proved by relatively higher Ca2 + concentration in T3x4.
Na deficit ~ Ca2+ excess relationship showed that most of the Jurassic formation water samples were Na+ excess, indicating that Na+ was from dissolution of sodiumbearing minerals, and Ca2+ excess in formation water was caused by illitization of smectite and carbonate dissolution. Albitization of anorthite in Xujiahe Formation was an important waterrock interaction process, the other diagenetic types occurred in Xujiahe Formation included chloritization, dissolution of carbonate mineral and albite.
2011, 29(3): 512-519.
Abstract:
Considering the production situations of meandering sand bodies at late high watercut stage under dense pattern condition in Daqing Sazhong development and based on the core analysis, well logging and production performance data, the method of hierarchy analysis combined with model matching was applied in subsurface architecture anatomy. The hierarchy analysis mentioned in this paper include the following: sedimentary unit dividing vertically, sedimentary facies dividing in the unit, single channel dividing, point bar or channel bar identifying in the channel sand and the study of the interlayer in the bar.
According to the results of reservoir modeling and numerical simulation, the different patterns of different development stage controlled by different hierarchy architecture elements were summarized at late high watercut stage under dense pattern condition. the three remaining oil distribution patterns of the meandering river reservoir controlled by different hierarchy architecture elements were summarized at late high watercut stage under dense pattern condition, which are triangleshaped remaining oil between point bars, ribbonshaped remaining oil created by abandon channel and flaplike remaining oil created by reservoir injectionproduction faultiness in point bar. Recovery measures for remaining oil controlled by lateral accretion shale bedding were proposed, which are subdivision and adjustment in interlayer, perfecting injectionproduction relation in single meandering belt and drilling horizontal wells on the top of the point bar.
The recovery measures for remaining oil controlled by lateral accretion shale bedding were proposed. The results show that the relationship of width/thickness ratio of sand body and lateral accretion interlayer's dip angel is well. The empirical formula could be used to predict dip angel of lateral accretion in meandering reservoir of Daqing placanticline. The efficiency of stochastic modeling is greatly improved with the automatic model matching method. The model can be numerical reservoir simulation. Simulation result show the distribution of interlayer remaining oil. This research finds that the different remaining oil should take different recovery measures.
Considering the production situations of meandering sand bodies at late high watercut stage under dense pattern condition in Daqing Sazhong development and based on the core analysis, well logging and production performance data, the method of hierarchy analysis combined with model matching was applied in subsurface architecture anatomy. The hierarchy analysis mentioned in this paper include the following: sedimentary unit dividing vertically, sedimentary facies dividing in the unit, single channel dividing, point bar or channel bar identifying in the channel sand and the study of the interlayer in the bar.
According to the results of reservoir modeling and numerical simulation, the different patterns of different development stage controlled by different hierarchy architecture elements were summarized at late high watercut stage under dense pattern condition. the three remaining oil distribution patterns of the meandering river reservoir controlled by different hierarchy architecture elements were summarized at late high watercut stage under dense pattern condition, which are triangleshaped remaining oil between point bars, ribbonshaped remaining oil created by abandon channel and flaplike remaining oil created by reservoir injectionproduction faultiness in point bar. Recovery measures for remaining oil controlled by lateral accretion shale bedding were proposed, which are subdivision and adjustment in interlayer, perfecting injectionproduction relation in single meandering belt and drilling horizontal wells on the top of the point bar.
The recovery measures for remaining oil controlled by lateral accretion shale bedding were proposed. The results show that the relationship of width/thickness ratio of sand body and lateral accretion interlayer's dip angel is well. The empirical formula could be used to predict dip angel of lateral accretion in meandering reservoir of Daqing placanticline. The efficiency of stochastic modeling is greatly improved with the automatic model matching method. The model can be numerical reservoir simulation. Simulation result show the distribution of interlayer remaining oil. This research finds that the different remaining oil should take different recovery measures.
2011, 29(3): 529-536.
Abstract:
Rare earth element concentrations were determined in 15 Middle Jurassic carbonate source rocks from Buqu Formation in Nadigangri area, Qiangtang basin of QinghaiTibet Plateau. The results show that analyses of the REEs, especially ΣREE,Ce/Ce* values and Eu/Eu* values change regularly,which are closely related to it’s sedimentary environment. The total REE contents (ΣREE) of Buqu Formation marine carbonate source rocks cover a range from 20.58 μg/g to 75.21 μg/g，and the average value of all samples is 36.67 μg/g. The NASC(North American Shale Composite) normalized REE patterns display low REE enrichments and relatively high REE loss, the LREE patterns are a little rightward heeling, and the HREE patterns are flat. However,the different ΣLREE and ΣHREE in the samples infer that REE was removed and HREE was more easily removed than LREE, sedimentary environment evolution may be in sound relationship with rising of the sea level rising. They all have slightly negative Ce anomalies(Ce/Ce* values are from 0.83 to 0.93,and the average is 0.88),most of them have slightly negative Eu anomalies ,and others have positive Eu anomalies(Eu/Eu* values are from 0.68 to 1.58,and most of them are less than 1).These features are probably due to the geochemistry of weak oxidation of sedimentary environment for Buqu Formation carbonate source rocks in Nadigangri area of Qiangtang basin, but with vertical variation of both sedimentary environment and water column stratification.Being the continuous of expansion of transgression and the water column's stratification effects, some water column in the bottom become into reducing environment for lacking of oxygen.
Rare earth element concentrations were determined in 15 Middle Jurassic carbonate source rocks from Buqu Formation in Nadigangri area, Qiangtang basin of QinghaiTibet Plateau. The results show that analyses of the REEs, especially ΣREE,Ce/Ce* values and Eu/Eu* values change regularly,which are closely related to it’s sedimentary environment. The total REE contents (ΣREE) of Buqu Formation marine carbonate source rocks cover a range from 20.58 μg/g to 75.21 μg/g，and the average value of all samples is 36.67 μg/g. The NASC(North American Shale Composite) normalized REE patterns display low REE enrichments and relatively high REE loss, the LREE patterns are a little rightward heeling, and the HREE patterns are flat. However,the different ΣLREE and ΣHREE in the samples infer that REE was removed and HREE was more easily removed than LREE, sedimentary environment evolution may be in sound relationship with rising of the sea level rising. They all have slightly negative Ce anomalies(Ce/Ce* values are from 0.83 to 0.93,and the average is 0.88),most of them have slightly negative Eu anomalies ,and others have positive Eu anomalies(Eu/Eu* values are from 0.68 to 1.58,and most of them are less than 1).These features are probably due to the geochemistry of weak oxidation of sedimentary environment for Buqu Formation carbonate source rocks in Nadigangri area of Qiangtang basin, but with vertical variation of both sedimentary environment and water column stratification.Being the continuous of expansion of transgression and the water column's stratification effects, some water column in the bottom become into reducing environment for lacking of oxygen.
2011, 29(3): 552-560.
Abstract:
From the profile which is located in the Hexi Corridor, NW China. 13 samples were collected for conventional 14C dating and 5 samples were collected for AMS 14C dating. The materials used for 14C dating were seeds, mud and wood. Based on the dating results, we reconstructed the age framework of Huahai Lake since the Late Glacial period. And then, we concluded that the sediments between 0.73～6.83 m were deposited during Holocene. Between
6.83~7.35 m, the sediments were deposited during the early Holocene and the late Younger Dryas.The sediments of 7.35~10.44 m were deposited during the Late Glacial and early Younger Dryas. Based on the mineral analysis of the sediments during the Younger Dryas and late glacial, mirabilite was the main component in the sediments, indicating the lowtemperature environment. According to the chemical composition analysis , the main ingredient of the pure mirabilite deposition is Na2SO4 ·10H2O, which is an indicator of the colddry environment; and the lower the temperature is good for the mineral crystallizing processes. The solubility curve of SO24 in Na2SO4NaClH2O indicated that, in low surrounding temperature, the concentration of SO24 was lower in saturation Na2SO4, and simply increasing the lake level could not improve the ability of mirabilite solution, which was not powerful enough to break off the deposition. The main reason of the interruption for mirabilite deposition may be transient warming events. Therefore, the rhythm deposition formation of mirabilitesiltmirabilite indicated the periodic changes of temperature during the late glacial and the Younger Dryas. According to the characteristics of the sediments and lithology, we reconstructed the millenniumscale effective moisture conditions during the Holocene period. Before 10.47 cal ka BP, the sediments color appears dark brown, purple brownbased, indicating a typical oxidizing environment,and this oxidative environment can not appear in the deep lake environment. There are no obvious lacustrine depositions layers at the beginning of Holocene（before10.4 cal ka BP）, 6.30~3.73 m, and instead the layers are formed mainly on alluvial and eolian depositions, while the eolian depositions layers sandwiched between two alluvial depositions layers.The climate was relatively arid, and the alluvial and aeolian sediments prevailed during this period. Between 10.47 cal ka BP and 8.87 cal ka BP, the climate changed from arid to humid. During 8.87~5.5 cal ka BP the lake was relatively deep, and the climate was relatively humid. From 5.5 cal ka BP, there was little sediment in the section, showing that the lake became to dry up since then. This Holocene environmental change in millenniumscale was different from the westerlies in the arid Central Asian areas, but it was not the same as the environmental change in the eastern part of China, which was controlled by Asian monsoon. So the Holocene environment of the Huahai Lake region was affected by the Westerlies and the East Asian monsoon.
From the profile which is located in the Hexi Corridor, NW China. 13 samples were collected for conventional 14C dating and 5 samples were collected for AMS 14C dating. The materials used for 14C dating were seeds, mud and wood. Based on the dating results, we reconstructed the age framework of Huahai Lake since the Late Glacial period. And then, we concluded that the sediments between 0.73～6.83 m were deposited during Holocene. Between
6.83~7.35 m, the sediments were deposited during the early Holocene and the late Younger Dryas.The sediments of 7.35~10.44 m were deposited during the Late Glacial and early Younger Dryas. Based on the mineral analysis of the sediments during the Younger Dryas and late glacial, mirabilite was the main component in the sediments, indicating the lowtemperature environment. According to the chemical composition analysis , the main ingredient of the pure mirabilite deposition is Na2SO4 ·10H2O, which is an indicator of the colddry environment; and the lower the temperature is good for the mineral crystallizing processes. The solubility curve of SO24 in Na2SO4NaClH2O indicated that, in low surrounding temperature, the concentration of SO24 was lower in saturation Na2SO4, and simply increasing the lake level could not improve the ability of mirabilite solution, which was not powerful enough to break off the deposition. The main reason of the interruption for mirabilite deposition may be transient warming events. Therefore, the rhythm deposition formation of mirabilitesiltmirabilite indicated the periodic changes of temperature during the late glacial and the Younger Dryas. According to the characteristics of the sediments and lithology, we reconstructed the millenniumscale effective moisture conditions during the Holocene period. Before 10.47 cal ka BP, the sediments color appears dark brown, purple brownbased, indicating a typical oxidizing environment,and this oxidative environment can not appear in the deep lake environment. There are no obvious lacustrine depositions layers at the beginning of Holocene（before10.4 cal ka BP）, 6.30~3.73 m, and instead the layers are formed mainly on alluvial and eolian depositions, while the eolian depositions layers sandwiched between two alluvial depositions layers.The climate was relatively arid, and the alluvial and aeolian sediments prevailed during this period. Between 10.47 cal ka BP and 8.87 cal ka BP, the climate changed from arid to humid. During 8.87~5.5 cal ka BP the lake was relatively deep, and the climate was relatively humid. From 5.5 cal ka BP, there was little sediment in the section, showing that the lake became to dry up since then. This Holocene environmental change in millenniumscale was different from the westerlies in the arid Central Asian areas, but it was not the same as the environmental change in the eastern part of China, which was controlled by Asian monsoon. So the Holocene environment of the Huahai Lake region was affected by the Westerlies and the East Asian monsoon.
2011, 29(3): 572-579.
Abstract:
The South China Sea is the largest marginal sea in the western Pacific Ocean and its' north and south are wide continental shelf. There are many rivers flow into the South China Sea. The highresolution sediment records abundant environmental information of land and sea. This area has become one of hotspots on paleoceanography research and made a lot of research results. Planktonic foraminifera are very sensitive to changes of marine environment. Sea water temperature changes can directly affect the migration and succession of biota. Therefore, research the distribution of planktonic foraminifera in core sediment to analyze the evolution of paleoclimate. In this paper, a sediment Core N31 located in the northern South China Sea had been researched including quantitative analysis and identification of planktonic foraminifera, oxygen and carbon isotopes, carbonate content and grain size, AMS14C dating, sea surface temperature and thermocline depth calculated by paleoecological transfer function. The following conclusions have been attained:
1) The bottom age of Core N31 was about 55ka BP and this core accepted deposition since marine isotope stage 3.
2) Planktonic foraminifera species analysis showed that changes in abundance as the glacialinterglacial cycles and change. Tropical and subtropical species appeared in lager numbers in interglacial and its maximum percentage in MIS3 or MIS1, but temperate species appeared in larger numbers in the glacial period.
3) The sea surface temperature (SST) estimated by the transfer function FP12E shows that the summer SST ranges from 27.0 to 29.6℃ and the winter SST from 18.2 to 27.0℃. The comparison of SST data between the southern and northern SCS shows that SST in the southern SCS is higher than that in the northern SCS. The SST difference is more obvious in winter.
4) The thermocline data show no obvious fluctuations during MIS3MIS2, but the depth deepened gradually during the transitional period from the glacial to the postglacial.
The South China Sea is the largest marginal sea in the western Pacific Ocean and its' north and south are wide continental shelf. There are many rivers flow into the South China Sea. The highresolution sediment records abundant environmental information of land and sea. This area has become one of hotspots on paleoceanography research and made a lot of research results. Planktonic foraminifera are very sensitive to changes of marine environment. Sea water temperature changes can directly affect the migration and succession of biota. Therefore, research the distribution of planktonic foraminifera in core sediment to analyze the evolution of paleoclimate. In this paper, a sediment Core N31 located in the northern South China Sea had been researched including quantitative analysis and identification of planktonic foraminifera, oxygen and carbon isotopes, carbonate content and grain size, AMS14C dating, sea surface temperature and thermocline depth calculated by paleoecological transfer function. The following conclusions have been attained:
1) The bottom age of Core N31 was about 55ka BP and this core accepted deposition since marine isotope stage 3.
2) Planktonic foraminifera species analysis showed that changes in abundance as the glacialinterglacial cycles and change. Tropical and subtropical species appeared in lager numbers in interglacial and its maximum percentage in MIS3 or MIS1, but temperate species appeared in larger numbers in the glacial period.
3) The sea surface temperature (SST) estimated by the transfer function FP12E shows that the summer SST ranges from 27.0 to 29.6℃ and the winter SST from 18.2 to 27.0℃. The comparison of SST data between the southern and northern SCS shows that SST in the southern SCS is higher than that in the northern SCS. The SST difference is more obvious in winter.
4) The thermocline data show no obvious fluctuations during MIS3MIS2, but the depth deepened gradually during the transitional period from the glacial to the postglacial.
2011, 29(3): 580-586.
Abstract:
Zhenwu oilfield, located at the midsouthern part of Gaoyou Sag of Subei basin, is the largest oil field that has been discovered in Subei basin, which has the characteristics of developed long, large oilbearing area and high enrichingoil degree. The oilfield is located at the downthrow block of Zhen 2 fault in the southern part of the deep sag, and it is to hydrocarbon generating sags.The oil mainly distributes in three layers including the first member of the Sanduo Formation, the first & second member of the Dainan Formation. Some petroleum also distributed in the first member of the Funing Formation. Reservoir rocks are mostly fine sandstone and anisometric sandstone. Combining with various geological features, the authors analyse accumulation period and the dynamic accumulation process of Zhenwu oil field by ways of structural evolution, crude oil features and fluid inclusion. The structural evolution history shows that fault activity is strong from Dainan Formation deposition to early Yancheng Deposition. Earth crust uplifted and formation eroded resulted in serious destruction of oil reservoir at the late of Sanduo Formation, then fault continued activity and petroleum migration. The sag continued to accept deposition and fault activity stops at the late of Yancheng Formation deposition, and the petroleum migration rate slowed down. It is favorable for petroleum reservation when the formation thickness was big at the late deposition.
From the source rock evolution history , there are two times of petroleum generation during which the source rock of the second member of the Funing Formation enter the sag is at a great quantity of petroleum generation at the late and last stage of Sanduo Formation when the source rock of the fourth member of the Funing Formation had not reached oil threshold and only generated a little petroleum, so it was the oil mainly generated by the source rock of the second member of the Funing Formation. But most of the reservoirs were damaged by the influence of the regional tectonic activities at the late of Sanduo period. When the Yancheng Formation was depositing, the source rock of second & fourth member of the Funing Formation again reached maturation which result in secondary hydrocarbon generation.
Meantime, the characteristics of fluid inclusions in Zhenwu oil field show that it mainly developed one phase of fluid inclusion which organic inclusion and its associated brine inclusion mostly develop at the quartz secondary outgrowth cementation and there is only one peak temperature area. Associated with burial history of individual well, the authors find that the time of petroleum migration and accumulation was the time of the second member of Sanduo Formation deposition which had a certain difference with accumulation time inverted by structural evolution and source rock evolution. At last, with the analysis of petroleum dynamic accumulation process by ways of accumulation periods, the authors reach conclusion that there were two accumulation periods in Zhenwu oilfield, firstly, the second member of the Funing Formation generated, migrated and accumulated before the late of Sanduo Formation, but the next structural uplift at the late of Sanduo Formation damaged the early oil reservoirs. At the EarlyMiddle of Yancheng Formation, it mainly is the time of the fourth member of the Funing Formation reburied and secondary oil generation, which is the essential period of petroleum migration and accumulation. From the the late of Yancheng Formation on, it is the essential period of petroleum preservation.
Zhenwu oilfield, located at the midsouthern part of Gaoyou Sag of Subei basin, is the largest oil field that has been discovered in Subei basin, which has the characteristics of developed long, large oilbearing area and high enrichingoil degree. The oilfield is located at the downthrow block of Zhen 2 fault in the southern part of the deep sag, and it is to hydrocarbon generating sags.The oil mainly distributes in three layers including the first member of the Sanduo Formation, the first & second member of the Dainan Formation. Some petroleum also distributed in the first member of the Funing Formation. Reservoir rocks are mostly fine sandstone and anisometric sandstone. Combining with various geological features, the authors analyse accumulation period and the dynamic accumulation process of Zhenwu oil field by ways of structural evolution, crude oil features and fluid inclusion. The structural evolution history shows that fault activity is strong from Dainan Formation deposition to early Yancheng Deposition. Earth crust uplifted and formation eroded resulted in serious destruction of oil reservoir at the late of Sanduo Formation, then fault continued activity and petroleum migration. The sag continued to accept deposition and fault activity stops at the late of Yancheng Formation deposition, and the petroleum migration rate slowed down. It is favorable for petroleum reservation when the formation thickness was big at the late deposition.
From the source rock evolution history , there are two times of petroleum generation during which the source rock of the second member of the Funing Formation enter the sag is at a great quantity of petroleum generation at the late and last stage of Sanduo Formation when the source rock of the fourth member of the Funing Formation had not reached oil threshold and only generated a little petroleum, so it was the oil mainly generated by the source rock of the second member of the Funing Formation. But most of the reservoirs were damaged by the influence of the regional tectonic activities at the late of Sanduo period. When the Yancheng Formation was depositing, the source rock of second & fourth member of the Funing Formation again reached maturation which result in secondary hydrocarbon generation.
Meantime, the characteristics of fluid inclusions in Zhenwu oil field show that it mainly developed one phase of fluid inclusion which organic inclusion and its associated brine inclusion mostly develop at the quartz secondary outgrowth cementation and there is only one peak temperature area. Associated with burial history of individual well, the authors find that the time of petroleum migration and accumulation was the time of the second member of Sanduo Formation deposition which had a certain difference with accumulation time inverted by structural evolution and source rock evolution. At last, with the analysis of petroleum dynamic accumulation process by ways of accumulation periods, the authors reach conclusion that there were two accumulation periods in Zhenwu oilfield, firstly, the second member of the Funing Formation generated, migrated and accumulated before the late of Sanduo Formation, but the next structural uplift at the late of Sanduo Formation damaged the early oil reservoirs. At the EarlyMiddle of Yancheng Formation, it mainly is the time of the fourth member of the Funing Formation reburied and secondary oil generation, which is the essential period of petroleum migration and accumulation. From the the late of Yancheng Formation on, it is the essential period of petroleum preservation.
2011, 29(3): 593-598.
Abstract:
Using gas chromatographymass spectrometer analyzed biological markers of Changcheng System Gaoyuzhuang Group (Chg) limestone and Jixian System Hongshuizhuang Group (Jxh) shale both outcrop and core, which are collected from Jibei depression in Yanshan
area. Gaoyuzhuang (Chg) limestone and Hongshuizhuang group (Jxh) mudstone alkanes and diterpenoid biomarkers comparison shows the genetic source from the plankton and the benthic pelagic zooplankton class to plankton and depositional environment changed from high salinity to lower process. Outcrop samples and the corresponding core in the comparison of biological markers in the area show the role of environmental factors such as the weathering affecting less of hopane biomarkers, while affecte the nalkane distribution patterns and the distribution of steranes larger. Occurrence of limestone samples of different biomarker little change, and shale in the bonding state relative to states with high content of free longchain nalkanes. The results showed that limestone has a high number of parcels in the state of organic matter, acid treated shale has a relatively high content of high molecular weight nalkanes released, indicating acidic environment can reduce the shale adsorption capacity of organic matter and destroy organic clay complex.
Using gas chromatographymass spectrometer analyzed biological markers of Changcheng System Gaoyuzhuang Group (Chg) limestone and Jixian System Hongshuizhuang Group (Jxh) shale both outcrop and core, which are collected from Jibei depression in Yanshan
area. Gaoyuzhuang (Chg) limestone and Hongshuizhuang group (Jxh) mudstone alkanes and diterpenoid biomarkers comparison shows the genetic source from the plankton and the benthic pelagic zooplankton class to plankton and depositional environment changed from high salinity to lower process. Outcrop samples and the corresponding core in the comparison of biological markers in the area show the role of environmental factors such as the weathering affecting less of hopane biomarkers, while affecte the nalkane distribution patterns and the distribution of steranes larger. Occurrence of limestone samples of different biomarker little change, and shale in the bonding state relative to states with high content of free longchain nalkanes. The results showed that limestone has a high number of parcels in the state of organic matter, acid treated shale has a relatively high content of high molecular weight nalkanes released, indicating acidic environment can reduce the shale adsorption capacity of organic matter and destroy organic clay complex.
2011, 29(3): 605-612.
Abstract:
Tahe oilfield locates in the southwest part of Akekule uplift of Shaya uplift in Tarim basin. So far Tahe Oilfield is the largest marine limestone oilfield of China. In spite of abundant geological and geochemical research efforts are carried in the oilfield but some kinds of doubtful points are not resolved for example the main source rocks, parent material and hydrocarbon accumulation period. Oil samples come from new developed oilwells of Tahe oilfield. According to the systems analysis and high precision GCMS analysis, this paper studied the distributional characteristics biomarkers, oil and source rock correlation, and genetic type of oils. The geochemical characteristics of saturated hydrocarbon we can know that the oils from Tahe oilfield have higher maturity, kerogen type is homonemeae, the oils form from marine reducing environment, and the oils suffer some kind of biodegradation. The predominance of C29 sterane is related to pelagic green algae and macro body brown algae. The detection of Dinoflagellate sterane and 4methyl sterane show the contribution of dinoflagellate and bacteria. Tricyclic terpane and tetracyclic terpane parameters show that they are marine crude oils. The maturity of oils from Triassic and Carboniferous are higher than Ordovician crude oils. The distributional characteristics of pentacyclic triterpane indicate the contribution of homonemeae. Gammacerane /αβC30hopane and the content of >C30hopane show that the oils originated from salinity marine environment. C29sterane 20S/(20S+20R) and ββ/(αα+ββ) are 0.470.52 and 0.490.58 indicate that the oils are mature crude oils. The main source rocks of Tahe oilfield is a controversial problem. According to the relative content of C27, C28 and C29sterane This paper discussed the source rock of Tahe oilfield. The results show that middle and upper ordovician source rocks are chief source rocks, and also lower Ordovician and Cambrian source rocks have some kinds of contribution to highmaturity oil. The oil reservoirs have characteristics of hydrocarbon accumulation multiperiod. Above the study result will offer scientific reference for the exploration and develop of this kind of oilfield.
Tahe oilfield locates in the southwest part of Akekule uplift of Shaya uplift in Tarim basin. So far Tahe Oilfield is the largest marine limestone oilfield of China. In spite of abundant geological and geochemical research efforts are carried in the oilfield but some kinds of doubtful points are not resolved for example the main source rocks, parent material and hydrocarbon accumulation period. Oil samples come from new developed oilwells of Tahe oilfield. According to the systems analysis and high precision GCMS analysis, this paper studied the distributional characteristics biomarkers, oil and source rock correlation, and genetic type of oils. The geochemical characteristics of saturated hydrocarbon we can know that the oils from Tahe oilfield have higher maturity, kerogen type is homonemeae, the oils form from marine reducing environment, and the oils suffer some kind of biodegradation. The predominance of C29 sterane is related to pelagic green algae and macro body brown algae. The detection of Dinoflagellate sterane and 4methyl sterane show the contribution of dinoflagellate and bacteria. Tricyclic terpane and tetracyclic terpane parameters show that they are marine crude oils. The maturity of oils from Triassic and Carboniferous are higher than Ordovician crude oils. The distributional characteristics of pentacyclic triterpane indicate the contribution of homonemeae. Gammacerane /αβC30hopane and the content of >C30hopane show that the oils originated from salinity marine environment. C29sterane 20S/(20S+20R) and ββ/(αα+ββ) are 0.470.52 and 0.490.58 indicate that the oils are mature crude oils. The main source rocks of Tahe oilfield is a controversial problem. According to the relative content of C27, C28 and C29sterane This paper discussed the source rock of Tahe oilfield. The results show that middle and upper ordovician source rocks are chief source rocks, and also lower Ordovician and Cambrian source rocks have some kinds of contribution to highmaturity oil. The oil reservoirs have characteristics of hydrocarbon accumulation multiperiod. Above the study result will offer scientific reference for the exploration and develop of this kind of oilfield.
2011, 29(3): 440-448.
Abstract:
Early Triassic Yangtze platform was located in the northeastern margin of Tethys. Based upon the large amount of geological evidence and simulation experiments, researchers confirmed that the Triassic climate system was megamonsoon that controlled the climate of whole Pangaea and surrounding sea. However abundant outcrops of Triassic strata in our country, whether contained some information implying monsoon climate? We found a set of wellpreserved tempestite in the Lower Triassic at Shangsi Section, Guangyuan city, northwest Sichuan, which developed in the lower part of the Feixianguan Formation. The sedimentary characteristics of Lower Triassic Tempestite was significant, including stormgenerated gravel, storm erosion structures, storm tear structures and bedding structures. Gravel was composed of micritic limestone, and might be divided into two types according to roundness. One contained brecciated, strip, axiolitic shape; the other presented flatgravel shape. Storm erosion structures included pocket and chrysanthemum shape formed by drainage and channel mode, erosion surface structure. Storm tear structures included messy mud gravel, torn sutureline breccia and truncated structure amongst lays. Bedding structures included hummocky cross bedding, graded bedding,blocky bedding ,homogeneous bedding and parallel bedding. According to sedimentary structures and lithology, three kinds of sequence of SaSbSc, SbSd, SaScSd(Sastranded gravel deposition, Sbgraded bedding, Schummocky crossstratification, Sdhomogeneous bedding) were recognized. The storm deposits occurred in the shallow sea and the formation, development and characteristics of the tempestites have important significance on paleoclimate research. We think that tempstite in Shangsi (and even whole UpperYangtze region) was controlled likely by the strong monsoon system (Megamonsoon) in Early Triassic, and the P/T boundary mass extinction event let tempestite be preserved below the setting that organism burrows were few.
Early Triassic Yangtze platform was located in the northeastern margin of Tethys. Based upon the large amount of geological evidence and simulation experiments, researchers confirmed that the Triassic climate system was megamonsoon that controlled the climate of whole Pangaea and surrounding sea. However abundant outcrops of Triassic strata in our country, whether contained some information implying monsoon climate? We found a set of wellpreserved tempestite in the Lower Triassic at Shangsi Section, Guangyuan city, northwest Sichuan, which developed in the lower part of the Feixianguan Formation. The sedimentary characteristics of Lower Triassic Tempestite was significant, including stormgenerated gravel, storm erosion structures, storm tear structures and bedding structures. Gravel was composed of micritic limestone, and might be divided into two types according to roundness. One contained brecciated, strip, axiolitic shape; the other presented flatgravel shape. Storm erosion structures included pocket and chrysanthemum shape formed by drainage and channel mode, erosion surface structure. Storm tear structures included messy mud gravel, torn sutureline breccia and truncated structure amongst lays. Bedding structures included hummocky cross bedding, graded bedding,blocky bedding ,homogeneous bedding and parallel bedding. According to sedimentary structures and lithology, three kinds of sequence of SaSbSc, SbSd, SaScSd(Sastranded gravel deposition, Sbgraded bedding, Schummocky crossstratification, Sdhomogeneous bedding) were recognized. The storm deposits occurred in the shallow sea and the formation, development and characteristics of the tempestites have important significance on paleoclimate research. We think that tempstite in Shangsi (and even whole UpperYangtze region) was controlled likely by the strong monsoon system (Megamonsoon) in Early Triassic, and the P/T boundary mass extinction event let tempestite be preserved below the setting that organism burrows were few.
2011, 29(3): 465-474.
Abstract:
The carbonate karst reservoir in YingmailiHalahatang area which gained breakthrough recently in Tarim Basin was controlled by lithology, karstification and tectonic evolution. So, it is very important to study the characteristics and genesis of the reservoir for the exploration and development. Based on the cores, normal thin sections, cast thin sections, cathodoluminescence, FMI and testing data, the protopores and permeability of the Ordovician carbonate karst reservoir in the study area were poor, and it's difficult to form favorable reservoir space. However, the second pores, for example, solution pores, cavities and fractures constitute the main reservoir space, and their heterogeneity in the vertical and horizontal distribution is very strong. Reservoir space according to the combination of characteristics of the Ordovician reservoir is divided into four categories: vuggy, fracturevuggy, cavern, fracture. The types of Yingmaili area are mostly fracture and fracturecavern, while the types of Halahatang area are vuggy and fracturevuggy. Overall, fracturevuggy and vuggy reservoir developed preponderantly, and they were the most excellent reservoir. Penecontemporaneous karstification, intrastrata karstification, alongstrata karstification, buriedhill karstification, burial dissolution was the main genesis of the carbonate karst reservoir in YingmailiHalahatang area. And complex and pronounced superimposed karstification made the reservoir finally becoming potential excellent one. During the depositional period of the shortterm cyclical falling in sea level, the unconsolidated carbonate sediment on the high parts of the ancient landscape exposed over the sea level to form a fabric choice of porous layer stack for further transformation of karstification as a foundation by the affection of fresh water dissolution. At the end of the Yijianfang Formation and Lianglitage Formation, Tabei area was uplifted as a whole by compression structure of Tarim Basin, making the stratified rock exposed on the surface, and controlled by the intrastrata karstification, a large number of nonfabric selective dissolution pores and dissolved fracture were formed in the depth of 130 meters under exposed surface of the top of Yijianfang Formation, and becoming an important reservoir intervals. Before Silurian sedimentation, Tabei uplift as a whole exposed on the surface, making the study area with varying degrees of erosion. The area on the north of Sangtamu pinchout underwent buriedhill karstification forming fractured reservoir. Meanwhile, the area on the south of Sangtamu pinchout underwent alongstrata karstification with porous layer by early penecontemporaneous karstification and intrastrata karstification, and the buriedhill region was the fresh water supply source, and these made the reservoir of the region being optimized. After Hercynian, the reservoir buried in a shallowdeep relatively closed diagenesis environment, the interaction between the acid stratum water and the rock under longterm buried environment resulted from of diagenesis differed from that resulted in the fresh water and marine environment, and burial dissolution occurred with cementation, and that made the early reservoir reconstructed to further increase the heterogeneity of the reservoir. Some of the high angle fractures and net tiny fractures during the Himalayan which were mostly unfilled adjusted the reservoir with a certain contribution. With the study of karstification process, it is pointed that the protopores and the sedimentary facies were the basic factors of second pores forming, and karstifications were the main factors which controlled the reservoir development, and fractures during the tectonic evolution were the key factors which accelerated the reservoir development and controlled its distribution.
The carbonate karst reservoir in YingmailiHalahatang area which gained breakthrough recently in Tarim Basin was controlled by lithology, karstification and tectonic evolution. So, it is very important to study the characteristics and genesis of the reservoir for the exploration and development. Based on the cores, normal thin sections, cast thin sections, cathodoluminescence, FMI and testing data, the protopores and permeability of the Ordovician carbonate karst reservoir in the study area were poor, and it's difficult to form favorable reservoir space. However, the second pores, for example, solution pores, cavities and fractures constitute the main reservoir space, and their heterogeneity in the vertical and horizontal distribution is very strong. Reservoir space according to the combination of characteristics of the Ordovician reservoir is divided into four categories: vuggy, fracturevuggy, cavern, fracture. The types of Yingmaili area are mostly fracture and fracturecavern, while the types of Halahatang area are vuggy and fracturevuggy. Overall, fracturevuggy and vuggy reservoir developed preponderantly, and they were the most excellent reservoir. Penecontemporaneous karstification, intrastrata karstification, alongstrata karstification, buriedhill karstification, burial dissolution was the main genesis of the carbonate karst reservoir in YingmailiHalahatang area. And complex and pronounced superimposed karstification made the reservoir finally becoming potential excellent one. During the depositional period of the shortterm cyclical falling in sea level, the unconsolidated carbonate sediment on the high parts of the ancient landscape exposed over the sea level to form a fabric choice of porous layer stack for further transformation of karstification as a foundation by the affection of fresh water dissolution. At the end of the Yijianfang Formation and Lianglitage Formation, Tabei area was uplifted as a whole by compression structure of Tarim Basin, making the stratified rock exposed on the surface, and controlled by the intrastrata karstification, a large number of nonfabric selective dissolution pores and dissolved fracture were formed in the depth of 130 meters under exposed surface of the top of Yijianfang Formation, and becoming an important reservoir intervals. Before Silurian sedimentation, Tabei uplift as a whole exposed on the surface, making the study area with varying degrees of erosion. The area on the north of Sangtamu pinchout underwent buriedhill karstification forming fractured reservoir. Meanwhile, the area on the south of Sangtamu pinchout underwent alongstrata karstification with porous layer by early penecontemporaneous karstification and intrastrata karstification, and the buriedhill region was the fresh water supply source, and these made the reservoir of the region being optimized. After Hercynian, the reservoir buried in a shallowdeep relatively closed diagenesis environment, the interaction between the acid stratum water and the rock under longterm buried environment resulted from of diagenesis differed from that resulted in the fresh water and marine environment, and burial dissolution occurred with cementation, and that made the early reservoir reconstructed to further increase the heterogeneity of the reservoir. Some of the high angle fractures and net tiny fractures during the Himalayan which were mostly unfilled adjusted the reservoir with a certain contribution. With the study of karstification process, it is pointed that the protopores and the sedimentary facies were the basic factors of second pores forming, and karstifications were the main factors which controlled the reservoir development, and fractures during the tectonic evolution were the key factors which accelerated the reservoir development and controlled its distribution.
2011, 29(3): 486-494.
Abstract:
The microtopography difference of the epeiric carbonate platform in the depositional stage is so tiny,as a result,it is too hard to identify.This paper is then,firstly,mainly based on the development dominating factors of the grain shoal within the platform,and then points out that the microtopography highland tends to be beyond the wave base in the relativeregression stage,where the grain shoal develops.The depositional rate is higher than any other microfacies area within the platform,hence,the topography difference was enhanced at that stage.Besides,after the sedimentation of the grain shoal,the grainsupported framework forms under the influence of physical compaction,where the compaction rate is much lower than the finer sediments,so the depositional thickness resulted from the topography difference of various microfacies areas is also further enhanced,which shows that the grainstone thickness within a certain period of time can be used, approximately,in recovering its microtopography prominence when it began to present, and that the compaction correction can be ignored when approximately recovering the microtopography within the platform at the depositional stage.It then further analyses the effects on the grain shoal construction and reservoir development by the exposure process during the depositional stage,and it divides the shoal within the epeiric platform into three genetic types:unexposed shoal,shortmediumterm exposed shoal and longterm exposed shoal, meanwhile,pointing out that the method of grainstone grossthickness which is used,approximately,in recovering the depositional palaeogeomorphology of epeiric carbonate platform is preferable for the unexposed and shortmediumterm exposed shoals,where the main characteristics of the shortmedium term exposed shoal can be concluded as follows(contrarily be longterm exposure ):①unconformity characteristic limited,palaeosol lacks;②irregular karren and corroded fissure lack;③intargranular solution extremely develops;④the freshwater cements in early stage and cement unconformity exist;⑤lensdiagenesis reservoir of atmospheric genesis positively associates with the grainstone grossthickness.Based on this,the paper then takes the view that microtopography prominence can be inverted by the reservoir study of the grain shoal.Followed by that principle,it also suggestes that the concrete study procedure can be like this:the isochronous geologic body to be chosen as the main body of grainstone deposition,the confirmation of reservoir genesis and exposured time,the topography recovering during depositional stage and the application of achievement verification.
Sichuan Basin was characterized by developing epeiric carbonate platform during the period of Jialingjiang in early Triassic.The basin was also hit by an fierce transgression in the period of early Jia 22, which made the salinity of the seawater normal on the whole.Moxi gas field locates in the south of gentleoblique tectonic zone of the palaeohigh in the central of the basin,where the tectonic body is about 280 km2, and the exploration wells penetrating the Jia 2 member sum up to 42(data by 2005),of which the total cored wells of Jia 2 member sum up to 16,besides, the distribution is relatively uniform.Hence,the gas field was used in the case study,where the result indicates that highland mainly develop in the well areas of eastern side of Mo 24Mo 205,southern side of Mo 206,the rim of Mo 207,Mo 151Mo 36,Mo 208 and its southern part,Mo 48,Northern part of Mo 202(7 in all),which distribute in the direction of southwestnortheast,swales mainly develop in Mo 12Mo 201,Mo 0052Mo 150,southern part of Mo 22 and eastern part of Mo 206.There is thick deposition of underwatergypsum(darkgray and massive gypsum,no exposed marks found) developing in the well areas of Mo 0052Mo 150,Mo 207,which has come into being by the shoal development around the microhighland ,resulting in the sealing restrict of the lowlying environment of interbank sea and the evaporation and concentation of the waterbody,the gypsum deposition therefore comes into being.It can be believed from the above that the recovery of the palaeogeomorphology by taking advantage of the grainstone thickness can be supported by the lithofacies deposition.
According to the graph of sedimentary facies compiled by actual cored data of B Formation,Jia 22 Submember, the palaeogeomorphology during early sedimentary stage carries on developing in the stage of Jia 22B.dominating the distributing framework of its sedimentation and reservoir.The result indicates that this sort of method used in recovering the microtopography during depositional stage is applied to the characteristics of lithofacies and so on.,besides,the recovered microtopography in the sedimentary stage can not only continue to successively develop over a long period of time and can also dominate the deposition of adjacent stratigraphy and the framework of reservoir distribution,furthermore,relatively speaking,its production application effect is good,which also indicates that dedicate description of sedimentation and reservoir is an effective and adjuvant measure for those gas fields at developing stage with high density of well pattern and that this kind of method should be widely popularized,especially for those maturing basin fields with high level of well exploration,data that is out of date, rare triporosity logging series,all of these are significant and also has referenced significance for the reservoir prediction and tapping the new potential formation.
The microtopography difference of the epeiric carbonate platform in the depositional stage is so tiny,as a result,it is too hard to identify.This paper is then,firstly,mainly based on the development dominating factors of the grain shoal within the platform,and then points out that the microtopography highland tends to be beyond the wave base in the relativeregression stage,where the grain shoal develops.The depositional rate is higher than any other microfacies area within the platform,hence,the topography difference was enhanced at that stage.Besides,after the sedimentation of the grain shoal,the grainsupported framework forms under the influence of physical compaction,where the compaction rate is much lower than the finer sediments,so the depositional thickness resulted from the topography difference of various microfacies areas is also further enhanced,which shows that the grainstone thickness within a certain period of time can be used, approximately,in recovering its microtopography prominence when it began to present, and that the compaction correction can be ignored when approximately recovering the microtopography within the platform at the depositional stage.It then further analyses the effects on the grain shoal construction and reservoir development by the exposure process during the depositional stage,and it divides the shoal within the epeiric platform into three genetic types:unexposed shoal,shortmediumterm exposed shoal and longterm exposed shoal, meanwhile,pointing out that the method of grainstone grossthickness which is used,approximately,in recovering the depositional palaeogeomorphology of epeiric carbonate platform is preferable for the unexposed and shortmediumterm exposed shoals,where the main characteristics of the shortmedium term exposed shoal can be concluded as follows(contrarily be longterm exposure ):①unconformity characteristic limited,palaeosol lacks;②irregular karren and corroded fissure lack;③intargranular solution extremely develops;④the freshwater cements in early stage and cement unconformity exist;⑤lensdiagenesis reservoir of atmospheric genesis positively associates with the grainstone grossthickness.Based on this,the paper then takes the view that microtopography prominence can be inverted by the reservoir study of the grain shoal.Followed by that principle,it also suggestes that the concrete study procedure can be like this:the isochronous geologic body to be chosen as the main body of grainstone deposition,the confirmation of reservoir genesis and exposured time,the topography recovering during depositional stage and the application of achievement verification.
Sichuan Basin was characterized by developing epeiric carbonate platform during the period of Jialingjiang in early Triassic.The basin was also hit by an fierce transgression in the period of early Jia 22, which made the salinity of the seawater normal on the whole.Moxi gas field locates in the south of gentleoblique tectonic zone of the palaeohigh in the central of the basin,where the tectonic body is about 280 km2, and the exploration wells penetrating the Jia 2 member sum up to 42(data by 2005),of which the total cored wells of Jia 2 member sum up to 16,besides, the distribution is relatively uniform.Hence,the gas field was used in the case study,where the result indicates that highland mainly develop in the well areas of eastern side of Mo 24Mo 205,southern side of Mo 206,the rim of Mo 207,Mo 151Mo 36,Mo 208 and its southern part,Mo 48,Northern part of Mo 202(7 in all),which distribute in the direction of southwestnortheast,swales mainly develop in Mo 12Mo 201,Mo 0052Mo 150,southern part of Mo 22 and eastern part of Mo 206.There is thick deposition of underwatergypsum(darkgray and massive gypsum,no exposed marks found) developing in the well areas of Mo 0052Mo 150,Mo 207,which has come into being by the shoal development around the microhighland ,resulting in the sealing restrict of the lowlying environment of interbank sea and the evaporation and concentation of the waterbody,the gypsum deposition therefore comes into being.It can be believed from the above that the recovery of the palaeogeomorphology by taking advantage of the grainstone thickness can be supported by the lithofacies deposition.
According to the graph of sedimentary facies compiled by actual cored data of B Formation,Jia 22 Submember, the palaeogeomorphology during early sedimentary stage carries on developing in the stage of Jia 22B.dominating the distributing framework of its sedimentation and reservoir.The result indicates that this sort of method used in recovering the microtopography during depositional stage is applied to the characteristics of lithofacies and so on.,besides,the recovered microtopography in the sedimentary stage can not only continue to successively develop over a long period of time and can also dominate the deposition of adjacent stratigraphy and the framework of reservoir distribution,furthermore,relatively speaking,its production application effect is good,which also indicates that dedicate description of sedimentation and reservoir is an effective and adjuvant measure for those gas fields at developing stage with high density of well pattern and that this kind of method should be widely popularized,especially for those maturing basin fields with high level of well exploration,data that is out of date, rare triporosity logging series,all of these are significant and also has referenced significance for the reservoir prediction and tapping the new potential formation.
2011, 29(3): 503-511.
Abstract:
Analysis of diagenetic facies method aims at establishing the genetic link between the clastic reservoir diagenesis and the porosity evolution. The model reflecting this genetic link could provide important basis for explanation on mechanism relevant to porosity evolution and its main controls as well as vertical and horizontal distribution of favorable reservoir zone. The result of this research shows that mechanical compaction, cementation and dissolution are principal diageneses, and according to their associations, five diagenetic facies associations could be recognized as :①Early carbonate cement dissolution facies;②Weak compactionstrong dissolution facies(﹤1 800 m);③ Intermediate compactionstrong dissolution facies(1 800~2 800 m)④ Slightly strong compaction slightly strong dissolution facies(2 800~3 800 m) and ⑤ Strong compactionweak dissolution facies(﹥3 800 m). The reservoir distributed in deep water area are controlled by slightly strong compaction slightly strong dissolution facies with measured porosity ranging from 10%~20%.Type Ⅲ reservoir constitutes the major reservoir zone with some Type Ⅱand Ⅰinterlayer. Generally, Zhuhai Formation(E23zh)is dominated by slightly strong compaction slightly strong dissolution facies, and the high quality reservoirs are mainly composed of delta plain channel and beach sandstones due to porosity enhancement caused by the first secondary porosity zone. For the same reason, type Ⅲ with minor type Ⅱ and Ⅰreservoirs form the relatively favorable zone in the delta plain facies. Due to weak hydraulic dynamics and finer grain overlapped by strong compaction, type Ⅲ reservoir prevails in the delta front area.
Analysis of diagenetic facies method aims at establishing the genetic link between the clastic reservoir diagenesis and the porosity evolution. The model reflecting this genetic link could provide important basis for explanation on mechanism relevant to porosity evolution and its main controls as well as vertical and horizontal distribution of favorable reservoir zone. The result of this research shows that mechanical compaction, cementation and dissolution are principal diageneses, and according to their associations, five diagenetic facies associations could be recognized as :①Early carbonate cement dissolution facies;②Weak compactionstrong dissolution facies(﹤1 800 m);③ Intermediate compactionstrong dissolution facies(1 800~2 800 m)④ Slightly strong compaction slightly strong dissolution facies(2 800~3 800 m) and ⑤ Strong compactionweak dissolution facies(﹥3 800 m). The reservoir distributed in deep water area are controlled by slightly strong compaction slightly strong dissolution facies with measured porosity ranging from 10%~20%.Type Ⅲ reservoir constitutes the major reservoir zone with some Type Ⅱand Ⅰinterlayer. Generally, Zhuhai Formation(E23zh)is dominated by slightly strong compaction slightly strong dissolution facies, and the high quality reservoirs are mainly composed of delta plain channel and beach sandstones due to porosity enhancement caused by the first secondary porosity zone. For the same reason, type Ⅲ with minor type Ⅱ and Ⅰreservoirs form the relatively favorable zone in the delta plain facies. Due to weak hydraulic dynamics and finer grain overlapped by strong compaction, type Ⅲ reservoir prevails in the delta front area.
2011, 29(3): 520-528.
Abstract:
Nine coal samples of Jurassic Zhiluo and Yan'an Formation, collected from DongshengShenmu area of Ordos Basin, have been analysed for their proximates, ultimates and major elements. In order to discuss the influence of coalforming environmental conditions on coal properties, and study the characteristics and its control factors of major elements in coal ash of different coal accumulating systems. Ash production, mineral and organic carbon content of coal samples from different coal accumulating systems of Zhiluo and Yan'an Formation show obvious change trend. From coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation→coal seamⅤof Yan’an Formation→Zhiluo Formation, mineral content and ash production increase, organic carbon content decreases. In addition, major element contents of coal ash also have clear diversities and certain variation rules. For example, from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation →coal seamⅤof Yan’an Formation → Zhiluo Formation, SiO2 contents of coal ash samples increase; K2O contents in coal ash samples from Yan’an Formation are apparently less than those from Zhiluo Formation; besides, TFe2O3 contents of coal ash samples from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation are far more than those from coal seamⅤof Yan’an Formation and Zhiluo Formation. Based on synthetic analysis, the authors hold that the diversities of ash production, mineral content and organic carbon content of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation, are mainly controlled by coalforming environmental conditions. The degree of influence on coal by detrital material during coal forming process affects mineral content, ash production and organic carbon content of coals. However, the characteristics and diversities of coal ash major elements of different coal accumulating systems of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation are mainly controlled by the factors of coalforming environmental condition (the content of terrigenous clasts), climatic environmental condition and organic matter content.
Nine coal samples of Jurassic Zhiluo and Yan'an Formation, collected from DongshengShenmu area of Ordos Basin, have been analysed for their proximates, ultimates and major elements. In order to discuss the influence of coalforming environmental conditions on coal properties, and study the characteristics and its control factors of major elements in coal ash of different coal accumulating systems. Ash production, mineral and organic carbon content of coal samples from different coal accumulating systems of Zhiluo and Yan'an Formation show obvious change trend. From coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation→coal seamⅤof Yan’an Formation→Zhiluo Formation, mineral content and ash production increase, organic carbon content decreases. In addition, major element contents of coal ash also have clear diversities and certain variation rules. For example, from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation →coal seamⅤof Yan’an Formation → Zhiluo Formation, SiO2 contents of coal ash samples increase; K2O contents in coal ash samples from Yan’an Formation are apparently less than those from Zhiluo Formation; besides, TFe2O3 contents of coal ash samples from coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation are far more than those from coal seamⅤof Yan’an Formation and Zhiluo Formation. Based on synthetic analysis, the authors hold that the diversities of ash production, mineral content and organic carbon content of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation, are mainly controlled by coalforming environmental conditions. The degree of influence on coal by detrital material during coal forming process affects mineral content, ash production and organic carbon content of coals. However, the characteristics and diversities of coal ash major elements of different coal accumulating systems of coal seamⅡ, Ⅲ, Ⅳof Yan’an Formation, coal seamⅤof Yan’an Formation and Zhiluo Formation are mainly controlled by the factors of coalforming environmental condition (the content of terrigenous clasts), climatic environmental condition and organic matter content.
2011, 29(3): 537-543.
Abstract:
The zeolite are widely distributed in volcanic rocks of Santanghu Basin, and the main groups developed in volcanic reservoirs of CarboniferousUpper Permian strata are Haerjiawu Group, Kalagang Group, Tiaohu Group. The types of reservoir space are mostly secondary dissolution aperture, with tectoclase and unconformity dissolution secondarily. Based on the study of the rock composition statistics of the wells in the selected area, We found that volcanic rocks were mainly intermediate and basic lava, amygdala developed relatively abundant, the filling holes in almond are typically zeolitebased soluble minerals and this characteristic create the helpful conditions for the postdissolution. Ourresults have shown that the main reason of laumontite formation are hydrothermal, metasomatic alteration and volcanic materials hydration, and so on. High pH has been particularly beneficial for the formation of laumontite.
By means of observations of thin section and microscopy, combining with Xray diffraction analysis, electron microprobe analysis, We determined the type of zeolite, discussed the causes of the zeolite, and pointed out that the main type of zeolite was adelforsit, with euzeolite and analcidite secondarily, they both filled in the holes (the amygdala) and the cracks, mainly through lowtemperature volcanic hydrothermal precipitation.
The zeolite minerals occurred in the volcanic amygdala and cracks of Santanghu Basin affected the reservoir properties mainly in two aspects: the early filling of zeolite reduced the porosity and permeability conditions, and the late laumontite dissolution is the key point to improve the reservoir properties. By analyzing the relationship of zeolite content with thin section porosity, indicating that the zeolite filling in the volcanic reservoir provides material basis for the postdissolution. Laumontite dissolution is the key to the formation of secondary porosity. So, laumontite growth zone of volcanic rocks in this area should be considered. to provide a direction for exploring potential reservoir.
The zeolite are widely distributed in volcanic rocks of Santanghu Basin, and the main groups developed in volcanic reservoirs of CarboniferousUpper Permian strata are Haerjiawu Group, Kalagang Group, Tiaohu Group. The types of reservoir space are mostly secondary dissolution aperture, with tectoclase and unconformity dissolution secondarily. Based on the study of the rock composition statistics of the wells in the selected area, We found that volcanic rocks were mainly intermediate and basic lava, amygdala developed relatively abundant, the filling holes in almond are typically zeolitebased soluble minerals and this characteristic create the helpful conditions for the postdissolution. Ourresults have shown that the main reason of laumontite formation are hydrothermal, metasomatic alteration and volcanic materials hydration, and so on. High pH has been particularly beneficial for the formation of laumontite.
By means of observations of thin section and microscopy, combining with Xray diffraction analysis, electron microprobe analysis, We determined the type of zeolite, discussed the causes of the zeolite, and pointed out that the main type of zeolite was adelforsit, with euzeolite and analcidite secondarily, they both filled in the holes (the amygdala) and the cracks, mainly through lowtemperature volcanic hydrothermal precipitation.
The zeolite minerals occurred in the volcanic amygdala and cracks of Santanghu Basin affected the reservoir properties mainly in two aspects: the early filling of zeolite reduced the porosity and permeability conditions, and the late laumontite dissolution is the key point to improve the reservoir properties. By analyzing the relationship of zeolite content with thin section porosity, indicating that the zeolite filling in the volcanic reservoir provides material basis for the postdissolution. Laumontite dissolution is the key to the formation of secondary porosity. So, laumontite growth zone of volcanic rocks in this area should be considered. to provide a direction for exploring potential reservoir.
2011, 29(3): 544-551.
Abstract:
The Xrays diffraction analysis (XRD) is applied to measure the clay mineral compositions of the surface sediments in the Yangtze River drainage basin. The results show that the clay mineral compositions of the sediments display a similar pattern along the main stream, with highest content of illite and lowest content of smectite, but they are different from that in the tributary rivers, these can be responded to the heterogeneous source rocks and weathering intensity. The illite crystallity and the illite chemical weathering index (5 /10 peak ratio) of the main stream indicate a gradually increased weathering from upstream to downstream. In the tributary rivers, the lower illite chemical index in the upperreaches and the higher index in the middle and lowerreaches represent a transformation from relative dominance of physical weathering to chemical weathering. Since the upperreaches tributaries have an important influence to the whole drainage, understanding the weathering intensity does not only rely on the information of main stream, but also on that of the tributaries. Based on the result derived from the clay mineral distributions and the illite indexes, the contribution of sediments from upperreaches including the Yalong Jiang, the Dadu He, the Min Jiang and the Jialing Jiang is larger, with minor contribution from the Wu Jiang. As for the middle branches, the Han Jiang transports more sediments to the lowerreaches and the Delta, while the Xiang Jiang, Gan Jiang and the Dongting Lake contribute little.
The Xrays diffraction analysis (XRD) is applied to measure the clay mineral compositions of the surface sediments in the Yangtze River drainage basin. The results show that the clay mineral compositions of the sediments display a similar pattern along the main stream, with highest content of illite and lowest content of smectite, but they are different from that in the tributary rivers, these can be responded to the heterogeneous source rocks and weathering intensity. The illite crystallity and the illite chemical weathering index (5 /10 peak ratio) of the main stream indicate a gradually increased weathering from upstream to downstream. In the tributary rivers, the lower illite chemical index in the upperreaches and the higher index in the middle and lowerreaches represent a transformation from relative dominance of physical weathering to chemical weathering. Since the upperreaches tributaries have an important influence to the whole drainage, understanding the weathering intensity does not only rely on the information of main stream, but also on that of the tributaries. Based on the result derived from the clay mineral distributions and the illite indexes, the contribution of sediments from upperreaches including the Yalong Jiang, the Dadu He, the Min Jiang and the Jialing Jiang is larger, with minor contribution from the Wu Jiang. As for the middle branches, the Han Jiang transports more sediments to the lowerreaches and the Delta, while the Xiang Jiang, Gan Jiang and the Dongting Lake contribute little.
2011, 29(3): 561-571.
Abstract:
According to the field observation, the grain size, the element and compound analysis of 128 samples, and historical flood records of this area, we studied flood variation indicated by sediments in floodplain of the Jing River in Jingyang reach during deposit of floodplain. The result shows that the sediments which developed well on floodplain of the Jing River in Jingyang reach are mainly of coarse silt and very fine sand. Each component changes obviously in the entire profile, which can clearly reflect the variations of flood and precipitation with high resolving power. The profile is divided into 18 sediment stages, indicating 18 floods of different scales and 18 years with much precipitation. The order of depth and scale of floods of JYa from big to small is 14th, 12th, 13th, 8th, 5th, 1st, 2nd, 4th, 9th, 3rd, 7th, 6th, 11th, 10th, 18th, 15th, 16th, 17th. The flood depth of 1st is about 4.56 m, of which discharge is 4 010 m3/s. The flood depth of 14th, 12th, 13th, 8th, 5th are more than 4.56 m, of which discharge are more than 4 010 m3/s. The other flood depth are equal to or less than 4.56 m, of which discharge are equal to or less than 4 010 m3/s. The 14th flood sediment is the most thick layer of JYa, which should be the extreme flood sediment in 1841, and on the behalf of the largest flood dynamic and scale of the extreme flood event during deposit of floodplain. When the flood peak flow was 18 700 m3/s in Zhangjiashan hydrological station. The fine grain size is, the high contents of Mn,Cu,Al2O3,Fe2O3,K2O are, and the low content of Ba is, which indicates small flood intensity, low flood level and less precipitation at deposition. In contrast, The coarse grain size is, the low contents of Mn,Cu,Al2O3,Fe2O3,K2O are, and the high content of Ba is, which indicates big flood intensity, high flood level and more precipitation at deposition. The small changes of two or more elements, compounds and grain size in the thin layer was formed in the same sedimentary layer in this 18 floods indicates two or more flood peaks often appeard in the period of most floods. The sediments of 14th, 12th, 13th, 8th, 5th, 1st in floodplain of the Jing River in Jingyang reach reflect annual precipitation increase in the whole basin or largescale, and annual rainfall is more than 800 mm.
According to the field observation, the grain size, the element and compound analysis of 128 samples, and historical flood records of this area, we studied flood variation indicated by sediments in floodplain of the Jing River in Jingyang reach during deposit of floodplain. The result shows that the sediments which developed well on floodplain of the Jing River in Jingyang reach are mainly of coarse silt and very fine sand. Each component changes obviously in the entire profile, which can clearly reflect the variations of flood and precipitation with high resolving power. The profile is divided into 18 sediment stages, indicating 18 floods of different scales and 18 years with much precipitation. The order of depth and scale of floods of JYa from big to small is 14th, 12th, 13th, 8th, 5th, 1st, 2nd, 4th, 9th, 3rd, 7th, 6th, 11th, 10th, 18th, 15th, 16th, 17th. The flood depth of 1st is about 4.56 m, of which discharge is 4 010 m3/s. The flood depth of 14th, 12th, 13th, 8th, 5th are more than 4.56 m, of which discharge are more than 4 010 m3/s. The other flood depth are equal to or less than 4.56 m, of which discharge are equal to or less than 4 010 m3/s. The 14th flood sediment is the most thick layer of JYa, which should be the extreme flood sediment in 1841, and on the behalf of the largest flood dynamic and scale of the extreme flood event during deposit of floodplain. When the flood peak flow was 18 700 m3/s in Zhangjiashan hydrological station. The fine grain size is, the high contents of Mn,Cu,Al2O3,Fe2O3,K2O are, and the low content of Ba is, which indicates small flood intensity, low flood level and less precipitation at deposition. In contrast, The coarse grain size is, the low contents of Mn,Cu,Al2O3,Fe2O3,K2O are, and the high content of Ba is, which indicates big flood intensity, high flood level and more precipitation at deposition. The small changes of two or more elements, compounds and grain size in the thin layer was formed in the same sedimentary layer in this 18 floods indicates two or more flood peaks often appeard in the period of most floods. The sediments of 14th, 12th, 13th, 8th, 5th, 1st in floodplain of the Jing River in Jingyang reach reflect annual precipitation increase in the whole basin or largescale, and annual rainfall is more than 800 mm.
2011, 29(3): 587-592.
Abstract:
Through thermal simulation experiments of coal and mudstone in low mature stage(Ro=0.5%) from different sedimentary environment in one area at different temperatures（200℃,250℃,275℃,300℃,325℃,350℃,400℃,450℃）added with water in the closed system and separation and GC/MS quantitative analysis and identification of carbazole compounds in sample extracts at different temperatures, this paper discussed the distribution of carbazole compounds in this two kinds of samples at different simulation temperatures.The separation adopt twostep Column Chromatography. And absolute quantification uses Nphenylcarbazole added in neutral nitrogencontaining compounds as an internal standard . Based on simulation experiment, the article analyzes the evolutive characteristics of experimental productscarbazole compounds in nonhydrocarbon and discusses the evolution mechanism of them at different temperatures. The experimental results show that in the coal and mudstone samples the total contents of carbazole compounds and the contents of carbazoles, methyl carbazoles, dimethyl arbazoles, benzocarbazoles increase with thermal evolution temperature increasing and reach thire maximum during 325~350℃ and show downtrend after 350℃. From these changes, we can see that the formation of the compounds have certain relationship with hydrocarbon generation of rock samples.The changes with temperature of the contents of carbazole compounds depend on release and fission rate of them. The results from experimental data analysis show that contents increase when release rate is more than fission rate and contents decrease contrarily. In fact，the changes with temperature of the contents of carbazole compounds is similar to that of liquid hydrocarbons. According to the thermal simulation experiments, organic matter begin to produce hydrocarbon during 300~350℃ and reach thire maximum at about 350℃ in general. It is pointed out that nitrogencontaining compounds in geological body are the products of rockforming diagenesis of sedimentary organic matter rather than directly inherited from organism. GC/MS date of carbazole compounds indicate that the relative content of methyl carbazoles isomers changes drastically with experimental temperature.
In this two kinds of rock samples of high temperature experiments，the relative content of four methyl carbazole isomers(1 methyl carbazoles,2 methyl carbazoles,3 methyl carbazoles,4 methyl carbazoles) of methyl carbazoles present some of regular changes with temperature increasing. The content of 1methyl carbazole always predominate compared with that of the other three isomers, but the relative content of them changes drastically with temperature increasing. At 200℃, the content distribution of 2 methyl carbazoles,3 methyl carbazoles and 4 methyl carbazoles show an asymmetric “V”with forerake which become retroverted with the temperature reaching 350℃ . The relative content of dimethyl carbazoles, exposed type such as 2,6(+2,7) dimethyl carbazoles and 3,5 dimethyl carbazoles,and shielded type and half shielded type such as 1,8dimethyl carbazoles, 1,4dimethyl carbazoles and 1,5 dimethyl carbazoles, come to a head during 325～350℃and show downtrend after 350℃。In benzocarbazoles, benzo(a)carbazoles and benzo(c)carbazoles are the predominent types, benzo(b)carbazoles are few. With temperature increasing,the relative content of benzo(a)carbazoles, benzo(b)carbazoles and benzo(c)carbazoles changes drastically, reach their highest values during 325~350℃ and bagin to decrease after 350℃. It can be seen from benzocarbazole ratios(benzo(a)carbazole/(benzo(a)carbazole+benzo(c)carbazole)) that change of the ratios with temperature have good correlation with hydrocarbon generation of rock samples.But all the ratios are in the norrow range of 0.45~0.54.
Through thermal simulation experiments of coal and mudstone in low mature stage(Ro=0.5%) from different sedimentary environment in one area at different temperatures（200℃,250℃,275℃,300℃,325℃,350℃,400℃,450℃）added with water in the closed system and separation and GC/MS quantitative analysis and identification of carbazole compounds in sample extracts at different temperatures, this paper discussed the distribution of carbazole compounds in this two kinds of samples at different simulation temperatures.The separation adopt twostep Column Chromatography. And absolute quantification uses Nphenylcarbazole added in neutral nitrogencontaining compounds as an internal standard . Based on simulation experiment, the article analyzes the evolutive characteristics of experimental productscarbazole compounds in nonhydrocarbon and discusses the evolution mechanism of them at different temperatures. The experimental results show that in the coal and mudstone samples the total contents of carbazole compounds and the contents of carbazoles, methyl carbazoles, dimethyl arbazoles, benzocarbazoles increase with thermal evolution temperature increasing and reach thire maximum during 325~350℃ and show downtrend after 350℃. From these changes, we can see that the formation of the compounds have certain relationship with hydrocarbon generation of rock samples.The changes with temperature of the contents of carbazole compounds depend on release and fission rate of them. The results from experimental data analysis show that contents increase when release rate is more than fission rate and contents decrease contrarily. In fact，the changes with temperature of the contents of carbazole compounds is similar to that of liquid hydrocarbons. According to the thermal simulation experiments, organic matter begin to produce hydrocarbon during 300~350℃ and reach thire maximum at about 350℃ in general. It is pointed out that nitrogencontaining compounds in geological body are the products of rockforming diagenesis of sedimentary organic matter rather than directly inherited from organism. GC/MS date of carbazole compounds indicate that the relative content of methyl carbazoles isomers changes drastically with experimental temperature.
In this two kinds of rock samples of high temperature experiments，the relative content of four methyl carbazole isomers(1 methyl carbazoles,2 methyl carbazoles,3 methyl carbazoles,4 methyl carbazoles) of methyl carbazoles present some of regular changes with temperature increasing. The content of 1methyl carbazole always predominate compared with that of the other three isomers, but the relative content of them changes drastically with temperature increasing. At 200℃, the content distribution of 2 methyl carbazoles,3 methyl carbazoles and 4 methyl carbazoles show an asymmetric “V”with forerake which become retroverted with the temperature reaching 350℃ . The relative content of dimethyl carbazoles, exposed type such as 2,6(+2,7) dimethyl carbazoles and 3,5 dimethyl carbazoles,and shielded type and half shielded type such as 1,8dimethyl carbazoles, 1,4dimethyl carbazoles and 1,5 dimethyl carbazoles, come to a head during 325～350℃and show downtrend after 350℃。In benzocarbazoles, benzo(a)carbazoles and benzo(c)carbazoles are the predominent types, benzo(b)carbazoles are few. With temperature increasing,the relative content of benzo(a)carbazoles, benzo(b)carbazoles and benzo(c)carbazoles changes drastically, reach their highest values during 325~350℃ and bagin to decrease after 350℃. It can be seen from benzocarbazole ratios(benzo(a)carbazole/(benzo(a)carbazole+benzo(c)carbazole)) that change of the ratios with temperature have good correlation with hydrocarbon generation of rock samples.But all the ratios are in the norrow range of 0.45~0.54.
2011, 29(3): 599-604.
Abstract:
According to source control theory, most reservoirs lie in ambient region of source rock. The kernel content of "Source Control Theory" is that oil & gas migration distance is short. Most of them distribute between 20 km and 30 km.The west slope in the Songliao basin is outside of source rock distribution. However, several oilfield have been found in the west slope, such as Fulaerji, Pingyang ,Taobao, Tumuji and so on. A large channel is found in the west slope and this research shows that this channel control distribution of Baicheng & Honggang river system. The channel and its river system is the most effective migration way for the reservoirs in the west slope. The wells in this channel all have good signs oil migration. The regional cap formed by the lacustrine shale in Nen Ⅰ and Ⅱ members, sandstone of high porosity and high permeability in the channel, and single slanted slope provide the geologic conditions for the hydrocarbon generated in Changelin Sag to migrate towards the west slope the channel and its river is a kind of expressway of hydrocarbon migration. Therefore, it is possible that explorer may seek reservoirs alone expressway beyond the region of source rock.
According to source control theory, most reservoirs lie in ambient region of source rock. The kernel content of "Source Control Theory" is that oil & gas migration distance is short. Most of them distribute between 20 km and 30 km.The west slope in the Songliao basin is outside of source rock distribution. However, several oilfield have been found in the west slope, such as Fulaerji, Pingyang ,Taobao, Tumuji and so on. A large channel is found in the west slope and this research shows that this channel control distribution of Baicheng & Honggang river system. The channel and its river system is the most effective migration way for the reservoirs in the west slope. The wells in this channel all have good signs oil migration. The regional cap formed by the lacustrine shale in Nen Ⅰ and Ⅱ members, sandstone of high porosity and high permeability in the channel, and single slanted slope provide the geologic conditions for the hydrocarbon generated in Changelin Sag to migrate towards the west slope the channel and its river is a kind of expressway of hydrocarbon migration. Therefore, it is possible that explorer may seek reservoirs alone expressway beyond the region of source rock.
