2004 Vol. 22, No. 1
column
Display Method:
2004, 22(1): 1-5.
Abstract:
According to the principle of strontium isotope stratigraphy (SIS), we establish the Ordovician data baseof 87 Sr/ 86 Sr ratio through the geological timefrom the digitized global marine strontium isotope curve. We have confirmed the boundaries of middle upper and middle lower Ordovicianusing the analytic data of strontium isotope of the Well Tazhong 12 in Tarim basin.The two boundaries are located atthe depth of 5 120 m ( 87 Sr/ 86 Sr≈ 0.708 8,with theage of 465 Ma)and4 880 m( 87 Sr/ 86 Sr≈ 0.708 2,with theage of 455 Ma),respectively, of the Well Tazhong 12. The verificationof middle upper Ordovicianboundary is just the first time for this well,and the location of the boundary of middle lower Ordovician confirmed is consistent with the depth of middle upper Ordovician boundary calibratedby conodontdata.This variation of strontium isotope curve for the Well Tazhong 12 shows the following facts: despite the tectonic movementresulted in the rising of Tarim basin, leading to the leaching of meteoricwater to the upper most part of Ordoviciancarbonate, and to the increase of 87 Sr/ 86 Sr of some samples, the relationship between Ordovicianand its upper strata of the Well Tazhong 12 is transitionary. The top boundary for Ordovicianis located at the depth of 4 650 m ( 87 Sr/ 86 Sr≈ 0.707 9,with theage of 435 Ma).
According to the principle of strontium isotope stratigraphy (SIS), we establish the Ordovician data baseof 87 Sr/ 86 Sr ratio through the geological timefrom the digitized global marine strontium isotope curve. We have confirmed the boundaries of middle upper and middle lower Ordovicianusing the analytic data of strontium isotope of the Well Tazhong 12 in Tarim basin.The two boundaries are located atthe depth of 5 120 m ( 87 Sr/ 86 Sr≈ 0.708 8,with theage of 465 Ma)and4 880 m( 87 Sr/ 86 Sr≈ 0.708 2,with theage of 455 Ma),respectively, of the Well Tazhong 12. The verificationof middle upper Ordovicianboundary is just the first time for this well,and the location of the boundary of middle lower Ordovician confirmed is consistent with the depth of middle upper Ordovician boundary calibratedby conodontdata.This variation of strontium isotope curve for the Well Tazhong 12 shows the following facts: despite the tectonic movementresulted in the rising of Tarim basin, leading to the leaching of meteoricwater to the upper most part of Ordoviciancarbonate, and to the increase of 87 Sr/ 86 Sr of some samples, the relationship between Ordovicianand its upper strata of the Well Tazhong 12 is transitionary. The top boundary for Ordovicianis located at the depth of 4 650 m ( 87 Sr/ 86 Sr≈ 0.707 9,with theage of 435 Ma).
2004, 22(1): 13-18.
Abstract:
Large amount of data are used to analyze the role of low permeability reservoir in petroleum explorationof China. There is no doubt that low permeability reservoir is the main field of petroleum exploration at present andin future whether in East China or West China. So we must pay full attention to the study on it.The characteris-tics of low permeability reservoir are summed up in the paper. They are thin sediment,low textural maturity andcompositional maturity,bad reservoir properties,low porosity and permeability,small pore throat size,great dif-ference of diagenesis,intense stress sensibility,developed fractures and strong heterogeneity. In view of thosecharacteristics,the authors analyze the mechanism of low permeability reservoir and think that sedimentary envi-ronment is the main cause,especially for the strata bearing coal near planation surface. In addition,diagenesis andtectonism are two of the main factors. The paper will play certain guidance and reference roles in the explorationand development of low permeability reservoir in the future.
Large amount of data are used to analyze the role of low permeability reservoir in petroleum explorationof China. There is no doubt that low permeability reservoir is the main field of petroleum exploration at present andin future whether in East China or West China. So we must pay full attention to the study on it.The characteris-tics of low permeability reservoir are summed up in the paper. They are thin sediment,low textural maturity andcompositional maturity,bad reservoir properties,low porosity and permeability,small pore throat size,great dif-ference of diagenesis,intense stress sensibility,developed fractures and strong heterogeneity. In view of thosecharacteristics,the authors analyze the mechanism of low permeability reservoir and think that sedimentary envi-ronment is the main cause,especially for the strata bearing coal near planation surface. In addition,diagenesis andtectonism are two of the main factors. The paper will play certain guidance and reference roles in the explorationand development of low permeability reservoir in the future.
2004, 22(1): 29-35.
Abstract:
Taking North Jiangsu basin as an example, this paperdemonstratesthe characteristicsof clay minerals assemblagesand the controlling factors in igneous regionssystemically, establishes the patterns of diagenetic transformation, analysespalaeo temperature according to the evolutionary features of the clay minerals. The distribution of clay minerals ismainly influenced by burial diagenesis, magma intrusion, volcanic clastic rocksandthere are fourtypes of clay mineral assemblages in North Jiangsu basin. The clay mineral assemblagesof smectite randomI/S and randomI/S illiteoccurin early diagenetic stagewith a vitrinite reflectance value of less than 0.55%, the assemblageof illite ordered I/S occursin middle diagenetic stagewith a vitrinite reflectance value of more than 0.55%,the assemblageof kaoliniteordered I/Soccursin middle and late diagenetic stage with a vitrinite reflectance value of more than 1.0%. There are special clay minerals assemblagesand diagenetic evolution models in regions of volcanic clastic rocks and magma intrusion. As the present of volcanogenic detrital materialregions, the assemblage of smectite randomI/S occurs repeatedly in vertical with the content of smectite of more than 90% in Fu'an region of Hai'an depression. Its evolution model is the assemblages from smectite randomI/S, to randomI/S illite, to Smectite randomI/S, to randomI/S illite, and illite ordered I/S. Gaoyou depression,being a represenative of magma intrusion regions, has a discontinuous evoluting sequence of the assemblages from smectite randomI/S,to randomI/S-illite, and kaolinite-ordered I/S, where kaoliniteand ordered I/S are observed coexisting. The evolution model of clay mineral in other regions is the assemblages from smectite randomI/S,to randomI/S illite, to illite ordered I/S. Short distance ordered I/S occurs at a vitrinite reflectance value of 0.5%～0.55%, the transformation from ordered I/Sto illite occurs at 3 280～3 390m in depth and 137 o C in temperature. The transforming surface can be used to estimate maturityand palaeo temperature while the disappearing surface of smectite can not be thermal indicator.
Taking North Jiangsu basin as an example, this paperdemonstratesthe characteristicsof clay minerals assemblagesand the controlling factors in igneous regionssystemically, establishes the patterns of diagenetic transformation, analysespalaeo temperature according to the evolutionary features of the clay minerals. The distribution of clay minerals ismainly influenced by burial diagenesis, magma intrusion, volcanic clastic rocksandthere are fourtypes of clay mineral assemblages in North Jiangsu basin. The clay mineral assemblagesof smectite randomI/S and randomI/S illiteoccurin early diagenetic stagewith a vitrinite reflectance value of less than 0.55%, the assemblageof illite ordered I/S occursin middle diagenetic stagewith a vitrinite reflectance value of more than 0.55%,the assemblageof kaoliniteordered I/Soccursin middle and late diagenetic stage with a vitrinite reflectance value of more than 1.0%. There are special clay minerals assemblagesand diagenetic evolution models in regions of volcanic clastic rocks and magma intrusion. As the present of volcanogenic detrital materialregions, the assemblage of smectite randomI/S occurs repeatedly in vertical with the content of smectite of more than 90% in Fu'an region of Hai'an depression. Its evolution model is the assemblages from smectite randomI/S, to randomI/S illite, to Smectite randomI/S, to randomI/S illite, and illite ordered I/S. Gaoyou depression,being a represenative of magma intrusion regions, has a discontinuous evoluting sequence of the assemblages from smectite randomI/S,to randomI/S-illite, and kaolinite-ordered I/S, where kaoliniteand ordered I/S are observed coexisting. The evolution model of clay mineral in other regions is the assemblages from smectite randomI/S,to randomI/S illite, to illite ordered I/S. Short distance ordered I/S occurs at a vitrinite reflectance value of 0.5%～0.55%, the transformation from ordered I/Sto illite occurs at 3 280～3 390m in depth and 137 o C in temperature. The transforming surface can be used to estimate maturityand palaeo temperature while the disappearing surface of smectite can not be thermal indicator.
2004, 22(1): 41-46.
Abstract:
This paper discussed the sedimentary property, vertical sequence and geological significance of seismites of Paleogene in Huimin sag, Shandong Province. Seismite is a kind of catastrophic event rock, being the terrane with ancient earthquake records. Huimin sag was a fault lake in Paleogenein Bohaiwan basin. The sandstones and mudstones were the main sedimentary rocks with in the sag. Many typical deformation structures were caused by widespread earthquake in the sag. They were syn sedimentary microfactures (includingfault graded), seismic fissure bed, sandstone vein, water escape structure, "pillow structure", ball structure, convolute lamination, load structure and flame structure, etc. The vertical sequence of seismite of petroclastic rock in Paleogene in Huimin sag, from bottom to top, included 6 units: underlying unshocked layer, fissure layer, microfold layer, pillow structure and partner structure layer, liquefied homogeneous layer and overlying unshocked layer. Thecompletenessof the vertical sequence dependsonthe location of section, seismic level, especially the lithology. It is of important geologicalsignificance to study seismite. Most seismites in Paleogene in Huimin sag developed near the peripheral faults and central fault zone of the sag. The mass appearanceof seismites reflected the intensively active period of basin-controlling boundary faults, andcan be used to interpret the tectonic evolvement of fault basin. The seismites in fault basin can be likely reservoir for their specialtectonic location and structures.
This paper discussed the sedimentary property, vertical sequence and geological significance of seismites of Paleogene in Huimin sag, Shandong Province. Seismite is a kind of catastrophic event rock, being the terrane with ancient earthquake records. Huimin sag was a fault lake in Paleogenein Bohaiwan basin. The sandstones and mudstones were the main sedimentary rocks with in the sag. Many typical deformation structures were caused by widespread earthquake in the sag. They were syn sedimentary microfactures (includingfault graded), seismic fissure bed, sandstone vein, water escape structure, "pillow structure", ball structure, convolute lamination, load structure and flame structure, etc. The vertical sequence of seismite of petroclastic rock in Paleogene in Huimin sag, from bottom to top, included 6 units: underlying unshocked layer, fissure layer, microfold layer, pillow structure and partner structure layer, liquefied homogeneous layer and overlying unshocked layer. Thecompletenessof the vertical sequence dependsonthe location of section, seismic level, especially the lithology. It is of important geologicalsignificance to study seismite. Most seismites in Paleogene in Huimin sag developed near the peripheral faults and central fault zone of the sag. The mass appearanceof seismites reflected the intensively active period of basin-controlling boundary faults, andcan be used to interpret the tectonic evolvement of fault basin. The seismites in fault basin can be likely reservoir for their specialtectonic location and structures.
2004, 22(1): 59-66.
Abstract:
Black rock series at the bottom of the Lower Cambrian in the Northern Tarim Basin, China, is com 2posed of black shales interbedded with thin - bedded cherts. Six chert samples were systematically collected from avertical section of 8. 8 meters in depth in Xiaoerbulak, Northern Tarim Basin. The cherts were crushed and ana 2lyzed for trace element and rare earth concentrations. Trace elements such as V, Cu, Zn, U, Pb, Ba, Cd, Ag,Mo, As and Sb are highly enriched, and others such as Rb, Zr, Cs, Hf, Ta, W, Tl, Bi and Th are highly deplet 2ed in the cherts. These trace element patterns suggest that the cherts may be of deep crustal origin. The low ratiosof Th/ U and Rb/ Sr further suggest that the cherts are of earth interior sourcesor received hydrothermal input dur 2ing their deposition. The chondrite - normalized Ce/ Ce3ratio rangesfrom 0. 42 to 0. 83, with an average of 0. 60.North American Shale Composite (NASC) - normalized Ce/ Ce3ratio ranges from 0. 42 to 0. 79, with an averageof 0. 57. Negative Ce anomalies are distinct. ∑ REEs in the cherts generally increase from 10. 50 ppm at the bot 2tom to 35. 97 ppm at the top of the sampled section. NASC - normalized (La/ Lu) N ratio decreases from 2. 72 atthe bottom to 0. 67 at the top. NASC - normalized (La/ Ce) N ratio increases from 1. 36 at the bottom to 3. 13 atthe top. These REE patterns are very similar to those for the cherts deposited in the pelagic ocean - basin floor inthe Franciscan Complex exposed at Marin Headlands, California (F - MH chert) (Murray et al.,1991). Chon 2drite - normalized Eu/ Eu3value markedly decreases upward in the section from 5. 54 at the lowermost to 0. 73 atthe top, and NASC - normalized Eu/ Eu3value decreasesfrom 8. 05 to 1. 03. The relatively high Eu/ Eu3ratio forthe chertsfrom the North Tarim Basin is most likely due to a hydrothermal input (e. g., Eu/ Eu3 ～10). The sys 2tematic decrease of Eu/ Eu3ratio from the bottom to the top of the section reflects that the hydrothermal input isthe largest in the lowermost portion of the section and gradually decreases upward. These geochemical characteris 2tics indicate that the cherts from the bottom of the Lower Cambrian in the Northern Tarim Basin should be de 2posited on a pelagic ocean - basin floor in proximity to the mid ocean ridge that provided much interior source/ hy 2drothermal input, but this conclusion is in quite contradiction to that from the sedimentological research. On thebasis of the comprehensive studiesof regional geology and geochemistry of black shales, it is considered that the up 2welling carries the substances formed in the pelagic ocean floor onto shelf to deposit, which results in the pelagicgeochmical characteristics of the bedded cherts deposited on shelf.
Black rock series at the bottom of the Lower Cambrian in the Northern Tarim Basin, China, is com 2posed of black shales interbedded with thin - bedded cherts. Six chert samples were systematically collected from avertical section of 8. 8 meters in depth in Xiaoerbulak, Northern Tarim Basin. The cherts were crushed and ana 2lyzed for trace element and rare earth concentrations. Trace elements such as V, Cu, Zn, U, Pb, Ba, Cd, Ag,Mo, As and Sb are highly enriched, and others such as Rb, Zr, Cs, Hf, Ta, W, Tl, Bi and Th are highly deplet 2ed in the cherts. These trace element patterns suggest that the cherts may be of deep crustal origin. The low ratiosof Th/ U and Rb/ Sr further suggest that the cherts are of earth interior sourcesor received hydrothermal input dur 2ing their deposition. The chondrite - normalized Ce/ Ce3ratio rangesfrom 0. 42 to 0. 83, with an average of 0. 60.North American Shale Composite (NASC) - normalized Ce/ Ce3ratio ranges from 0. 42 to 0. 79, with an averageof 0. 57. Negative Ce anomalies are distinct. ∑ REEs in the cherts generally increase from 10. 50 ppm at the bot 2tom to 35. 97 ppm at the top of the sampled section. NASC - normalized (La/ Lu) N ratio decreases from 2. 72 atthe bottom to 0. 67 at the top. NASC - normalized (La/ Ce) N ratio increases from 1. 36 at the bottom to 3. 13 atthe top. These REE patterns are very similar to those for the cherts deposited in the pelagic ocean - basin floor inthe Franciscan Complex exposed at Marin Headlands, California (F - MH chert) (Murray et al.,1991). Chon 2drite - normalized Eu/ Eu3value markedly decreases upward in the section from 5. 54 at the lowermost to 0. 73 atthe top, and NASC - normalized Eu/ Eu3value decreasesfrom 8. 05 to 1. 03. The relatively high Eu/ Eu3ratio forthe chertsfrom the North Tarim Basin is most likely due to a hydrothermal input (e. g., Eu/ Eu3 ～10). The sys 2tematic decrease of Eu/ Eu3ratio from the bottom to the top of the section reflects that the hydrothermal input isthe largest in the lowermost portion of the section and gradually decreases upward. These geochemical characteris 2tics indicate that the cherts from the bottom of the Lower Cambrian in the Northern Tarim Basin should be de 2posited on a pelagic ocean - basin floor in proximity to the mid ocean ridge that provided much interior source/ hy 2drothermal input, but this conclusion is in quite contradiction to that from the sedimentological research. On thebasis of the comprehensive studiesof regional geology and geochemistry of black shales, it is considered that the up 2welling carries the substances formed in the pelagic ocean floor onto shelf to deposit, which results in the pelagicgeochmical characteristics of the bedded cherts deposited on shelf.
2004, 22(1): 73-78.
Abstract:
By using short term base level cycle theory of high resolution sequence stratigraphy, we delicately analyzed reservoir sandstones which deposited on the delta front gentle slope zone with Chang Ⅲ oil Formation in Chenghua area, Shanxi gansu ningxia basin. On the base of genetic, reservoir sandstones may be divided into three types of sandstones that consist of six subtypes. While these sandstones genetic are evidently influenced by the short term base level up and down changes and the relation of accompanied accommodations and sediment alimentations. In the course of base level rising, ① A/S1, sandstone genetic type is mainly truncated distributary channel sandstone body. ② A/S1, sandstone genetic type is mainly integrated distributary channel sandstone body. There is recombination bar genetic sandstone body at the underwater slope break zone. With the base level up and down changes, regular change of short term base level cycle influences the distribution of different genetic sandstone bodies. And distributional model of different genetic sandstones that deposit on different locals of delta front at gentle slope in depressed type lacustrine basin is built.
By using short term base level cycle theory of high resolution sequence stratigraphy, we delicately analyzed reservoir sandstones which deposited on the delta front gentle slope zone with Chang Ⅲ oil Formation in Chenghua area, Shanxi gansu ningxia basin. On the base of genetic, reservoir sandstones may be divided into three types of sandstones that consist of six subtypes. While these sandstones genetic are evidently influenced by the short term base level up and down changes and the relation of accompanied accommodations and sediment alimentations. In the course of base level rising, ① A/S1, sandstone genetic type is mainly truncated distributary channel sandstone body. ② A/S1, sandstone genetic type is mainly integrated distributary channel sandstone body. There is recombination bar genetic sandstone body at the underwater slope break zone. With the base level up and down changes, regular change of short term base level cycle influences the distribution of different genetic sandstone bodies. And distributional model of different genetic sandstones that deposit on different locals of delta front at gentle slope in depressed type lacustrine basin is built.
2004, 22(1): 87-94.
Abstract:
In this paper, the author integratesthe controllingfactors of sequence with sedimentary response. It takes a short term base level cycleas a geneticstratigraphic unit to discuss the different accommodationspace development, the change of fluvial process, macroscopic distribution of reservoirs, the influence of sediment supply in a down warped basin or a rift basin where shallow water braided delta develops. Taking the Tabamiao Area of Ordos Basin and the Baobei Block, Baolang Oil field of Yanqi Basin as examples, It points out some identification symbols such as the wash plane and incised valley at the bottom of thick overlap sand-body, the meandering of braided distributary channel, the sedimentaries of offshore barrier faciesand offshore marsh facies. It provides the theoretical evidence for stable and thick coal bed regarded as a mark of formation comparison. The conception, overplus subaerial accommodationspace, explains reasonablywhy the reservoirs mainly distributein rise half cycle of base levelcycle.
In this paper, the author integratesthe controllingfactors of sequence with sedimentary response. It takes a short term base level cycleas a geneticstratigraphic unit to discuss the different accommodationspace development, the change of fluvial process, macroscopic distribution of reservoirs, the influence of sediment supply in a down warped basin or a rift basin where shallow water braided delta develops. Taking the Tabamiao Area of Ordos Basin and the Baobei Block, Baolang Oil field of Yanqi Basin as examples, It points out some identification symbols such as the wash plane and incised valley at the bottom of thick overlap sand-body, the meandering of braided distributary channel, the sedimentaries of offshore barrier faciesand offshore marsh facies. It provides the theoretical evidence for stable and thick coal bed regarded as a mark of formation comparison. The conception, overplus subaerial accommodationspace, explains reasonablywhy the reservoirs mainly distributein rise half cycle of base levelcycle.
2004, 22(1): 103-109.
Abstract:
Tazhong area is located in the middle of Tarim Basin, which is a major oil production area of Tarim Oil field. The carbonate of Ordovician is one of the most important target strata for oil exploration. Guided with the theory of high resolution sequence stratigraphy and based on the data of outcrop sections, well logs and rock core, the primary research of sequence stratigrphy is conducted, and the interfaces of third order sequences of middle upper Ordivician in this area identified. Combined with the analysis of slices and by using characteristic diagenesis fabric to identify indications of meteorite water diagenesis, 4 meteoric water diagenetic lenses are identified, and outcrop sections of sequence and meteoric water diagenetic lenses are constructed, by which sequence interfaces of different levels made on carbonate iyngenesis karst at the edge of mesas, is of importantly instructive meaning to exactly forecast the development order of carbonate reservoir.
Tazhong area is located in the middle of Tarim Basin, which is a major oil production area of Tarim Oil field. The carbonate of Ordovician is one of the most important target strata for oil exploration. Guided with the theory of high resolution sequence stratigraphy and based on the data of outcrop sections, well logs and rock core, the primary research of sequence stratigrphy is conducted, and the interfaces of third order sequences of middle upper Ordivician in this area identified. Combined with the analysis of slices and by using characteristic diagenesis fabric to identify indications of meteorite water diagenesis, 4 meteoric water diagenetic lenses are identified, and outcrop sections of sequence and meteoric water diagenetic lenses are constructed, by which sequence interfaces of different levels made on carbonate iyngenesis karst at the edge of mesas, is of importantly instructive meaning to exactly forecast the development order of carbonate reservoir.
2004, 22(1): 124-129.
Abstract:
Sediment parameters of inter tidal flat are related to the depositional hydrodynamic conditions associated with the local sedimentary environment. During July August, 2000, 154 surface sediment samples were collected on the intertidal flat of Wanggang. The sediment samples are then analyzed using Mastersize2000. Further, the regression analysis shows that the significant relationships are present between the sediment parameters, and as well with ( M z Φ M d Φ). In addition, the grain size diameters decrease landward with the decreasing of the hydrodynamics. Five types of sediments have been identified for the Wanggang intertidal flat:fine sand, silty sand, sandy silt, silt and clayey silt. In brief, there are two main sediment types, i.e. silt and sand with the percentages of 57.8% and 42.2% respectively. These results differ from other intertidal flats associated with different sediment sources, hydrodynamic environments and bio influences. The results of grain size trends show that the sediments mainly transport northwestward near the sub tidal zone; but southward, southwestward and southeastward, which are related to tide regimes, local landscape, large human constructions and the biological activities.
Sediment parameters of inter tidal flat are related to the depositional hydrodynamic conditions associated with the local sedimentary environment. During July August, 2000, 154 surface sediment samples were collected on the intertidal flat of Wanggang. The sediment samples are then analyzed using Mastersize2000. Further, the regression analysis shows that the significant relationships are present between the sediment parameters, and as well with ( M z Φ M d Φ). In addition, the grain size diameters decrease landward with the decreasing of the hydrodynamics. Five types of sediments have been identified for the Wanggang intertidal flat:fine sand, silty sand, sandy silt, silt and clayey silt. In brief, there are two main sediment types, i.e. silt and sand with the percentages of 57.8% and 42.2% respectively. These results differ from other intertidal flats associated with different sediment sources, hydrodynamic environments and bio influences. The results of grain size trends show that the sediments mainly transport northwestward near the sub tidal zone; but southward, southwestward and southeastward, which are related to tide regimes, local landscape, large human constructions and the biological activities.
2004, 22(1): 136-141.
Abstract:
Outangdi Formation in Jiangshan, Zhejiang is the mixing deposits of terrigenous clastics and carbonatein Weiningian of late 2 Carboniferous. The mixing deposits include the interbedding which constitutes a series of in 2terbedded clastic beds and carbonate beds and the mixing within in the same bed which forms the ” Hunji rock ”.Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational se 2quences with lower fine and upper coarse of sedimentary granularity in the section. Hunji rock isformed in seashoreenvironment, mixed carbonate sediment in beach or tideland facies with quartz sand taken from bayou or beach bycoastwise flow and circumfluence. There are two kinds of Hunji sequences: interbeds of sandstone and carbonaterock in seashore environment, interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicatedthat mixing deposition belong to ” facies mixing ”, affected mainly by regional toctonic uplift, rise of global sea leveland dynamics of water medium in the basin. Regional sea level periodic change and progradational sequences wereprobably due to intense uplift of the oldland called Cathaysia. The classification and name of mixed sediments arealso discussed in this paper. Interbeds and alternated beds of clastic and carbonate beds are named as ” hunji se 2quence ”, a new genetic term. It is suggested that Hunji rock means a special sedimentary event of mixing of ter 2rigenous clastics and carbonate instead of a term of specific rock.
Outangdi Formation in Jiangshan, Zhejiang is the mixing deposits of terrigenous clastics and carbonatein Weiningian of late 2 Carboniferous. The mixing deposits include the interbedding which constitutes a series of in 2terbedded clastic beds and carbonate beds and the mixing within in the same bed which forms the ” Hunji rock ”.Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational se 2quences with lower fine and upper coarse of sedimentary granularity in the section. Hunji rock isformed in seashoreenvironment, mixed carbonate sediment in beach or tideland facies with quartz sand taken from bayou or beach bycoastwise flow and circumfluence. There are two kinds of Hunji sequences: interbeds of sandstone and carbonaterock in seashore environment, interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicatedthat mixing deposition belong to ” facies mixing ”, affected mainly by regional toctonic uplift, rise of global sea leveland dynamics of water medium in the basin. Regional sea level periodic change and progradational sequences wereprobably due to intense uplift of the oldland called Cathaysia. The classification and name of mixed sediments arealso discussed in this paper. Interbeds and alternated beds of clastic and carbonate beds are named as ” hunji se 2quence ”, a new genetic term. It is suggested that Hunji rock means a special sedimentary event of mixing of ter 2rigenous clastics and carbonate instead of a term of specific rock.
2004, 22(1): 148-153.
Abstract:
Thesynsedimentary fault in coal accumulating basin had a clear controlling role in the thickness, lithofacies and coal bearing nature of coal bearing series, and not only became a geological natural boundary but also had a direct effect on design of mining area and coal production because of its inheritable mobility after coal forming period.More recently,it is discovered that Hutoushan fault in Yuzhou coalfield is a large syndepositional inherited coal controlling structure. It was active during coal forming period. Based on the lithology,sedimentary thickness,coal accumulation,stratigraphic throw, disharmonic sedimentation at side of fault zone and result of trend surface analysis, it was proven to be a syndepositional fault in coal forming period. And after coal forming period posthumous movement took place again, with the evidences of bedrock dislocation and stratigraphic lacuna, control and reformation of landform and Cenozoicsedimentation, development of second order structures and traction of cool outcropping and features of fracture crushed zone,and so on. This discovery is very important and valuable both in theory and in practice, which gives guide lines for construction of mine,production,studying coalbed thickness,tectonics of Yuzhou coalfield and tectonicevolution of the north China plate.
Thesynsedimentary fault in coal accumulating basin had a clear controlling role in the thickness, lithofacies and coal bearing nature of coal bearing series, and not only became a geological natural boundary but also had a direct effect on design of mining area and coal production because of its inheritable mobility after coal forming period.More recently,it is discovered that Hutoushan fault in Yuzhou coalfield is a large syndepositional inherited coal controlling structure. It was active during coal forming period. Based on the lithology,sedimentary thickness,coal accumulation,stratigraphic throw, disharmonic sedimentation at side of fault zone and result of trend surface analysis, it was proven to be a syndepositional fault in coal forming period. And after coal forming period posthumous movement took place again, with the evidences of bedrock dislocation and stratigraphic lacuna, control and reformation of landform and Cenozoicsedimentation, development of second order structures and traction of cool outcropping and features of fracture crushed zone,and so on. This discovery is very important and valuable both in theory and in practice, which gives guide lines for construction of mine,production,studying coalbed thickness,tectonics of Yuzhou coalfield and tectonicevolution of the north China plate.
2004, 22(1): 161-168.
Abstract:
It was suggested that 2 600 m is the boundary of early and later stage of diagenesis in Niuzhuang South Slope, Dongyi Depression, Bohai Bay Basin according to porosity, illite/montmorillonite ratio and acoustic transit time, and no abnormal formation pressure was observed from Es4 intervals located in the Niuzhuang South Slope. It was proved that 2 700 m is oil generation threshold (Ro=0.5%) of normal oil window based on vitrinite reflectance and thermal evaluation of biomarkers as well as oil source rock correlation results previously. No solid proofs support the opinion that Es4 shales located in the Niuzhuang South Slope should be the main source rock of oil pools in Bamihe oilfield. It was assumed that less mature oils with small amount as suggested by our recent reinvestigation were expelled through faults, shale layer under formation pressure of overlying intervals periodically. Particularly, deeper fluid pressure was suggested to play active roles in hydrocarbons expulsion of shall intervals indirectly, which is created by large amount of generated and expelled hydrocarbons. Hydrocarbons generated by source rocks with wide range of thermal maturity were expelled by abnormal fluid pressure periodically and contemporaneously leading to mixing of the oils with different maturity during primary migration. Relative small amount of hydrocarbons generated and low efficiency of hydrocarbons expulsion are responsible for low immature petroleum resource of Bamihe oilfield.
It was suggested that 2 600 m is the boundary of early and later stage of diagenesis in Niuzhuang South Slope, Dongyi Depression, Bohai Bay Basin according to porosity, illite/montmorillonite ratio and acoustic transit time, and no abnormal formation pressure was observed from Es4 intervals located in the Niuzhuang South Slope. It was proved that 2 700 m is oil generation threshold (Ro=0.5%) of normal oil window based on vitrinite reflectance and thermal evaluation of biomarkers as well as oil source rock correlation results previously. No solid proofs support the opinion that Es4 shales located in the Niuzhuang South Slope should be the main source rock of oil pools in Bamihe oilfield. It was assumed that less mature oils with small amount as suggested by our recent reinvestigation were expelled through faults, shale layer under formation pressure of overlying intervals periodically. Particularly, deeper fluid pressure was suggested to play active roles in hydrocarbons expulsion of shall intervals indirectly, which is created by large amount of generated and expelled hydrocarbons. Hydrocarbons generated by source rocks with wide range of thermal maturity were expelled by abnormal fluid pressure periodically and contemporaneously leading to mixing of the oils with different maturity during primary migration. Relative small amount of hydrocarbons generated and low efficiency of hydrocarbons expulsion are responsible for low immature petroleum resource of Bamihe oilfield.
2004, 22(1): 176-181.
Abstract:
It is very important to study the mantle fluids for understanding deep geologic processes within the earth. There are following rules for degassing of mantle fluids by step-heating for the mantle xenoliths of Shandong province: ①the degassing characters of primary mantle fluid components are different and they are: the degassing peak value for CH 4 are always at 500℃, and while more H2 were degassed with higher temperature as less CO2 were released;②three type fluids degassed in different temperature stage, such as 350～500℃,650～800℃ and 950～1100℃, implying different evolving stage fluids, were recognized.
It is very important to study the mantle fluids for understanding deep geologic processes within the earth. There are following rules for degassing of mantle fluids by step-heating for the mantle xenoliths of Shandong province: ①the degassing characters of primary mantle fluid components are different and they are: the degassing peak value for CH 4 are always at 500℃, and while more H2 were degassed with higher temperature as less CO2 were released;②three type fluids degassed in different temperature stage, such as 350～500℃,650～800℃ and 950～1100℃, implying different evolving stage fluids, were recognized.
2004, 22(1): 6-12.
Abstract:
In order to elucidate origin and pattern of cement calcites filled in fissure and cave,thirty-one calcite ce-ment samples collected in cavity and fissure in Ordovician carbonate of Tahe oilfield,Xmjiang were geochemicallyanalyzed,and the factor analysis and cluster analysis methods are used in such a large quantity of analytical data,the results show that:1.alcite cements are pure with the average mol%contents of CaCO3,MgCO3,FeCO3 andMnCO3 equal to 98.38,0. 87,0. 68 and 0. 07,respectively,and average content of SiO2,A12O3 equal to 1.95%and0. 73%,and Sr,BaO contain 131.4 X10-6 and 516. 5 X10-6 as well as F and C1 equal to 0. 014%and in 0. 013%,and the average ratio of (Mn+Fe)/Mg and Mn/ Fe equal 0. 87 and 0. 10,moreover,a linear covariance of Sr andMg concentrations of calcites expressed by the following relationship:Sr/ Ca=0. 00618Mg/ Ca+0.000533(Rz=0. 197),which indicates the abiotic origin of calcites;The six principle component consist of the major and traceelements with a certain of significant indication sedimentation factors and diagenetic environments;all of thesamples can be divided into four groups in cluster analysis,among them,the first group represented by S67-W 037and others document the characteristic of meteoric flushing product in phreatic wne and apparently undergone a se-ries of strong waterrock reactions or burial diagenetic reactions;the second group represented by S69-W 038 ischaracteristic of production of meteoric exposure,the third group represented by S80-W 064 related to marine en-vironment or transition zone between meteoric and marine or burial diagenetic environment;However,it can notexclude the possibility of deep-burial origin associated with thermal activities. While the fourth group representedby S85-W 005 is interpreted as burial origin with the high concentrated seawater,and appear to be related to a cer-taro acidation under the reduction condition.
In order to elucidate origin and pattern of cement calcites filled in fissure and cave,thirty-one calcite ce-ment samples collected in cavity and fissure in Ordovician carbonate of Tahe oilfield,Xmjiang were geochemicallyanalyzed,and the factor analysis and cluster analysis methods are used in such a large quantity of analytical data,the results show that:1.alcite cements are pure with the average mol%contents of CaCO3,MgCO3,FeCO3 andMnCO3 equal to 98.38,0. 87,0. 68 and 0. 07,respectively,and average content of SiO2,A12O3 equal to 1.95%and0. 73%,and Sr,BaO contain 131.4 X10-6 and 516. 5 X10-6 as well as F and C1 equal to 0. 014%and in 0. 013%,and the average ratio of (Mn+Fe)/Mg and Mn/ Fe equal 0. 87 and 0. 10,moreover,a linear covariance of Sr andMg concentrations of calcites expressed by the following relationship:Sr/ Ca=0. 00618Mg/ Ca+0.000533(Rz=0. 197),which indicates the abiotic origin of calcites;The six principle component consist of the major and traceelements with a certain of significant indication sedimentation factors and diagenetic environments;all of thesamples can be divided into four groups in cluster analysis,among them,the first group represented by S67-W 037and others document the characteristic of meteoric flushing product in phreatic wne and apparently undergone a se-ries of strong waterrock reactions or burial diagenetic reactions;the second group represented by S69-W 038 ischaracteristic of production of meteoric exposure,the third group represented by S80-W 064 related to marine en-vironment or transition zone between meteoric and marine or burial diagenetic environment;However,it can notexclude the possibility of deep-burial origin associated with thermal activities. While the fourth group representedby S85-W 005 is interpreted as burial origin with the high concentrated seawater,and appear to be related to a cer-taro acidation under the reduction condition.
2004, 22(1): 19-28.
Abstract:
The Late Carboniferous marine and non marine alternating deposits are well developed and outcropped in Xiaheyan of Zhongwei County, Ningxia Hui Autonomous Regionnorthwest China, including the Hongtuwa, Yanghugou and Taiyuan Formations. The facies analysis and sedimentary environment evolution are investigated in this study based on evidences of lithology, color, granularity analysis, facies indicator, geochemical data as well as fossil fauna and flora and Spore Pollen assemblages. Five facies are recognized including lagoon, tide flat, distributary bay estuarine sandbar, seashore and lowland marsh and tidal plainas well. In addition, the palaeogeographical background and sedimentary environmental evolution in Zhongwei of Ningxia are revealed and reconstructed based upon comparisons of the sedimentary characteristics with adjacent regions, including Eastern Sector of North Qilian, Ordos Basin and Taiyuan area of Northern China.
The Late Carboniferous marine and non marine alternating deposits are well developed and outcropped in Xiaheyan of Zhongwei County, Ningxia Hui Autonomous Regionnorthwest China, including the Hongtuwa, Yanghugou and Taiyuan Formations. The facies analysis and sedimentary environment evolution are investigated in this study based on evidences of lithology, color, granularity analysis, facies indicator, geochemical data as well as fossil fauna and flora and Spore Pollen assemblages. Five facies are recognized including lagoon, tide flat, distributary bay estuarine sandbar, seashore and lowland marsh and tidal plainas well. In addition, the palaeogeographical background and sedimentary environmental evolution in Zhongwei of Ningxia are revealed and reconstructed based upon comparisons of the sedimentary characteristics with adjacent regions, including Eastern Sector of North Qilian, Ordos Basin and Taiyuan area of Northern China.
2004, 22(1): 36-40.
Abstract:
The lacustrine environmental evolution of early Palaeogene Sanshui Basin has been established based on stable isotopic data from bulk carbonates from the Upper Xinzhuang Formation and the Honggang Member of the Buxin Formation (major oil source bed of the Basin). Three stages, when the basin had connection with the sea, have been recognized. With the transgression of sea waters and increased regional aridity, δ 18 O values showed a sharp positive shift, accompanied by the deposition of dolomites, whereas δ 13 C displayed lower values due to decomposition of organic matter that occurred at this time, which resulted in water rich in 13 C-depleted CO 2. During the intervals without connection with the sea, the δ 18 O and δ 13 C pattern showed a positive covariance (r = 0.65). This moderately high covariance, although poorer than that reported from typical closed lakes, suggests that the basin had, like most closed lakes, relatively long residence times. Gypsum deposits that occurred frequently in the core section also indicate hydrological closure conditions. This means that the Sanshui Basin was probably a periodic hydrologically closed lake during these times. The stable isotopic compositions of carbonates were mainly influenced by variations in evaporation/precipitation balance. Higher δ 18 O values indicate overall increase in E/P ratios, low lake levels and concentrated waters.Lower δ 18 O values suggest decrease in E/P ratios and a large fluvial inflow and a subsequent high stand of water level. δ 13 C shows more variability than δ 18 O, which implies that δ 13 C was also controlled by organic activity and usually reflects the productivity, burial vs. reoxidation of organic material.
The lacustrine environmental evolution of early Palaeogene Sanshui Basin has been established based on stable isotopic data from bulk carbonates from the Upper Xinzhuang Formation and the Honggang Member of the Buxin Formation (major oil source bed of the Basin). Three stages, when the basin had connection with the sea, have been recognized. With the transgression of sea waters and increased regional aridity, δ 18 O values showed a sharp positive shift, accompanied by the deposition of dolomites, whereas δ 13 C displayed lower values due to decomposition of organic matter that occurred at this time, which resulted in water rich in 13 C-depleted CO 2. During the intervals without connection with the sea, the δ 18 O and δ 13 C pattern showed a positive covariance (r = 0.65). This moderately high covariance, although poorer than that reported from typical closed lakes, suggests that the basin had, like most closed lakes, relatively long residence times. Gypsum deposits that occurred frequently in the core section also indicate hydrological closure conditions. This means that the Sanshui Basin was probably a periodic hydrologically closed lake during these times. The stable isotopic compositions of carbonates were mainly influenced by variations in evaporation/precipitation balance. Higher δ 18 O values indicate overall increase in E/P ratios, low lake levels and concentrated waters.Lower δ 18 O values suggest decrease in E/P ratios and a large fluvial inflow and a subsequent high stand of water level. δ 13 C shows more variability than δ 18 O, which implies that δ 13 C was also controlled by organic activity and usually reflects the productivity, burial vs. reoxidation of organic material.
2004, 22(1): 54-58.
Abstract:
The characteristics of macrolithology, fabric and rare earth elements of the immediate host siliceous rocks from Gaolong Gold Deposit suggest that they are of hydrothermal sedimentary origin, not of fracture breaking-hydrothermal silicified origin. Siliceous rocks probably deposited in transitional area between the continental margin and ocean basin environment, but closed to the continental margin, according to rock chemistry, rare earth elements and trace element geochemistry.
The characteristics of macrolithology, fabric and rare earth elements of the immediate host siliceous rocks from Gaolong Gold Deposit suggest that they are of hydrothermal sedimentary origin, not of fracture breaking-hydrothermal silicified origin. Siliceous rocks probably deposited in transitional area between the continental margin and ocean basin environment, but closed to the continental margin, according to rock chemistry, rare earth elements and trace element geochemistry.
2004, 22(1): 67-72.
Abstract:
On the basis of comprehensive study of seismic data, well logging and other data, applying the sequence stratigraphy theory, one supersequence set, four supersequences and ten sequences are distinguished in Dongying depression. We identify system tracts for each sequence and build up isochronous sequence framework in Dongying depression. The structural slope break zone, resulting in the abrupt change of the depositional slope, is initiated by the long term activity of syndepositional structure. Structural slope break zone in the fault subsidence lacustrine basin constrained the change in the accommodation space of the basins, controlling the development of the depositional sequence and the distribution of the depositional system tracts and the sand bodies. By means of establishing lower Tertiary equence stratigraphic framework and sequence system tract model of Dongying depression, this paper puts forward that lowstand sand bodies controlled by structural slope break zones are favorable for forming subtle reservoirs.
On the basis of comprehensive study of seismic data, well logging and other data, applying the sequence stratigraphy theory, one supersequence set, four supersequences and ten sequences are distinguished in Dongying depression. We identify system tracts for each sequence and build up isochronous sequence framework in Dongying depression. The structural slope break zone, resulting in the abrupt change of the depositional slope, is initiated by the long term activity of syndepositional structure. Structural slope break zone in the fault subsidence lacustrine basin constrained the change in the accommodation space of the basins, controlling the development of the depositional sequence and the distribution of the depositional system tracts and the sand bodies. By means of establishing lower Tertiary equence stratigraphic framework and sequence system tract model of Dongying depression, this paper puts forward that lowstand sand bodies controlled by structural slope break zones are favorable for forming subtle reservoirs.
2004, 22(1): 79-86.
Abstract:
Clay minerals and trace elements are disttibuted in different types of sand deposits and sedimentaryrocks. They are sensitive to environmental changes. The characteristics of clay minerals such as sedimentary differentiation, composition and assemblage, contents has recorded the information of environmental change during the processes of clay mineral formation. These information will help to reconstruct paleoenvironment with huge significance in the research of water depth change.By studing lithologic geochemical parameters of high resolution sequence units in differentsequences of the third memberand the fourth upper member of Shahejie formation in Shengbei fault's downwall side of Dongying depression,it has been found in pace of cyclicity of water depth controlledby paleoclimate during the formation period of high resolution sequence units,mineral composition(clay mienral and cement) of sedimentaryrocks,chemical constituents(trace element) would be cyclically changed.
Clay minerals and trace elements are disttibuted in different types of sand deposits and sedimentaryrocks. They are sensitive to environmental changes. The characteristics of clay minerals such as sedimentary differentiation, composition and assemblage, contents has recorded the information of environmental change during the processes of clay mineral formation. These information will help to reconstruct paleoenvironment with huge significance in the research of water depth change.By studing lithologic geochemical parameters of high resolution sequence units in differentsequences of the third memberand the fourth upper member of Shahejie formation in Shengbei fault's downwall side of Dongying depression,it has been found in pace of cyclicity of water depth controlledby paleoclimate during the formation period of high resolution sequence units,mineral composition(clay mienral and cement) of sedimentaryrocks,chemical constituents(trace element) would be cyclically changed.
2004, 22(1): 95-102.
Abstract:
The slope breaks are developed widespread in Jurassic large down warped lake basin, the Northwestern Area, Junggar Basin. Their genetic types can be divided into fracture slope break, bending slope break, sedimentary slope break and erosional slope break. For their showing mutual grades characteristics along source area direction, they also can be divided into basin margin slope break and inner basin slope break according to their natural geographical positions.The genetic mechanism of the slope breaks includes deep seated thrust structure, inherited paleohigh and interior basin secondary fault,etc., and the scale of slope breaks intimately relates with the size and the period of tectogenesis. Because of the variance of tectonic activity in different period and district range, the slope breaks formed by tectonic have multi period, episode, differential motion, inherited and invert characteristics. The slope breaks obviously control the stratigraphic overlap, the longitudinal lithologic combination and the longitudinal and lateral distribution of depositional systems. So, we establish a reasonable pattern that the slope breaks control nonstructural traps and guide the regional exploration of nonstructural traps, which has the significance to further prospect for large scale nonstructural traps and traps group.
The slope breaks are developed widespread in Jurassic large down warped lake basin, the Northwestern Area, Junggar Basin. Their genetic types can be divided into fracture slope break, bending slope break, sedimentary slope break and erosional slope break. For their showing mutual grades characteristics along source area direction, they also can be divided into basin margin slope break and inner basin slope break according to their natural geographical positions.The genetic mechanism of the slope breaks includes deep seated thrust structure, inherited paleohigh and interior basin secondary fault,etc., and the scale of slope breaks intimately relates with the size and the period of tectogenesis. Because of the variance of tectonic activity in different period and district range, the slope breaks formed by tectonic have multi period, episode, differential motion, inherited and invert characteristics. The slope breaks obviously control the stratigraphic overlap, the longitudinal lithologic combination and the longitudinal and lateral distribution of depositional systems. So, we establish a reasonable pattern that the slope breaks control nonstructural traps and guide the regional exploration of nonstructural traps, which has the significance to further prospect for large scale nonstructural traps and traps group.
2004, 22(1): 110-116.
Abstract:
Based on pioneer studies of lithostratigraphy, biostratigraphy and chronostratigraphy, authors analysed sequence stratigraphy and sedimentary microfacies of the Lower Middle Ordovician. Two sorts of sequence surfaces are discerned exposing sequence unconformities and drowing sequence unconformities. Three kinds of parasequence moulds are summaried as the tidal flat parasequences, the shoal parasequences and the shelf parasequences. Two main types of system tracts are formed by stacking patterns of parasequences transgressive systems tract and highstand systems tract. Based on these studies, Lower Middle Ordovician strata can be divided into 7 three grade sequences. Among these, The Sq1 2 three grade sequences are comparable with Penglaiba formation, the Sq3 6 three grade sequences are comparable with Yingshan formation and the Sq7 three grade sequence are comparable with Dwangou formation. The Sq1 2 three grade sequences are composed of penecontemporeous dolostones and carbonates tidal flat cycles, and the Sq3 6 three grade sequences are composed of tidal flat cycles and shoal cycles and the Sq7three grade sequences are composed of shelf facies carbonates.
Based on pioneer studies of lithostratigraphy, biostratigraphy and chronostratigraphy, authors analysed sequence stratigraphy and sedimentary microfacies of the Lower Middle Ordovician. Two sorts of sequence surfaces are discerned exposing sequence unconformities and drowing sequence unconformities. Three kinds of parasequence moulds are summaried as the tidal flat parasequences, the shoal parasequences and the shelf parasequences. Two main types of system tracts are formed by stacking patterns of parasequences transgressive systems tract and highstand systems tract. Based on these studies, Lower Middle Ordovician strata can be divided into 7 three grade sequences. Among these, The Sq1 2 three grade sequences are comparable with Penglaiba formation, the Sq3 6 three grade sequences are comparable with Yingshan formation and the Sq7 three grade sequence are comparable with Dwangou formation. The Sq1 2 three grade sequences are composed of penecontemporeous dolostones and carbonates tidal flat cycles, and the Sq3 6 three grade sequences are composed of tidal flat cycles and shoal cycles and the Sq7three grade sequences are composed of shelf facies carbonates.
2004, 22(1): 130-135.
Abstract:
Using the 210 Pb and 137 Cs dating methods in the sediment cores, the modern sedimentation rates in the contiguous sea area of Changjiang estuary and Hangzhou bay are estimated. The data show the obvious spatial distribution of sedimentation. To the east of the Shijiao Channel, less Changjiang's sediment inputs lead to the lower sedimentation rates because of the intrusion of high salinity water. To the west of the Shijiao Channel, the sea area between Changjiang estuary and Hangzhou bay is the main passage of the Changjiang's sediment southward diffusion. In the shoal area at the mouth of Hangzhou bay, the sedimentation rate reaches 3cm/a because of the sediment transportation effects of Changjiang estuarine plume and the Hangzhou tidal front. In the sea area of the Yangshan Port, the tidal channel with more than 20m waterdepth is being eroded while the shallow areas off the tidal channel accumulate slowly with 0.3～1.6cm/a. In the Majishan Port, which is located at a muddy slope along the the typical tidal channel, the sedimentation process is unstable. Although the normal sedimentation rate is 0.7 3.4cm/a, rapid accumulation and slipping of subbottom layer also frequently occur.
Using the 210 Pb and 137 Cs dating methods in the sediment cores, the modern sedimentation rates in the contiguous sea area of Changjiang estuary and Hangzhou bay are estimated. The data show the obvious spatial distribution of sedimentation. To the east of the Shijiao Channel, less Changjiang's sediment inputs lead to the lower sedimentation rates because of the intrusion of high salinity water. To the west of the Shijiao Channel, the sea area between Changjiang estuary and Hangzhou bay is the main passage of the Changjiang's sediment southward diffusion. In the shoal area at the mouth of Hangzhou bay, the sedimentation rate reaches 3cm/a because of the sediment transportation effects of Changjiang estuarine plume and the Hangzhou tidal front. In the sea area of the Yangshan Port, the tidal channel with more than 20m waterdepth is being eroded while the shallow areas off the tidal channel accumulate slowly with 0.3～1.6cm/a. In the Majishan Port, which is located at a muddy slope along the the typical tidal channel, the sedimentation process is unstable. Although the normal sedimentation rate is 0.7 3.4cm/a, rapid accumulation and slipping of subbottom layer also frequently occur.
2004, 22(1): 142-147.
Abstract:
In Longshou Mountains of the southwestern margins of North China. s Plate, there is extensively a se -ries of Pre -Cambrian sedimentary of the detrital flows consisting of dominant carbonate, and the sedimentary rockshave also been found in recent years. The rocks are characterized by chaotic gravels on grain sizes, dominantdolomite gravels, bed -rounded gravelsshowing angulate -subangulate, and textures of matrix support. In the regionthe sediments distributed continuously, but its thickness is various from several meters to tens of meters, locallytransforming to volcanic rocks. On the basis of the isotopic ages and micro -paleobotanic fossils of the over and un -derlain strata, the sedimentary rocks were suggested forming in late Neoproterozoic era. Its origin is thought to bethe sediments of the carbonate - fragmental flows, on a sedimentary- tectonic environment of paleo- continentalrift, coming from large quantities of collapse files on slope of continental rift due to crustal movement rapidly tolead to breakdown of sedimentary rocks on steady platform. So these rocks are the typical sediments of the cont- inental rift, and important significance on implication for the tectonic environments. In Longshou Mountains andneighboring area the distribution of large quantities of the late Neoprozoic sediments of palaeo- fargmental flowsindicate that in that time a large scale of continental rift had occurred and consistent with splitting recognition ofthe Rodinia continent globally.
In Longshou Mountains of the southwestern margins of North China. s Plate, there is extensively a se -ries of Pre -Cambrian sedimentary of the detrital flows consisting of dominant carbonate, and the sedimentary rockshave also been found in recent years. The rocks are characterized by chaotic gravels on grain sizes, dominantdolomite gravels, bed -rounded gravelsshowing angulate -subangulate, and textures of matrix support. In the regionthe sediments distributed continuously, but its thickness is various from several meters to tens of meters, locallytransforming to volcanic rocks. On the basis of the isotopic ages and micro -paleobotanic fossils of the over and un -derlain strata, the sedimentary rocks were suggested forming in late Neoproterozoic era. Its origin is thought to bethe sediments of the carbonate - fragmental flows, on a sedimentary- tectonic environment of paleo- continentalrift, coming from large quantities of collapse files on slope of continental rift due to crustal movement rapidly tolead to breakdown of sedimentary rocks on steady platform. So these rocks are the typical sediments of the cont- inental rift, and important significance on implication for the tectonic environments. In Longshou Mountains andneighboring area the distribution of large quantities of the late Neoprozoic sediments of palaeo- fargmental flowsindicate that in that time a large scale of continental rift had occurred and consistent with splitting recognition ofthe Rodinia continent globally.
2004, 22(1): 154-160.
Abstract:
On the exploration basis of detailed explanation of EASY%R o method, the process of maturation history computation, takingWell You 14 for an example,is illustrated and the maturation historyof source rocks in the 31 important exploration wells in the Western Qaidam Basin is simulated. Therefore, maturity contour diagramsof 5 series of source rock layers from lower member of lower Ganchaigou formation(E31)to upper Youshashan formation(N22) are drawn, and maturation historyof each source rocksis furthermore discussed in detail for these figures. This study has some significance for hydrocarbon accumulation investigation and oil exploration.
On the exploration basis of detailed explanation of EASY%R o method, the process of maturation history computation, takingWell You 14 for an example,is illustrated and the maturation historyof source rocks in the 31 important exploration wells in the Western Qaidam Basin is simulated. Therefore, maturity contour diagramsof 5 series of source rock layers from lower member of lower Ganchaigou formation(E31)to upper Youshashan formation(N22) are drawn, and maturation historyof each source rocksis furthermore discussed in detail for these figures. This study has some significance for hydrocarbon accumulation investigation and oil exploration.
2004, 22(1): 169-175.
Abstract:
Based on the research of the living examples of argillaceous rock in the Paleogene Neogene in Jiyang depression, both the occurrence of the organic matters and the characteristics of the pore structure are analysed. Then the pattern of the relationship between the expulsion path and the primary migration of hydrocarbon in the rock has been observed. The study shows that the pores are small but numerous, and the throats are narrow and thin in argillaceous rock, in which there is better sorting of pore throats, and a better interconnecting as well, besides, there are microfractures frequently observed there. When the argillaceous rocks containing more organic matter enter maturity stage, they are helpful to form thicker dissolved pores, and may easily produce more microfractures. This does not only favor the formation of abnormal pressure, but can delay the process of compact as well, therefore, which may protect the pore system. The occurrence of the organic matters in argillaceous rock can be classified into three types: the Enrichment Type, the Dispersion Type and the Partial Enrichment Type.(a) The Enrichment Type means that the organic matters are distributed plentifully along the bedding plane in the rock which deposited mainly in the finer clay particle and fewer detrital material (15%),and are rich in organic matter; (b) The Dispersion Type means that the organic matters are scattered respectively in the rock which deposited in the coarser clay particle and more detrital material (15%). This type of deposit of organic matters is various in abundance; (c) The Partial Enrichment Type has the properties of both the Enrichment Type and the Dispersion Type. By means of thicker pore throat system it becomes one of the ways through which the mature hydrocarbon can be exported from source rock when the organic matters occurred in Dispersion Type in argillaceous rock.When the organic matters are richer and occurred in the Enrichment Type in argillaceous rock,the binding and cementing of detritus and rock are weaker,besides,the fluid pressures are higher and can easily produce more microfractures. Therefore,they become the major path for primary migration of the mature hydrocarbon.
Based on the research of the living examples of argillaceous rock in the Paleogene Neogene in Jiyang depression, both the occurrence of the organic matters and the characteristics of the pore structure are analysed. Then the pattern of the relationship between the expulsion path and the primary migration of hydrocarbon in the rock has been observed. The study shows that the pores are small but numerous, and the throats are narrow and thin in argillaceous rock, in which there is better sorting of pore throats, and a better interconnecting as well, besides, there are microfractures frequently observed there. When the argillaceous rocks containing more organic matter enter maturity stage, they are helpful to form thicker dissolved pores, and may easily produce more microfractures. This does not only favor the formation of abnormal pressure, but can delay the process of compact as well, therefore, which may protect the pore system. The occurrence of the organic matters in argillaceous rock can be classified into three types: the Enrichment Type, the Dispersion Type and the Partial Enrichment Type.(a) The Enrichment Type means that the organic matters are distributed plentifully along the bedding plane in the rock which deposited mainly in the finer clay particle and fewer detrital material (15%),and are rich in organic matter; (b) The Dispersion Type means that the organic matters are scattered respectively in the rock which deposited in the coarser clay particle and more detrital material (15%). This type of deposit of organic matters is various in abundance; (c) The Partial Enrichment Type has the properties of both the Enrichment Type and the Dispersion Type. By means of thicker pore throat system it becomes one of the ways through which the mature hydrocarbon can be exported from source rock when the organic matters occurred in Dispersion Type in argillaceous rock.When the organic matters are richer and occurred in the Enrichment Type in argillaceous rock,the binding and cementing of detritus and rock are weaker,besides,the fluid pressures are higher and can easily produce more microfractures. Therefore,they become the major path for primary migration of the mature hydrocarbon.
