2004 Vol. 22, No. 4
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Display Method:
2004, 22(4): 560-565.
Abstract:
The climbing ripple cross lamination is especially well developed and widely distributed in the early Oligocene Yaxicuo Group sandstone of the Hoh Xil Basin, northern Tibetan Plateau. The small scale cross lamination is formed from the upward movement of sediment, when the source quickly provides too much new sediment. Two types of climbing ripple cross lamination, i.e. erosional stoss Type A and depositional stoss Type B1, are included in the Yaxicuo Group sandstone. Among that, a single set of Type A is about 2 cm in thickness and less than 7° for its climb angle; but a single set of Type B1 is about 4 cm in thickness and around 10° 20° for its climb angle. Three kinds of flows including non uniform, unsteady, and non uniform unsteady flows, which belong to sandy clastic flow and bottom flow, contributed their formation. The mean fluid velocity is generally 11 60 cm/s and the sediment deposition rate may be up to 0.1 g/cm2 s. The depositional environment is the delta front in shallow lake. The development of the Yaxicuo Group climbing ripple cross lamination could be under conditions of the early Oligocene uplift process of the Tibetan Plateau and global cooling and drying climate change.
The climbing ripple cross lamination is especially well developed and widely distributed in the early Oligocene Yaxicuo Group sandstone of the Hoh Xil Basin, northern Tibetan Plateau. The small scale cross lamination is formed from the upward movement of sediment, when the source quickly provides too much new sediment. Two types of climbing ripple cross lamination, i.e. erosional stoss Type A and depositional stoss Type B1, are included in the Yaxicuo Group sandstone. Among that, a single set of Type A is about 2 cm in thickness and less than 7° for its climb angle; but a single set of Type B1 is about 4 cm in thickness and around 10° 20° for its climb angle. Three kinds of flows including non uniform, unsteady, and non uniform unsteady flows, which belong to sandy clastic flow and bottom flow, contributed their formation. The mean fluid velocity is generally 11 60 cm/s and the sediment deposition rate may be up to 0.1 g/cm2 s. The depositional environment is the delta front in shallow lake. The development of the Yaxicuo Group climbing ripple cross lamination could be under conditions of the early Oligocene uplift process of the Tibetan Plateau and global cooling and drying climate change.
2004, 22(4): 573-578.
Abstract:
According to the in door flume experiment simulations, the formation of fluxoturbidite in front of delta is studied. It is summarized that there are four kinds of fluxoturbidite in front of delta. They are the fluxoturbidite with no trigger action and one associated with seismic process, one with wave action and sandstone lens correlative with landform. The experiments suggest that trigger actions are the most important conditions to form fluxoturbidite in front of delta. Together with wave action and seismic process, the change of landform can promote forming fluxoturbidite. Also, the fluxoturbidite can be found easily in front of the delta where the delta front has been destroyed and rebuilt. In contrast, the regular and good reserved delta front is disadvantaged to form fluxoturbidite.
According to the in door flume experiment simulations, the formation of fluxoturbidite in front of delta is studied. It is summarized that there are four kinds of fluxoturbidite in front of delta. They are the fluxoturbidite with no trigger action and one associated with seismic process, one with wave action and sandstone lens correlative with landform. The experiments suggest that trigger actions are the most important conditions to form fluxoturbidite in front of delta. Together with wave action and seismic process, the change of landform can promote forming fluxoturbidite. Also, the fluxoturbidite can be found easily in front of the delta where the delta front has been destroyed and rebuilt. In contrast, the regular and good reserved delta front is disadvantaged to form fluxoturbidite.
2004, 22(4): 588-596.
Abstract:
The Cambrian in the southeast of Qian is composed of typical carbonate rocks, which are widespread and better reservoirs. In order to understand the lithology, porosity and so on, in this paper, we took the Cambian in Sandu Danzhai to analyze petrographic feature in each layer and concluded the diagenetic environment of every formation of the Carbonate. Based on these study, we obtain the corresponding diagenesis which is responsible for producing the porosity of the rock, point out dolomitization is the main diagenesis in Duliujiang Formation of the mid Cambrian froming the larger and thicker carbonate rock, and dissolution pores produced by the burial dissolution is typical characters of the mid and upper Cambrian in the study area, burial dissolution is favorable for improving the reservoir physical properties. Recrystallization and compaction dissolution have also positive effect in producing porosity within the reservoir. This paper shows clearly the diagenetic evolution history of each formation within the Cambrian in the southeast of Guizhou province.
The Cambrian in the southeast of Qian is composed of typical carbonate rocks, which are widespread and better reservoirs. In order to understand the lithology, porosity and so on, in this paper, we took the Cambian in Sandu Danzhai to analyze petrographic feature in each layer and concluded the diagenetic environment of every formation of the Carbonate. Based on these study, we obtain the corresponding diagenesis which is responsible for producing the porosity of the rock, point out dolomitization is the main diagenesis in Duliujiang Formation of the mid Cambrian froming the larger and thicker carbonate rock, and dissolution pores produced by the burial dissolution is typical characters of the mid and upper Cambrian in the study area, burial dissolution is favorable for improving the reservoir physical properties. Recrystallization and compaction dissolution have also positive effect in producing porosity within the reservoir. This paper shows clearly the diagenetic evolution history of each formation within the Cambrian in the southeast of Guizhou province.
2004, 22(4): 603-608.
Abstract:
Carbon isotopic records from Europe, America, African, and Australia show two δ13 C positive excursions in the upper Devonian, which occur in the late rhenana and F F boundary, respectively. However, the pattern of δ13 C variations from southern China has not well been constrained. The negative δ13 C excursion was found in the early studies; however, the detailed study in the Dongcun section shows two δ13 C positive excursions in the upper Devonian. So further research is needed. The carbonate samples taken from Yandi section in Guilin, southern China have been analyzed for carbon isotopic and elemental compositions. The result shows two δ13 C positive excursions in the Upper Devonian. The first excursion occurred in the early rehnana zone, and the second around F F boundary, the later is a worldwide pattern. Compared with other records from different paleogeography units in the world, the F F carbon isotope excursion occurred in transition sequences has comparable shapes and amplitudes and,further support that they must be the result of a global increase in burial organic carbon.
Carbon isotopic records from Europe, America, African, and Australia show two δ13 C positive excursions in the upper Devonian, which occur in the late rhenana and F F boundary, respectively. However, the pattern of δ13 C variations from southern China has not well been constrained. The negative δ13 C excursion was found in the early studies; however, the detailed study in the Dongcun section shows two δ13 C positive excursions in the upper Devonian. So further research is needed. The carbonate samples taken from Yandi section in Guilin, southern China have been analyzed for carbon isotopic and elemental compositions. The result shows two δ13 C positive excursions in the Upper Devonian. The first excursion occurred in the early rehnana zone, and the second around F F boundary, the later is a worldwide pattern. Compared with other records from different paleogeography units in the world, the F F carbon isotope excursion occurred in transition sequences has comparable shapes and amplitudes and,further support that they must be the result of a global increase in burial organic carbon.
2004, 22(4): 621-627.
Abstract:
A film of pyrites was discovered on the interface of Lower Sinian Sidingshan Formation and Fengtai conglomerate, at Sishilichangshan Mountains in the south margin of the North China Block. The macroscopic, microscopic and geochemical studies of the film of pyrite reveal that the interface is a breakup unconformity. The discovery and determination of the breakup unconformity provides substantive proof for studying geological response of North China Block at the interval of Rodinia supercontinent breakup, and offers important tectonic background for studying the genesis of Fengtai conglomerate and its equivalence.
A film of pyrites was discovered on the interface of Lower Sinian Sidingshan Formation and Fengtai conglomerate, at Sishilichangshan Mountains in the south margin of the North China Block. The macroscopic, microscopic and geochemical studies of the film of pyrite reveal that the interface is a breakup unconformity. The discovery and determination of the breakup unconformity provides substantive proof for studying geological response of North China Block at the interval of Rodinia supercontinent breakup, and offers important tectonic background for studying the genesis of Fengtai conglomerate and its equivalence.
2004, 22(4): 644-650.
Abstract:
Based on drilling, logging and seismic data, classification correlation of sequence strata has been performed. Formation of lower Cretaceous can be divided into 3 super sequences and 6 tertiary sequences. Lithology, sedimentary facies, system development and formation stacking have also been studied. After these study we could clearly understand the background of sequence formation, deposition evolution, development of source reservoir seal and their association. It is believed that the evolution of Baiyinchagan depression began at its early stage with inherited development and reached its peak at late stage. The depression lasted three flooding, forming three sets of source rocks, which developed 4 types of sandbody with 3 sets of reservoir seal assemblage.
Based on drilling, logging and seismic data, classification correlation of sequence strata has been performed. Formation of lower Cretaceous can be divided into 3 super sequences and 6 tertiary sequences. Lithology, sedimentary facies, system development and formation stacking have also been studied. After these study we could clearly understand the background of sequence formation, deposition evolution, development of source reservoir seal and their association. It is believed that the evolution of Baiyinchagan depression began at its early stage with inherited development and reached its peak at late stage. The depression lasted three flooding, forming three sets of source rocks, which developed 4 types of sandbody with 3 sets of reservoir seal assemblage.
2004, 22(4): 658-663.
Abstract:
Magnetic properties of sediments from the Changjiang and the Huanghe Estuaries have been studied on the basis of magnetic measurement and grain size analysis. The results show that the magnetic properties of the sediments are dominated by ferrimagnetic magnetite, and higher concentration of ferrimagnetic minerals is observed for the Changjiang Estuary sediments. The pseudo single domain and multi domain particles are the main carriers of the ferrimagetic magnetite of the sediments in the Changjiang and Huanghe Estuaries, and single domain and superparamagnetic particles are also present in the sediments with higher concentration occuring in the Changjiang Estuary. The magnetic properties of sediments from the Changjiang and the Huanghe Estuaries suggested that the provenance of sediments controlled the magnetic features. At the same time, obvious correlation exists between χ ARM、 χ fd % and fine particles of the sediments in the Changjiang and Huanghe estuaries.
Magnetic properties of sediments from the Changjiang and the Huanghe Estuaries have been studied on the basis of magnetic measurement and grain size analysis. The results show that the magnetic properties of the sediments are dominated by ferrimagnetic magnetite, and higher concentration of ferrimagnetic minerals is observed for the Changjiang Estuary sediments. The pseudo single domain and multi domain particles are the main carriers of the ferrimagetic magnetite of the sediments in the Changjiang and Huanghe Estuaries, and single domain and superparamagnetic particles are also present in the sediments with higher concentration occuring in the Changjiang Estuary. The magnetic properties of sediments from the Changjiang and the Huanghe Estuaries suggested that the provenance of sediments controlled the magnetic features. At the same time, obvious correlation exists between χ ARM、 χ fd % and fine particles of the sediments in the Changjiang and Huanghe estuaries.
2004, 22(4): 672-675.
Abstract:
The contents of organic carbon and nitrogen were measured and DNA was extracted in the sediments of Lake Erhai. The distribution of organic carbon and nitrogen is consistent, i.e. degradation of organic carbon and nitrogen occurred in 10cm surface sediments and the modes of degradation change at 7cm, resulting in the different characteristics. Using the methods of molecular biology connecting with geochemistry, diagenesis process can be understood deeply.
The contents of organic carbon and nitrogen were measured and DNA was extracted in the sediments of Lake Erhai. The distribution of organic carbon and nitrogen is consistent, i.e. degradation of organic carbon and nitrogen occurred in 10cm surface sediments and the modes of degradation change at 7cm, resulting in the different characteristics. Using the methods of molecular biology connecting with geochemistry, diagenesis process can be understood deeply.
2004, 22(4): 683-688.
Abstract:
The natural gases of Kela 2 and Ake 1 are similarly very "dry" in component and more "heavier" in carbon isotopes, such as dry coefficient (bulk ratio of methane to total hydrocarbons) of Kela 2 gas and Ake 1gas near 1.0, δ13 C1 value (methane carbon isotopic ratio) from -27.3‰ to-31.1‰ for Kela 2 gas and from -21.9‰ to -25.2‰ for Ake 1gas. According to the data by traditional interpretation, the gases could derived measure strata source rock with over maturity. But, the maturity of the gases through calculation were much higher than the maturity of source rocks by determined or by basin analysis. So, when data of Kela 2 gas and Ake 1 gas are explained, the effect on the gases by filling process must be emphasized. In this paper, it is stated the main cause that the Kela 2 gas and Ake 1 gas tend to be dry and bear heavier isotope composition lies in the filling process with gas partial accumulation in late period.
The natural gases of Kela 2 and Ake 1 are similarly very "dry" in component and more "heavier" in carbon isotopes, such as dry coefficient (bulk ratio of methane to total hydrocarbons) of Kela 2 gas and Ake 1gas near 1.0, δ13 C1 value (methane carbon isotopic ratio) from -27.3‰ to-31.1‰ for Kela 2 gas and from -21.9‰ to -25.2‰ for Ake 1gas. According to the data by traditional interpretation, the gases could derived measure strata source rock with over maturity. But, the maturity of the gases through calculation were much higher than the maturity of source rocks by determined or by basin analysis. So, when data of Kela 2 gas and Ake 1 gas are explained, the effect on the gases by filling process must be emphasized. In this paper, it is stated the main cause that the Kela 2 gas and Ake 1 gas tend to be dry and bear heavier isotope composition lies in the filling process with gas partial accumulation in late period.
2004, 22(4): 694-699.
Abstract:
For a crude oil sample from Ordovician reservoir in Well Caogu100 Ping 19 in Jiyang depression, Shengli Oilfield, North China, hydrocarbons except for tricyclic terpane, hopane and 25 norhopane homologues were completely depleted in saturated fraction, as well as hydrocarbons except for triaromatic steranes in the aromatic fraction, which indicate that severe biodegradation occurred in this reservoir. Completely depleted n alkanes unaltered by water washing and dibenzothiphenes resistant biodegradation in the oil sample implied apparently that the alteration occurred in this reservoir was associated with biodegradation together with water washing. The magnitude of "UCM" hump existed in the aromatic fraction is apparently larger than that of "UCM" hump existed in the saturated fraction, which implied that the biodegradation rate for aromatic hydrocarbons is parallel or even exceed that of the saturated hydrocarbons. The fast biodegradation of aromatic hydrocarbons with lower molecular weight, as well as the occurrence of abundant 25 norhopanes, indicates that the alteration occurred in the aerobic environment other than in the anaerobic condition.
For a crude oil sample from Ordovician reservoir in Well Caogu100 Ping 19 in Jiyang depression, Shengli Oilfield, North China, hydrocarbons except for tricyclic terpane, hopane and 25 norhopane homologues were completely depleted in saturated fraction, as well as hydrocarbons except for triaromatic steranes in the aromatic fraction, which indicate that severe biodegradation occurred in this reservoir. Completely depleted n alkanes unaltered by water washing and dibenzothiphenes resistant biodegradation in the oil sample implied apparently that the alteration occurred in this reservoir was associated with biodegradation together with water washing. The magnitude of "UCM" hump existed in the aromatic fraction is apparently larger than that of "UCM" hump existed in the saturated fraction, which implied that the biodegradation rate for aromatic hydrocarbons is parallel or even exceed that of the saturated hydrocarbons. The fast biodegradation of aromatic hydrocarbons with lower molecular weight, as well as the occurrence of abundant 25 norhopanes, indicates that the alteration occurred in the aerobic environment other than in the anaerobic condition.
2004, 22(4): 707-710.
Abstract:
Nitrogen isotopic ratio of several oils with different physical and chemical qualities from Lengdong zone in Liaohe oil field is analyzed to understand the mechanism of nitrogen isotopic fractionation and the metabolism of nitrogen bearing compounds during biodegradation in this paper. The δ 15 N of normal oil is about 4.0‰ approaching to that of the kerogen whereas the δ 15 N of biodegraded oil increases obviously with the value close to or over 10.0‰. Moreover, the δ 15 N vary with the degree of degradation. The fact that nitrogen isotopic fractionation has occurred during the oil biodegradation suggests that nitrogen bearing organic compounds in oils be involved in the metabolism of bacteria.
Nitrogen isotopic ratio of several oils with different physical and chemical qualities from Lengdong zone in Liaohe oil field is analyzed to understand the mechanism of nitrogen isotopic fractionation and the metabolism of nitrogen bearing compounds during biodegradation in this paper. The δ 15 N of normal oil is about 4.0‰ approaching to that of the kerogen whereas the δ 15 N of biodegraded oil increases obviously with the value close to or over 10.0‰. Moreover, the δ 15 N vary with the degree of degradation. The fact that nitrogen isotopic fractionation has occurred during the oil biodegradation suggests that nitrogen bearing organic compounds in oils be involved in the metabolism of bacteria.
2004, 22(4): 718-723.
Abstract:
The gas potential and generation model of type Ⅰ,Ⅱ 1,Ⅱ 2 and Ⅲ organic matter in the open system have been studied. The thermal simulations with type Ⅱ 1 organic matter in the open and closed pyrolysis systems have been carried out and gas generation potential and model have been compared in the two kinds of systems. In the open system the gas potential from type Ⅰ is the highest and its potential is about 269.6 l/g·C org . The gas potential from type Ⅲ is the lowest and its potential is only 26.3 l/g · C org . The gas potential from type Ⅱ 1 in the closed system is more than that in the open system. In the closed system the gas potential is up to 371.2 l/g·C org ., which is about 4.4 times higher than that in the open system. This means that the cracking mechanisms are not different in these two kinds of pyrolysis systems. In the open system, the gas is mainly generated from kerogen by primary cracking, but in the closed system it is generated from kerogen and liquid hydrocarbon by primary and secondary cracking. The gas generation model from type Ⅱ 1 is different in this two kinds of cracking process. The main evolution stage of gas generation by primary cracking (from kerogen) is from R o(%)=1.0 to 1.5 and that by secondary cracking (from liquid hydrocarbon) is from R o(%)=1.5 to 2.5.
The gas potential and generation model of type Ⅰ,Ⅱ 1,Ⅱ 2 and Ⅲ organic matter in the open system have been studied. The thermal simulations with type Ⅱ 1 organic matter in the open and closed pyrolysis systems have been carried out and gas generation potential and model have been compared in the two kinds of systems. In the open system the gas potential from type Ⅰ is the highest and its potential is about 269.6 l/g·C org . The gas potential from type Ⅲ is the lowest and its potential is only 26.3 l/g · C org . The gas potential from type Ⅱ 1 in the closed system is more than that in the open system. In the closed system the gas potential is up to 371.2 l/g·C org ., which is about 4.4 times higher than that in the open system. This means that the cracking mechanisms are not different in these two kinds of pyrolysis systems. In the open system, the gas is mainly generated from kerogen by primary cracking, but in the closed system it is generated from kerogen and liquid hydrocarbon by primary and secondary cracking. The gas generation model from type Ⅱ 1 is different in this two kinds of cracking process. The main evolution stage of gas generation by primary cracking (from kerogen) is from R o(%)=1.0 to 1.5 and that by secondary cracking (from liquid hydrocarbon) is from R o(%)=1.5 to 2.5.
2004, 22(4): 729-736.
Abstract:
On the basis of biomarkers in Carboniferous source rocks and coals from the northeastern portion of Qaidam basin, it can be seen that these samples have reached high maturation stage during their thermal evolution, and the organic sources are mainly from aquatic organisms combined with abundant terrigenous input. Apart from SH-79 coal sample formed in more oxidizing environment, most of samples in this study deposited in reducing environment with saline water with medium and high content of total organic matter. Thus, the Carboniferous paralic coal-bearing stratum is a set of excellent source rock measures with much better hydrocarbon generation potential than Jurassic source rocks.
On the basis of biomarkers in Carboniferous source rocks and coals from the northeastern portion of Qaidam basin, it can be seen that these samples have reached high maturation stage during their thermal evolution, and the organic sources are mainly from aquatic organisms combined with abundant terrigenous input. Apart from SH-79 coal sample formed in more oxidizing environment, most of samples in this study deposited in reducing environment with saline water with medium and high content of total organic matter. Thus, the Carboniferous paralic coal-bearing stratum is a set of excellent source rock measures with much better hydrocarbon generation potential than Jurassic source rocks.
2004, 22(4): 743-749.
Abstract:
Organic -inorganic reactions in the process TSR (Thermochemical Sulfate Reduction) are the main reasons to re - sult in hydrocarbon disappearance. Metal sulfide formation is very important in geochemical cycle of C -S -O system. In this paper, thermal simulation experiments were carried out using autoclave at definite temperature and pressure. The properties of the products were characterized by X -ray diffraction method to investigate the reaction pathway. The thermodynamics and kinetics of H 2 S -Fe 2 O 3 systemswere discussed. It is found that H 2 S -Fe 2 O 3 reaction can proceed spontaneously and increasing temperature is disfavored for H 2 S -Fe 2 O 3 system. The products of H 2 S -Fe 2 O 3 systems were complex Fe -S materials and the primary compound is FeS 2 . On the basis of the experimental data, the reaction mechanism was discussed tentatively. The study on the formation of ferric sulfide in the TSR system for the carbonate rock is a novel way to explain the organic -inor - ganic reactions in deep environment. Further research on this subject is necessary in the future to understand more details of the TSR system and issue of hydrocarbon destruction in gas reservoirs.
Organic -inorganic reactions in the process TSR (Thermochemical Sulfate Reduction) are the main reasons to re - sult in hydrocarbon disappearance. Metal sulfide formation is very important in geochemical cycle of C -S -O system. In this paper, thermal simulation experiments were carried out using autoclave at definite temperature and pressure. The properties of the products were characterized by X -ray diffraction method to investigate the reaction pathway. The thermodynamics and kinetics of H 2 S -Fe 2 O 3 systemswere discussed. It is found that H 2 S -Fe 2 O 3 reaction can proceed spontaneously and increasing temperature is disfavored for H 2 S -Fe 2 O 3 system. The products of H 2 S -Fe 2 O 3 systems were complex Fe -S materials and the primary compound is FeS 2 . On the basis of the experimental data, the reaction mechanism was discussed tentatively. The study on the formation of ferric sulfide in the TSR system for the carbonate rock is a novel way to explain the organic -inor - ganic reactions in deep environment. Further research on this subject is necessary in the future to understand more details of the TSR system and issue of hydrocarbon destruction in gas reservoirs.
2004, 22(4): 566-572.
Abstract:
The Early Cretaceous Heishidu Formation (HsdF), distributed between the southern Xiaotian Mozitang fault (XMF) and northern Jinzhai Xianghongdian Xitanchi fault in the north margin of the Dabie Mountains, elongates in east westward, and thickness is more than 1 km. The lithofacies are mainly composed of Bcm, Gcg, Gcm, Gm, Sg, Ss, Fc, Fm, Fr, C and so on, and depositional systems include alluvial fan, fluvial, fan delta and lacustrine deposits, and fluvial deposits are mainly composed of sediments of floodplain and crevasse splays. HsdF developed the fining upward sequences, and alluvial fan in the early stage, floodplain and crevasse splay and fan delta in the middle stage, and lacustrine turbidites in the late stage. Alluvial fan and lacustrine turbidites mainly developed in Xiaotian area on the eastern part of the basin, floodplain and crevasse splay in Huoshan area on the western, and fan delta on both parts. The basin might be attributed to an asymmetric down faulted lake, and its evolution might be controlled by XMF.
The Early Cretaceous Heishidu Formation (HsdF), distributed between the southern Xiaotian Mozitang fault (XMF) and northern Jinzhai Xianghongdian Xitanchi fault in the north margin of the Dabie Mountains, elongates in east westward, and thickness is more than 1 km. The lithofacies are mainly composed of Bcm, Gcg, Gcm, Gm, Sg, Ss, Fc, Fm, Fr, C and so on, and depositional systems include alluvial fan, fluvial, fan delta and lacustrine deposits, and fluvial deposits are mainly composed of sediments of floodplain and crevasse splays. HsdF developed the fining upward sequences, and alluvial fan in the early stage, floodplain and crevasse splay and fan delta in the middle stage, and lacustrine turbidites in the late stage. Alluvial fan and lacustrine turbidites mainly developed in Xiaotian area on the eastern part of the basin, floodplain and crevasse splay in Huoshan area on the western, and fan delta on both parts. The basin might be attributed to an asymmetric down faulted lake, and its evolution might be controlled by XMF.
2004, 22(4): 579-587.
Abstract:
The Permian Chihsia Formation of South China is a unique carbonate succession, which is rich in organic matter and chert nodule, and is characterized by the great lateral persistence with little variation in lithofacies and strata thickness. Two special diagenetic minerals, nodular celestite and sepiolite, are developed in the carbonate succession. Comprehensions on the origin of the above mentioned features implied that oxygen deficient environmental condition was a critical controlling factor among these features. Based on sedimentary features of the carbonate succession, it was proposed that the Chihsian deficient environments were derived from relatively high bioproductivity. This explanation is compatible with recent advancements in the Permian paleocliamatology and paleoceanography, but further work on the origin of the high bioproductivity is still desired.
The Permian Chihsia Formation of South China is a unique carbonate succession, which is rich in organic matter and chert nodule, and is characterized by the great lateral persistence with little variation in lithofacies and strata thickness. Two special diagenetic minerals, nodular celestite and sepiolite, are developed in the carbonate succession. Comprehensions on the origin of the above mentioned features implied that oxygen deficient environmental condition was a critical controlling factor among these features. Based on sedimentary features of the carbonate succession, it was proposed that the Chihsian deficient environments were derived from relatively high bioproductivity. This explanation is compatible with recent advancements in the Permian paleocliamatology and paleoceanography, but further work on the origin of the high bioproductivity is still desired.
2004, 22(4): 597-602.
Abstract:
Experiments were performed to investigate the effects of mono functional and bi functional carboxylic acids on microcline at different temperatures. The experimental results are as follows: As temperatures arises, the concentrations and mobility of Al, SiO2 and other components are enhanced to allow rapid dissolution of microclines. At low pH, dissolution of microclines control with pH. However, pH is probably not significant under moderately acidic conditions. Date from these experiments indicate that oxalic and acetic acids reacting with microclines at different temperatures can enhance the solubility of Al and other cat ions and create secondary porosity, although oxalate has a much greater effect than acetate. Although organic acids can enhance substantially the solubility of Al, organic anion aluminum complexes prefer oil to water. So the concentrations of Al in the oilfield waters are low.
Experiments were performed to investigate the effects of mono functional and bi functional carboxylic acids on microcline at different temperatures. The experimental results are as follows: As temperatures arises, the concentrations and mobility of Al, SiO2 and other components are enhanced to allow rapid dissolution of microclines. At low pH, dissolution of microclines control with pH. However, pH is probably not significant under moderately acidic conditions. Date from these experiments indicate that oxalic and acetic acids reacting with microclines at different temperatures can enhance the solubility of Al and other cat ions and create secondary porosity, although oxalate has a much greater effect than acetate. Although organic acids can enhance substantially the solubility of Al, organic anion aluminum complexes prefer oil to water. So the concentrations of Al in the oilfield waters are low.
2004, 22(4): 609-613.
Abstract:
The hydrothermal sediments from Jade hydrothermal field are mainly composed of massive sulfide ore and massive sulfate ore. The massive sulfide ore is characterized as the richness of Pb and Ag. According to electron microprobe analysis and neutron activation analysis, silver is mainly rich in the coarse grained sulfide and fine grained sulfide aggregate as dispersion regime in the massive sulfide ore. Silver enrichment mineralization occurs in the early and late period of hydrothermal activity. In the massive sulfate ores mainly composed of anhydrite, silver is rich in the fine grained sulfide aggregate at dispersion regime. Silver is rich at above 150 degree centigrade in the middle late period of hydrothermal activity. Natural silver is found in sulfate ores mainly composed of barite for the first time, which is the major regime of concentration for silver. Silver enrichment mineralization occurs at below 160 degree centigrade in the late period of hydrothermal activity.
The hydrothermal sediments from Jade hydrothermal field are mainly composed of massive sulfide ore and massive sulfate ore. The massive sulfide ore is characterized as the richness of Pb and Ag. According to electron microprobe analysis and neutron activation analysis, silver is mainly rich in the coarse grained sulfide and fine grained sulfide aggregate as dispersion regime in the massive sulfide ore. Silver enrichment mineralization occurs in the early and late period of hydrothermal activity. In the massive sulfate ores mainly composed of anhydrite, silver is rich in the fine grained sulfide aggregate at dispersion regime. Silver is rich at above 150 degree centigrade in the middle late period of hydrothermal activity. Natural silver is found in sulfate ores mainly composed of barite for the first time, which is the major regime of concentration for silver. Silver enrichment mineralization occurs at below 160 degree centigrade in the late period of hydrothermal activity.
2004, 22(4): 628-635.
Abstract:
Arc shaped fault system of Dongying depression is composed of 3 circle belts. Syndepositional faulting in these circle belts caused the development of syndeposotional fault break slope, which further controlled the distribution of subsidence centers, hydrocarbon generating center and sand bodies. Big low stand fan sand bodies that have been found distribute along the circle belts and were controlled by fault break slopes. Thus, important direction of finding new low stand reservoirs should be from fault break slope to sag depression along sequence boundary. Moreover, based on the analysis of hydrocarbon generating dynamics, migration systems and relationship between reservoirs and effective hydrocarbon rocks, two kinds of hydrocarbon accumulation models have been put forward in this paper. The low stand fans in fault break mainly are almost all favorable reservoirs for oil and gas, and show similar dynamic progress of hydrocarbon accumulation.
Arc shaped fault system of Dongying depression is composed of 3 circle belts. Syndepositional faulting in these circle belts caused the development of syndeposotional fault break slope, which further controlled the distribution of subsidence centers, hydrocarbon generating center and sand bodies. Big low stand fan sand bodies that have been found distribute along the circle belts and were controlled by fault break slopes. Thus, important direction of finding new low stand reservoirs should be from fault break slope to sag depression along sequence boundary. Moreover, based on the analysis of hydrocarbon generating dynamics, migration systems and relationship between reservoirs and effective hydrocarbon rocks, two kinds of hydrocarbon accumulation models have been put forward in this paper. The low stand fans in fault break mainly are almost all favorable reservoirs for oil and gas, and show similar dynamic progress of hydrocarbon accumulation.
2004, 22(4): 651-657.
Abstract:
Piston Core DGKS9617, which is located in northern part of the East China Sea, is divided into two sedimentary facies: tidal shallow marine facies (55 851cm), in which tidal current played an important role in the sedimentation of this part, and shallow marine facies (0 55cm). Although the lower and the upper part has different sedimentary environment, the provenance of the whole core does not change. The character of heavy mineral assemblage, the results of discrimination function of Fe, Mn, V, Cr, Ni, Cu, Zn, carbonate analysis and Ba Sr Zn ternary diagram consistently show that the mineral and geochemical characteristics of Core DGKS9617 are similar to the Changjiang River sediment, implying that its sediment is mainly provided by the Changjiang River.
Piston Core DGKS9617, which is located in northern part of the East China Sea, is divided into two sedimentary facies: tidal shallow marine facies (55 851cm), in which tidal current played an important role in the sedimentation of this part, and shallow marine facies (0 55cm). Although the lower and the upper part has different sedimentary environment, the provenance of the whole core does not change. The character of heavy mineral assemblage, the results of discrimination function of Fe, Mn, V, Cr, Ni, Cu, Zn, carbonate analysis and Ba Sr Zn ternary diagram consistently show that the mineral and geochemical characteristics of Core DGKS9617 are similar to the Changjiang River sediment, implying that its sediment is mainly provided by the Changjiang River.
2004, 22(4): 664-671.
Abstract:
Few fossils were found previously in early Early Cambrian black shale, such as sponges. With the deepening of the research, many phyla have been discovered recently. A lot of carbon fossils were found in early Early Cambrian black shale of Guizhou Province, south China, and they are simple trace fossils, carbon Phyllocarida, complete sponges, Platysolenites, Bivalvia, carbon Hyolitha, "Worm", bryozoa like animal fossil and membrane discus fossils. Mineral composition of the black shale in the base Cambrian, Kaiyang County, Guizhou, China was analyzed by XRD analyses, according to the change of mineral composition of black shale and geochemical character in Kaiyang section, authors suggest that a prosperous period of large animal between small shell animal and the Chengjiang fauna was present, this animal assemblage disappear as crustal expansion, mass submarine hydrothermal event and volcanic eruption, the early Early Cambrian seawater changed from the weak alkalinity to weak acidity, animal did not live at the weak acidity, so large animals between small shell animal and the Chengjiang fauna disappeared. With the recovering of weak alkalinity of the seawater, a prosperous period of animal, the Chengjiang fauna was present.
Few fossils were found previously in early Early Cambrian black shale, such as sponges. With the deepening of the research, many phyla have been discovered recently. A lot of carbon fossils were found in early Early Cambrian black shale of Guizhou Province, south China, and they are simple trace fossils, carbon Phyllocarida, complete sponges, Platysolenites, Bivalvia, carbon Hyolitha, "Worm", bryozoa like animal fossil and membrane discus fossils. Mineral composition of the black shale in the base Cambrian, Kaiyang County, Guizhou, China was analyzed by XRD analyses, according to the change of mineral composition of black shale and geochemical character in Kaiyang section, authors suggest that a prosperous period of large animal between small shell animal and the Chengjiang fauna was present, this animal assemblage disappear as crustal expansion, mass submarine hydrothermal event and volcanic eruption, the early Early Cambrian seawater changed from the weak alkalinity to weak acidity, animal did not live at the weak acidity, so large animals between small shell animal and the Chengjiang fauna disappeared. With the recovering of weak alkalinity of the seawater, a prosperous period of animal, the Chengjiang fauna was present.
2004, 22(4): 676-682.
Abstract:
Based on the lithostratigraphical subdivision with reference to the chronological data in the Milanggouwan section located at Salawusu River Valley of the southeastern margin of Mu Us Desert, Ordos Plateau, China, some ideas have been put forward in the paper: 1 The sedimentary ages of the lithostratigraphical units as indicated by formations in the section are that Lishi Formation was formed at 150000a B. P., Salawusu Formation 150000 75000a B. P., Chengchuan Formation 75000-10000a B. P., Dagouwan and Dishaogouwan Formations 10000 1000a B. P. and Fanjiagouwan Formation 1000a B. P. to present. 2 Geochronologically, the above mentioned lithostratigraphical units can be well correla ted with those in the Loess Plateau, China. Lishi Formation\Salawusu Formation, Salawusu Formation\Chengchuan Formation and Chengchuan Formation\Dagouwan and Dishaogouwan and Fanjiagouwan Formations correspond in succession to L2 \S1 (the time limit is 140000 a B. P.), S1 \L1 (80000 a B. P.) and L 1 \S0 (11000 10000 a B. P.). 3 In light of the past global variation, the lithostratigraphical units, at present, can assuredly be compared with the recent several oxygen-isotop stages in the deep sea and continental glacier regions, which are showed by ""as: Lishi Formation MIS6, Salawusu Formation MIS5, Chengchuan Formation MIS2～MIS4, Dagouwan, Dishaogouwan and Fanjiagouwan Formations MIS1. The correlative relation clearly indicates that the environmental evolution in 10000a scale in Chinese desert, like the Chinese loess, were affected to a great extent by the climatic fluctuations between glacial and interglacial periods in the Northern Hemisphere. According to climate stratigraphy, hereby,the Formations of Lishi, Salawusu, Chengchuan, Dagouwan and Dishaogouwan and Fanjiagouwan may be regarded as Riss Glacial Period, Riss Würm Interglacial Period (Last Interglacial Period), Würm Glacial Period (Last Glacial Period) and Post Glacial Period.
Based on the lithostratigraphical subdivision with reference to the chronological data in the Milanggouwan section located at Salawusu River Valley of the southeastern margin of Mu Us Desert, Ordos Plateau, China, some ideas have been put forward in the paper: 1 The sedimentary ages of the lithostratigraphical units as indicated by formations in the section are that Lishi Formation was formed at 150000a B. P., Salawusu Formation 150000 75000a B. P., Chengchuan Formation 75000-10000a B. P., Dagouwan and Dishaogouwan Formations 10000 1000a B. P. and Fanjiagouwan Formation 1000a B. P. to present. 2 Geochronologically, the above mentioned lithostratigraphical units can be well correla ted with those in the Loess Plateau, China. Lishi Formation\Salawusu Formation, Salawusu Formation\Chengchuan Formation and Chengchuan Formation\Dagouwan and Dishaogouwan and Fanjiagouwan Formations correspond in succession to L2 \S1 (the time limit is 140000 a B. P.), S1 \L1 (80000 a B. P.) and L 1 \S0 (11000 10000 a B. P.). 3 In light of the past global variation, the lithostratigraphical units, at present, can assuredly be compared with the recent several oxygen-isotop stages in the deep sea and continental glacier regions, which are showed by ""as: Lishi Formation MIS6, Salawusu Formation MIS5, Chengchuan Formation MIS2～MIS4, Dagouwan, Dishaogouwan and Fanjiagouwan Formations MIS1. The correlative relation clearly indicates that the environmental evolution in 10000a scale in Chinese desert, like the Chinese loess, were affected to a great extent by the climatic fluctuations between glacial and interglacial periods in the Northern Hemisphere. According to climate stratigraphy, hereby,the Formations of Lishi, Salawusu, Chengchuan, Dagouwan and Dishaogouwan and Fanjiagouwan may be regarded as Riss Glacial Period, Riss Würm Interglacial Period (Last Interglacial Period), Würm Glacial Period (Last Glacial Period) and Post Glacial Period.
2004, 22(4): 689-693.
Abstract:
Artificial mixed experiment and geochemical characteristics of mixed oils between coal formed oil and Paleocene Tertiary oil from Suqiao-Wenan Area in Jidong Depression have been analyzed and studied systematically, the results suggest that the absolute amounts of C19 tricyclic terpene, C24 tetracyclic terpane,C30 diahopane, C29 sterane and diasteranes are decreasing due to the increasing of Paleocene Tertiary oil in mixed oils. In contrast, the absolute amounts of pristane, phytane, gammacerane, C27 sterane are increasing. Quantitative identification model of mixed oils from Suqiao wenan area in Jidong depression have been established based on geochemical characteristics of the absolute amounts for saturated hydrocarbon biomarkers and polycyclic aromatic hydrocarbons. According to the geochemical model of our study, crude oil of Well Su 49 consists of approximately 10% Paleocene Tertiary oil and 90% coal formed oil, and the crude oil of Well Wen102 1 consists of approximately 90% Paleocene Tertiary oil and 10% coal formed oil.
Artificial mixed experiment and geochemical characteristics of mixed oils between coal formed oil and Paleocene Tertiary oil from Suqiao-Wenan Area in Jidong Depression have been analyzed and studied systematically, the results suggest that the absolute amounts of C19 tricyclic terpene, C24 tetracyclic terpane,C30 diahopane, C29 sterane and diasteranes are decreasing due to the increasing of Paleocene Tertiary oil in mixed oils. In contrast, the absolute amounts of pristane, phytane, gammacerane, C27 sterane are increasing. Quantitative identification model of mixed oils from Suqiao wenan area in Jidong depression have been established based on geochemical characteristics of the absolute amounts for saturated hydrocarbon biomarkers and polycyclic aromatic hydrocarbons. According to the geochemical model of our study, crude oil of Well Su 49 consists of approximately 10% Paleocene Tertiary oil and 90% coal formed oil, and the crude oil of Well Wen102 1 consists of approximately 90% Paleocene Tertiary oil and 10% coal formed oil.
2004, 22(4): 700-706.
Abstract:
The western slope of Songliao Basin spans two oil areas of Daqing and Jilin and its prospecting area is about 4.3×10 4 km 2 . The following oil and gas fields, Fulaerji and Taobao oil field, Pingyang oil and gas field, Tumuji oil sand, Alaxin, Erzhan and Baiyinnuole gas field, have been found early or later since 1960s. Saertu and Gaotaozi oil beds are main target strata and the type of oil and gas fields belongs to lithological and structure lithological character. The western slope oils have the characteristics of relatively low density, middle viscosity, richness in non hydrocarbon and low content of asphalt. The analysis of GC and GC MS shows the biodegradation and the feature of multiple filling of oil. The 25 norhopane series are absent in the biodegraded oils from all oil fields of western slope, including the Tumuji oil sand. The carbonate isotopic values of western slope oils are -29‰～-32‰, that of kerogen are -22‰～-24‰ of Jurassic coal rock and are -27‰～-31‰ of Qingshankou and Nenjiang mudstone. The maturity degree of source rocks of the western slope is very low, the calculated R o value of western slope oils are 0.75‰～0.95% based on the index of methyl phenanthrene and methyl dibenzene thiophene. So, the source rocks of western slope oils are mainly the Qingshankou lacustrine mudstone of central depression. The K Ar chronology data of reservoir bed authigenic illite of four wells, that is well Ta 20, Du 66, Fu 42 and Lai 24, is 56Ma, 45Ma, 35Ma and 35Ma respectively and the above well location is from east to west successively. So, the migrating period of the western slope oil is three stages at least.
The western slope of Songliao Basin spans two oil areas of Daqing and Jilin and its prospecting area is about 4.3×10 4 km 2 . The following oil and gas fields, Fulaerji and Taobao oil field, Pingyang oil and gas field, Tumuji oil sand, Alaxin, Erzhan and Baiyinnuole gas field, have been found early or later since 1960s. Saertu and Gaotaozi oil beds are main target strata and the type of oil and gas fields belongs to lithological and structure lithological character. The western slope oils have the characteristics of relatively low density, middle viscosity, richness in non hydrocarbon and low content of asphalt. The analysis of GC and GC MS shows the biodegradation and the feature of multiple filling of oil. The 25 norhopane series are absent in the biodegraded oils from all oil fields of western slope, including the Tumuji oil sand. The carbonate isotopic values of western slope oils are -29‰～-32‰, that of kerogen are -22‰～-24‰ of Jurassic coal rock and are -27‰～-31‰ of Qingshankou and Nenjiang mudstone. The maturity degree of source rocks of the western slope is very low, the calculated R o value of western slope oils are 0.75‰～0.95% based on the index of methyl phenanthrene and methyl dibenzene thiophene. So, the source rocks of western slope oils are mainly the Qingshankou lacustrine mudstone of central depression. The K Ar chronology data of reservoir bed authigenic illite of four wells, that is well Ta 20, Du 66, Fu 42 and Lai 24, is 56Ma, 45Ma, 35Ma and 35Ma respectively and the above well location is from east to west successively. So, the migrating period of the western slope oil is three stages at least.
2004, 22(4): 711-717.
Abstract:
A new method is developed to determine aliphatic content of kerogen using quantitative Fourier transform infrared spectra. The method uses micritic paraffin as reference standards, which consist of pure aliphatic chains. To discuss the experimental factors that may influence the result, different concentration of kerogen sample and fixed concentration of sample mixing with rock detriments or silicon mineral are analyzed respectively. The results indicate that the mixing minerals and rocks have little influence on the analytical results, in while high concentration of kerogens have much influence and should not exceed 3.5 mg when preparing the sample. So the quantitative method is reproducible, accurate and reliable. The simulating experiment is an important method in studying the evolution of organic matter, while studying natural evolving section is another. So kerogens in simulated samples and natural evolving samples in Dongying Depression are analyzed according to our quantitative method. After comparing the aliphatic contents of kerogens with different organic matter types, maturities and potentials of hydrocarbon, the author conclude that the aliphatic content obtained by FT IR can be a new index for evaluating hydrocarbon source rocks. The aliphatic content is determined by kerogen type under low maturity. The aliphatic contents often are higher than 20% in type Ⅰ kerogens, from 5% to 20% in type Ⅱ kerogens and below 5% in type Ⅲ kerogens, but with the same kerogen type the aliphatic content is determined by maturity. In low maturity the aliphatic content doesn't transform apparently, while in “oil window” the aliphatic content decrease faster and the aliphatic content will be near to naught over the "oil window". The relationship between aliphatic content and hydrocarbon/Toc indicated that the simulating and natural samples followed a slightly different evolving path if comparing the aliphatic content with the chroloform "A".
A new method is developed to determine aliphatic content of kerogen using quantitative Fourier transform infrared spectra. The method uses micritic paraffin as reference standards, which consist of pure aliphatic chains. To discuss the experimental factors that may influence the result, different concentration of kerogen sample and fixed concentration of sample mixing with rock detriments or silicon mineral are analyzed respectively. The results indicate that the mixing minerals and rocks have little influence on the analytical results, in while high concentration of kerogens have much influence and should not exceed 3.5 mg when preparing the sample. So the quantitative method is reproducible, accurate and reliable. The simulating experiment is an important method in studying the evolution of organic matter, while studying natural evolving section is another. So kerogens in simulated samples and natural evolving samples in Dongying Depression are analyzed according to our quantitative method. After comparing the aliphatic contents of kerogens with different organic matter types, maturities and potentials of hydrocarbon, the author conclude that the aliphatic content obtained by FT IR can be a new index for evaluating hydrocarbon source rocks. The aliphatic content is determined by kerogen type under low maturity. The aliphatic contents often are higher than 20% in type Ⅰ kerogens, from 5% to 20% in type Ⅱ kerogens and below 5% in type Ⅲ kerogens, but with the same kerogen type the aliphatic content is determined by maturity. In low maturity the aliphatic content doesn't transform apparently, while in “oil window” the aliphatic content decrease faster and the aliphatic content will be near to naught over the "oil window". The relationship between aliphatic content and hydrocarbon/Toc indicated that the simulating and natural samples followed a slightly different evolving path if comparing the aliphatic content with the chroloform "A".
2004, 22(4): 724-728.
Abstract:
A low mature coal (VRr=0.6%, from Manjia'er Depression, Tarim Basin, China in Jurassic system) was subjected to the closed system pyrolysis, in sealed gold tubes, under isothermal temperature conditions, ranging from 250 to 550 ℃ at temperature intervals of 50 ℃ (72 hours). The result shows that the biomarker compositions of the coal rock are dominated not only by mother matters, but also by coal mature and its lithology. This phenomenon is influenced by the intension of the different amount carbon biomarker, which was charged from mother matters of biomarker in generating hydrocarbon rocks at different evolution stages. At the same time, OEP cannot be regarded as a useful guideline of maturity in the thermal evolution of generating hydrocarbon rocks. The peak type of n alkenes presents two peaks in the whole evolution, in which the front peak is mainly mustered from nC 16 to nC 18, but the back peak is increasing while the simulated temperature rises. ΣC 21-/ΣC 22 + of coal rock shows regular changes with the temperature. The Pr/Ph ratio of coal rock falls when the temperature rises from 250℃to 550℃。
A low mature coal (VRr=0.6%, from Manjia'er Depression, Tarim Basin, China in Jurassic system) was subjected to the closed system pyrolysis, in sealed gold tubes, under isothermal temperature conditions, ranging from 250 to 550 ℃ at temperature intervals of 50 ℃ (72 hours). The result shows that the biomarker compositions of the coal rock are dominated not only by mother matters, but also by coal mature and its lithology. This phenomenon is influenced by the intension of the different amount carbon biomarker, which was charged from mother matters of biomarker in generating hydrocarbon rocks at different evolution stages. At the same time, OEP cannot be regarded as a useful guideline of maturity in the thermal evolution of generating hydrocarbon rocks. The peak type of n alkenes presents two peaks in the whole evolution, in which the front peak is mainly mustered from nC 16 to nC 18, but the back peak is increasing while the simulated temperature rises. ΣC 21-/ΣC 22 + of coal rock shows regular changes with the temperature. The Pr/Ph ratio of coal rock falls when the temperature rises from 250℃to 550℃。
2004, 22(4): 737-742.
Abstract:
Overpressure developed in Banqiao Sag, Eastern China, and obvious overpressure retardation of organic matter maturation was found in Well BS35. Such an organic matter maturity anomaly is distinctly different from those caused by variation in activation energies, conductivity contrasts, and hydrologic effects. Overpressure retardation has been proven to be conditional through integrated organic geochemical and geologic research, early developed overpressure, high original TOC contents of source rocks and the retention of the pore fluids (including products of organic matter maturation reactions) in the source rocks are three important factors affecting overpressure retardation of organic matter maturation, and overpressure retardation of organic matter maturation is quite important for clearly understanding petroleum exploration during deep burial in overpressured sedimentary basins.
Overpressure developed in Banqiao Sag, Eastern China, and obvious overpressure retardation of organic matter maturation was found in Well BS35. Such an organic matter maturity anomaly is distinctly different from those caused by variation in activation energies, conductivity contrasts, and hydrologic effects. Overpressure retardation has been proven to be conditional through integrated organic geochemical and geologic research, early developed overpressure, high original TOC contents of source rocks and the retention of the pore fluids (including products of organic matter maturation reactions) in the source rocks are three important factors affecting overpressure retardation of organic matter maturation, and overpressure retardation of organic matter maturation is quite important for clearly understanding petroleum exploration during deep burial in overpressured sedimentary basins.
