Objective A total of 820 million tons of potash reserves are predicted to exist in the Palaeocene–Eocene of the Jianghan Basin.However,the basin history is still unclear concerning the potash enriching conditions and...Objective A total of 820 million tons of potash reserves are predicted to exist in the Palaeocene–Eocene of the Jianghan Basin.However,the basin history is still unclear concerning the potash enriching conditions and mechanism.The Well SKD1 is the first exploration well drilled in the Paleogene of Jianghan Basin with continuous coring,which was implemented in the展开更多
This paper reports our primary effort in the quantitative reconstruction of paleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphic pollen records. The Eocene pollen data co...This paper reports our primary effort in the quantitative reconstruction of paleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphic pollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in the Jianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate in the Middle Eocene in the Jianghan basin was more or less comparable with that of the present 22°-26°N, characteristic of a humid, semi humid central southern subtropical climate. The annual temperature at that time dropped by 1 ℃-4 ℃ in the Late Eocene, approximately equal to that of the present 23°-28°N of northern central subtropical climate. However, the climate composite at that time, characterized by higher temperature, small annual range and big fluctuation in precipitation, was quite different from the present one. The average temperature in January in the Middle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect of winter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionally in the Late Eocene. Major temperature decline is recognized at the depth of 2 100 m in the borehole, as was indicated by the decline in average January temperature, the increase in annual range, and the increase in the deciduous broad leaved types of trees in the spore pollen assemblage. The sharp fluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for the migration and accumulation of salty deposit. When the precipitation was lower than 1 000 mm, ephemera shrub increased at the same depth as that of the salty deposit. It is, therefore, deduced that the formation of the salty deposit was attributed mainly to the dry and hot environment in the high mountains and deep basins. The small annual precipitation and the intense fluctuation are favorable for the sustainable accumulation of the salts, which is different from the present salty accumulation in the Northwest China.展开更多
The Yangtze River is one of the most important components of the East Asia river system.In this study,sediments in the Jianghan Basin,middle Yangtze River,were selected for trace element and rare earth element(REE)mea...The Yangtze River is one of the most important components of the East Asia river system.In this study,sediments in the Jianghan Basin,middle Yangtze River,were selected for trace element and rare earth element(REE)measurements,in order to decipher information on the change of sediment provenance and evolution of the Yangtze River.According to the elemental variations,the late Cenozoic sediments of the Jianghan Basin could be divided into four parts.During 2.68e2.28 Ma and 1.25e0 Ma,provenance of the sediments was consistent,whereas sediments were derived from variable sources during2.28e1.25 Ma.Comparison of the elemental compositions between the Pliocene and Quaternary sediments revealed a change in sediment source from a more felsic source area to a more basic source area around the PlioceneeQuaternary boundary.Input from the Emeishan LIP should account for this provenance change.Based on the provenance analysis of sediments in the Jianghan Basin,we infer that the Yangtze River developed into a large river with its drainage basin extended to the Emeishan LIP no later than the PlioceneeQuaternary boundary.展开更多
In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic...In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones include the dissolution of detrital K\|feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements, and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred in early, intermediate and late stages, based on the burial depth. The kinetics of fluid\|mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated numerically for these lacustrine sandstones, using a quasi\|stationary state approximation that incorporates simultaneous chemical reactions in a time\|space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution of K\|feldspar and albite and, therefore, led to the release of K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) into the diagenetic fluid. The increased K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the intermediate diagenetic stage the concentration of H\++ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K\|feldspar and albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline, K\|feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m, the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the precipitation of albite and the dissolution of quartz. The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs .展开更多
This study focuses on the thermodynamics of diagenetic fluid from the Eogene Xingouzui Formation which represents the most important reservoir in Field Oil T in the Jianghan Basin. The measured homogenization temperat...This study focuses on the thermodynamics of diagenetic fluid from the Eogene Xingouzui Formation which represents the most important reservoir in Field Oil T in the Jianghan Basin. The measured homogenization temperatures (110-139℃) of fiuld inclusions in diagenetic minerals fall within the range of 67- 155℃ at the middle diagehetic stage. The pressure of diagenetic fluid is estimated at 10.2-56 MPa. The activity of ions in the fluid shows a tendency of Ca2+ > Mg2+ > Na+ > K+ > Fe3+ > Fe2+ for cations, and HCO3 > SO4- > F- > Cl- >CO2-3 for anions. For the gaseous facies, there is a tendency of CO2> CO> H2S>CH4> H2. According to the thermodynamic calculations, the pH and Eh of the fluld are 5. 86 - 6. 47 and -0.73-0.64V,respectively. As a result of the interaction between such a diagenetic fluid and minerals in the sediments, feldspars were dissolved or alterated by other minerals. The clay mineral kaolinite was instable and hence was replaced by illite and chloritoid.展开更多
The amount of shale oil and its characterization are key issues in the study of shale oil.At present,many scholars use a variety of methods to evaluate the amount of shale oil,and use the calculated amount of hydrocar...The amount of shale oil and its characterization are key issues in the study of shale oil.At present,many scholars use a variety of methods to evaluate the amount of shale oil,and use the calculated amount of hydrocarbons to analyze its influencing factors;however,there is lack of detailed research on the storage space for shale-oil and it’s influencing factors.In view of this issue,gas chromatography(GC),gas chromatography-mass spectrometry(GC-MS),soxhlet extraction(SE),fieldemission scanning electron microscopy(FE-SEM),low-temperature nitrogen adsorption(LTNA),highpressure mercury intrusion(HPMI),and X-ray diffraction(XRD)were used to analyze and compare samples from two wells located in different deposition locations.The unconventional Well BYY2 and BX7 s were drilled in the depocenter and distal area of the Qianjiang Formation,respectively.Controlled by differences in the organic matter type and sedimentary environment,the organic matter in Well BYY2,which was found to be characterized by laminar shale,mainly originated from aquatic algae.The results showed that as the total organic carbon(TOC)content increased,the amount of shaleoil in the pores increased.Shale-oil was mostly stored in mesopores and macropores that had been preserved by dolomite minerals of a biogenic origin and also occurred in pores sized 5–200 nm and>1μm.Dolomite minerals of a biogenic origin and clay minerals contributed to the occurrence of shaleoil.In comparison,the organic matter in Well BX7 has been greatly influenced by terrestrial organic matter.Pores in the massive mudstones from Well BX7 were determined to be mainly mesopores preserved by clay minerals and quartz,and the shale-oil was mostly stored within the pores of<40 nm.When the TOC content was~2.5 wt.%,the generated shale-oil reached saturation.Clay minerals contributed to the occurrence of shale-oil,whereas quartz only contributed to the occurrence of shale-oil in macropores.展开更多
The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4 700-m-thick lacustrine succession, containing 1 800 m of halite deposits. The maximum thickness of the forma...The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4 700-m-thick lacustrine succession, containing 1 800 m of halite deposits. The maximum thickness of the formation is 4 700 m, and includes 1 800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. Depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth's orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.展开更多
The present geothermal gradient and terrestrial heat flow was calculated of 18 wells in the Jianghan Basin.Thermal gradient distribution of the Jianghan Basin was obtained based on data of systematical steady-state te...The present geothermal gradient and terrestrial heat flow was calculated of 18 wells in the Jianghan Basin.Thermal gradient distribution of the Jianghan Basin was obtained based on data of systematical steady-state temperature and oil-test temperature.The basin-wide average thermal gradient in depth interval of 0-4000 m is 33.59℃/km.We report nine measured terrestrial heat flow values based on the data of detailed thermal conductivity and systematical steady-state temperature.These values vary from 41.9 to 60.9 mW/m 2 with a mean of 52.3±6.3 mW/m 2.However,thermal history analyses based on vitrinite reflectance(VR) and apatite fission track(AFT) data indicate that thermal gradient in the northern and southern Qianbei Fault reached its peak of ~36 and ~39℃/km respectively in the Middle Jurassic and the Oligocene,and it descended during the early Miocene to the present-time value.Furthermore,tectonic subsidence analysis reveals that the tectonic subsidence of the Jianghan Basin in the Cretaceous to early Miocene was characterized by synrift initial subsidence followed by the subsequent thermal subsidence.The thermal history and tectonic subsidence history of Jianghan Basin are of great significance to petroleum exploration and hydrocarbon source assessment,because they bear directly on issues of petroleum source rock maturation.Based on the thermal history and tectonic subsidence history,with the combination of geochemical and thermal parameters,the maturation and the hydrocarbon generation intensity evolution history of the P2d source rocks are modeled.The results show that the P2d source rocks are in a higher degree of maturation at present,and the Yuan'an and Herong sags are the two most important kitchens in the Late Jurassic,Xiaoban Sag is another most important kitchen during the Late Cretaceous to late Paleogene,and the Zhijiang and Mianyang sags are other two important hydrocarbon kitchens in the Late Cretaceous.The Mianyang Sag and Yichang Ramp are the favorable exploration targets in the future.This study may provide new insight for the understanding of the oil and gas exploration potential for the Jianghan Basin.展开更多
基金the National Science Foundation of China(Grants No.41502089,41302059 and 41202059)for their financial support
文摘Objective A total of 820 million tons of potash reserves are predicted to exist in the Palaeocene–Eocene of the Jianghan Basin.However,the basin history is still unclear concerning the potash enriching conditions and mechanism.The Well SKD1 is the first exploration well drilled in the Paleogene of Jianghan Basin with continuous coring,which was implemented in the
文摘This paper reports our primary effort in the quantitative reconstruction of paleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphic pollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in the Jianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate in the Middle Eocene in the Jianghan basin was more or less comparable with that of the present 22°-26°N, characteristic of a humid, semi humid central southern subtropical climate. The annual temperature at that time dropped by 1 ℃-4 ℃ in the Late Eocene, approximately equal to that of the present 23°-28°N of northern central subtropical climate. However, the climate composite at that time, characterized by higher temperature, small annual range and big fluctuation in precipitation, was quite different from the present one. The average temperature in January in the Middle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect of winter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionally in the Late Eocene. Major temperature decline is recognized at the depth of 2 100 m in the borehole, as was indicated by the decline in average January temperature, the increase in annual range, and the increase in the deciduous broad leaved types of trees in the spore pollen assemblage. The sharp fluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for the migration and accumulation of salty deposit. When the precipitation was lower than 1 000 mm, ephemera shrub increased at the same depth as that of the salty deposit. It is, therefore, deduced that the formation of the salty deposit was attributed mainly to the dry and hot environment in the high mountains and deep basins. The small annual precipitation and the intense fluctuation are favorable for the sustainable accumulation of the salts, which is different from the present salty accumulation in the Northwest China.
基金supported by the National Natural Science Foundation of China(Grants Nos.40971008 and 40771213)the Open Research Program of State Key Laboratory of Loess and Quaternary Geology(Grant No.SKLLQG0908)
文摘The Yangtze River is one of the most important components of the East Asia river system.In this study,sediments in the Jianghan Basin,middle Yangtze River,were selected for trace element and rare earth element(REE)measurements,in order to decipher information on the change of sediment provenance and evolution of the Yangtze River.According to the elemental variations,the late Cenozoic sediments of the Jianghan Basin could be divided into four parts.During 2.68e2.28 Ma and 1.25e0 Ma,provenance of the sediments was consistent,whereas sediments were derived from variable sources during2.28e1.25 Ma.Comparison of the elemental compositions between the Pliocene and Quaternary sediments revealed a change in sediment source from a more felsic source area to a more basic source area around the PlioceneeQuaternary boundary.Input from the Emeishan LIP should account for this provenance change.Based on the provenance analysis of sediments in the Jianghan Basin,we infer that the Yangtze River developed into a large river with its drainage basin extended to the Emeishan LIP no later than the PlioceneeQuaternary boundary.
基金This project was funded by the National Natural science Foundation of China (GrantNo .4 91 330 80 ) and by the Trans centuryTraining Program me Foudation for the Talentssponsored by the State Education Commission of China
文摘In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones include the dissolution of detrital K\|feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements, and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred in early, intermediate and late stages, based on the burial depth. The kinetics of fluid\|mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated numerically for these lacustrine sandstones, using a quasi\|stationary state approximation that incorporates simultaneous chemical reactions in a time\|space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution of K\|feldspar and albite and, therefore, led to the release of K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) into the diagenetic fluid. The increased K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the intermediate diagenetic stage the concentration of H\++ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K\|feldspar and albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline, K\|feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m, the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the precipitation of albite and the dissolution of quartz. The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs .
文摘This study focuses on the thermodynamics of diagenetic fluid from the Eogene Xingouzui Formation which represents the most important reservoir in Field Oil T in the Jianghan Basin. The measured homogenization temperatures (110-139℃) of fiuld inclusions in diagenetic minerals fall within the range of 67- 155℃ at the middle diagehetic stage. The pressure of diagenetic fluid is estimated at 10.2-56 MPa. The activity of ions in the fluid shows a tendency of Ca2+ > Mg2+ > Na+ > K+ > Fe3+ > Fe2+ for cations, and HCO3 > SO4- > F- > Cl- >CO2-3 for anions. For the gaseous facies, there is a tendency of CO2> CO> H2S>CH4> H2. According to the thermodynamic calculations, the pH and Eh of the fluld are 5. 86 - 6. 47 and -0.73-0.64V,respectively. As a result of the interaction between such a diagenetic fluid and minerals in the sediments, feldspars were dissolved or alterated by other minerals. The clay mineral kaolinite was instable and hence was replaced by illite and chloritoid.
基金financially supported by the National Science Foundation of China(Nos.41830431,41672139)thirteenth research plan of the Ministry of Science and Technology of China(Nos.2017ZX05049005-007,2016ZX05034002-003)。
文摘The amount of shale oil and its characterization are key issues in the study of shale oil.At present,many scholars use a variety of methods to evaluate the amount of shale oil,and use the calculated amount of hydrocarbons to analyze its influencing factors;however,there is lack of detailed research on the storage space for shale-oil and it’s influencing factors.In view of this issue,gas chromatography(GC),gas chromatography-mass spectrometry(GC-MS),soxhlet extraction(SE),fieldemission scanning electron microscopy(FE-SEM),low-temperature nitrogen adsorption(LTNA),highpressure mercury intrusion(HPMI),and X-ray diffraction(XRD)were used to analyze and compare samples from two wells located in different deposition locations.The unconventional Well BYY2 and BX7 s were drilled in the depocenter and distal area of the Qianjiang Formation,respectively.Controlled by differences in the organic matter type and sedimentary environment,the organic matter in Well BYY2,which was found to be characterized by laminar shale,mainly originated from aquatic algae.The results showed that as the total organic carbon(TOC)content increased,the amount of shaleoil in the pores increased.Shale-oil was mostly stored in mesopores and macropores that had been preserved by dolomite minerals of a biogenic origin and also occurred in pores sized 5–200 nm and>1μm.Dolomite minerals of a biogenic origin and clay minerals contributed to the occurrence of shaleoil.In comparison,the organic matter in Well BX7 has been greatly influenced by terrestrial organic matter.Pores in the massive mudstones from Well BX7 were determined to be mainly mesopores preserved by clay minerals and quartz,and the shale-oil was mostly stored within the pores of<40 nm.When the TOC content was~2.5 wt.%,the generated shale-oil reached saturation.Clay minerals contributed to the occurrence of shale-oil,whereas quartz only contributed to the occurrence of shale-oil in macropores.
基金supported by the National Natural Science Foundation of China (No. 41322013)the Program for New Century Excellent Talents in Universities (No. NCET-110723)+2 种基金the National Key Basic Research Development Program of China (No. 2012CB822003)the Programme of Introducing Talents of Discipline to Universities (No. B14031)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (No. CUG110611)
文摘The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4 700-m-thick lacustrine succession, containing 1 800 m of halite deposits. The maximum thickness of the formation is 4 700 m, and includes 1 800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. Depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth's orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.
基金supported by National Natural Science Foundation of China(Grant No.41102152)Sinopec Marine Prospective Study Program(Grant No.2007CB411704)
文摘The present geothermal gradient and terrestrial heat flow was calculated of 18 wells in the Jianghan Basin.Thermal gradient distribution of the Jianghan Basin was obtained based on data of systematical steady-state temperature and oil-test temperature.The basin-wide average thermal gradient in depth interval of 0-4000 m is 33.59℃/km.We report nine measured terrestrial heat flow values based on the data of detailed thermal conductivity and systematical steady-state temperature.These values vary from 41.9 to 60.9 mW/m 2 with a mean of 52.3±6.3 mW/m 2.However,thermal history analyses based on vitrinite reflectance(VR) and apatite fission track(AFT) data indicate that thermal gradient in the northern and southern Qianbei Fault reached its peak of ~36 and ~39℃/km respectively in the Middle Jurassic and the Oligocene,and it descended during the early Miocene to the present-time value.Furthermore,tectonic subsidence analysis reveals that the tectonic subsidence of the Jianghan Basin in the Cretaceous to early Miocene was characterized by synrift initial subsidence followed by the subsequent thermal subsidence.The thermal history and tectonic subsidence history of Jianghan Basin are of great significance to petroleum exploration and hydrocarbon source assessment,because they bear directly on issues of petroleum source rock maturation.Based on the thermal history and tectonic subsidence history,with the combination of geochemical and thermal parameters,the maturation and the hydrocarbon generation intensity evolution history of the P2d source rocks are modeled.The results show that the P2d source rocks are in a higher degree of maturation at present,and the Yuan'an and Herong sags are the two most important kitchens in the Late Jurassic,Xiaoban Sag is another most important kitchen during the Late Cretaceous to late Paleogene,and the Zhijiang and Mianyang sags are other two important hydrocarbon kitchens in the Late Cretaceous.The Mianyang Sag and Yichang Ramp are the favorable exploration targets in the future.This study may provide new insight for the understanding of the oil and gas exploration potential for the Jianghan Basin.