New total organic carbon （TOC） data from the two Ordovician-Silurian transitional graptolite-bearing black shale intervals, the Wufeng （五峰） Formation and the Longmaxi （龙马溪） Formation in Central Guizhou （...New total organic carbon （TOC） data from the two Ordovician-Silurian transitional graptolite-bearing black shale intervals, the Wufeng （五峰） Formation and the Longmaxi （龙马溪） Formation in Central Guizhou （贵州） and West Hubei （湖北）, respectively, as well as previously reported TOC data from the same intervals in other places on the Yangtze platform of South China, have been used to produce an initial estimate of the primary paleoproductivity via a conventional inverse method （i.e., Rpp.inverse）. The values of the Rpp.inverse are estimated to be 32 （43-21） gC/（m^2·a）（Wufeng Formation） and 21 （27-16） gC/（m^2·a） （Longmaxi Formation）. Also, simultaneously, the habitat types （i.e., HT; cf., BA： benthic assemblage） and their temporal and spatial changes have been documented from the same succession, and an initial estimate of the primary paleoproductivity has been produced using a forward method （i.e., Rpp-forward） Beingbounded mainly by the peritidal to inner-shelf environment shelly-facies or mixed-facies successions with BA1 to BA3 faunas both at the top and the base, which indicates the habitat types from HT Ⅱ to HT Ⅲ2, the biohabitat type of the two graptolite-bearing black shale intervals can be limited to HT III to HT IV, corresponding to the inner shelf to the outer shelf, with depths from roughly 60 m to 200-300 m. Based on the current data from the South China Sea and the southern part of the East China Sea, values of Rpp-forward should be about 100 to 400 gC/（m^2·a）. The difference in the results via the two methods suggests that paleoproductivity estimates from the geological strata need to be made cautiously, with particular attention paid to the paleogeographic setting, oxic-anoxic conditions, as also the preservation factor of organic carbon.展开更多
Geological conditions and main controlling factors of gas accumulation in subsalt Ma 4 Member of Ordovician Majiagou Formation are examined based on large amounts of drilling,logging and seismic data.The new understan...Geological conditions and main controlling factors of gas accumulation in subsalt Ma 4 Member of Ordovician Majiagou Formation are examined based on large amounts of drilling,logging and seismic data.The new understandings on the control of paleo-uplift over facies,reservoirs and accumulations are reached:(1)During the sedimentary period of Majiagou Formation,the central paleo-uplift divided the North China Sea in central-eastern of the basin from the Qinqi Sea at southwest margin of the basin,and controlled the deposition of the thick hummocky grain beach facies dolomite on platform margin of Ma 4 Member.Under the influence of the evolution of the central paleo-uplift,the frame of two uplifts alternate with two sags was formed in the central-eastern part of the basin,dolomite of inner-platform beach facies developed in the underwater low-uplift zones,and marl developed in the low-lying areas between uplifts.(2)From the central paleo-uplift to the east margin of the basin,the dolomite in the Ma 4 Member gradually becomes thinner and turns into limestone.The lateral sealing of the limestone sedimentary facies transition zone gives rise to a large dolomite lithological trap.(3)During the late Caledonian,the basin was uplifted as a whole,and the central paleo-uplift was exposed and denuded to various degrees;high-quality Upper Paleozoic Carboniferous-Permian coal measures source rocks deposited on the paleo-uplift in an area of 60000 km^(2),providing large-scale hydrocarbon for the dolomite lithological traps in the underlying Ma 4 Member.(4)During the Indosinian-Yanshanian stage,the basin tilted westwards,and central paleo-uplift depressed into an efficient hydrocarbon supply window.The gas from the Upper Paleozoic source rock migrated through the high porosity and permeability dolomite in the central paleo-uplift to and accumulated in the updip high part;meanwhile,the subsalt marine source rock supplied gas through the Caledonian faults and micro-fractures as a significant supplementary.Under the guidance of the above new understandings,two favorable exploration areas in the Ma 4 Member in the central-eastern basin were sorted out.Two risk exploration wells were deployed,both revealed thick gas-bearing layer in Ma 4 Member,and one of them tapped high production gas flow.The study has brought a historic breakthrough in the gas exploration of subsalt Ma 4 Member of Ordovician,and opened up a new frontier of gas exploration in the Ordos Basin.展开更多
A continuous Ordovician-Silurian boundary section from the upper Wufeng Formation through the Kuanyinchiao Formation to the lower Lungmachi Formation has been carefully measured and collected at Shuanghe of Changning,...A continuous Ordovician-Silurian boundary section from the upper Wufeng Formation through the Kuanyinchiao Formation to the lower Lungmachi Formation has been carefully measured and collected at Shuanghe of Changning, southern Sichuan Province. For the first time, the temporal changes of α- and β-diversities of the Hirnantia fauna have been discussed in great detail. The general trend of brachiopod diversity change, increasing upward, is consistent with the regional trend of the Yangtze Platform, which had been controlled by both intrinsic and extrinsic factors. However, the sudden drop of diversity for a short period in the upper Kuanyinchiao Formation might have been controlled by environmental factors rather than normal faunal turnover. Synecological analysis using numerical methods recognizes two brachiopod-dominated associations of the Hirnantia fauna, the Dalmanella-Kinnella Association and the Mirorthis Association, both living in an offshore, deeper water environment corresponding to BA3-upper BA4, particularly lower BA3.展开更多
Located northwest of the Jiangshan-Shaoxing Fault Zone,western and northwestern Zhejiang and northeastern Jiangxi provinces experienced major changes in bio-and litho-facies and paleogeography through the Ordovician-S...Located northwest of the Jiangshan-Shaoxing Fault Zone,western and northwestern Zhejiang and northeastern Jiangxi provinces experienced major changes in bio-and litho-facies and paleogeography through the Ordovician-Silurian transition (late Katian,Hirnantian,and early Rhuddanian),as manifested by stratigraphic,paleontologic and synecologic records.Three geographic units under consideration are South,Central,and North areas.The western margin of the South area was occupied by the Huaiyu Mountains,whereas the other two parts were covered by the Zhe-Gan Sea during late Katian (Late Ordovician) time.In the early stage of the Changwu Formation deposition (late Katian),the sea was deepening northeastward,but with shallower conditions in the southwest and deeper conditions in the northeast.During mid to late stages of Changwu Formation deposition (latest Katian),the sea became much shallower and the sea bottom was uplifted substantially,which occurred somewhat prior to the global trend.During the Hirnantian (latest Ordovician) and early Rhuddanian (earliest Silurian),the study region became a shallow bay under expansion of the Cathaysian Oldland.There occurred a major drop of sea level and great changes in benthic biota with the occurrence of many new immigrants through the Ordovician-Silurian transition,which are closely related to a unique regional orogeny.The Yangtze and Cathaysian blocks may have amalgamated within the South China Paleoplate during this interval to cause the continuous uplifting and northwestward expansion of the Cathaysian Oldland.展开更多
文章根据露头层序地层原理和方法,考虑层序关键界面、体系域特征、层序区域追踪对比性,对江南过渡带周边(石台—黟县一带)江南地层分区、江南过渡地层分区及下扬子地层分区奥陶系进行了露头层序地层研究。研究表明:江南过渡带周边奥陶...文章根据露头层序地层原理和方法,考虑层序关键界面、体系域特征、层序区域追踪对比性,对江南过渡带周边(石台—黟县一带)江南地层分区、江南过渡地层分区及下扬子地层分区奥陶系进行了露头层序地层研究。研究表明:江南过渡带周边奥陶系可识别出2个完整二级层序(SS1、SS2)与1个二级层序低水位体系域(SS3-LST)和11个三级层序(OSQ1～OSQ11),平均每个三级层序约为4.05 Ma,反映了研究区奥陶纪具有11次相对较大的海平面升降旋回;三级层序发育海侵体系域(transgressive system tract,TST)和高水位体系域(highstand system tract,HST),有时缺失低水位体系域(lowstand system tract,LST),局部凝缩段(condensed section,CS)难以识别;二级层序能进行较好的区域对比,三级层序不能完全对比;研究区北西高南东低,海水向北西方向持续海侵;北西侧灰质成分较高,水体相对较浅,而南东侧泥质成分较高,水体较深,在中间的江南过渡带,主体为斜坡相沉积,局部发育重力流沉积,其成因可能与江南断裂为同沉积断裂有较为密切的关系。展开更多
基金supported by the National Natural Science Foundation of China (Nos. 40372057, 40772076)the SINOPEC project (G0800-06-ZS-319)
文摘New total organic carbon （TOC） data from the two Ordovician-Silurian transitional graptolite-bearing black shale intervals, the Wufeng （五峰） Formation and the Longmaxi （龙马溪） Formation in Central Guizhou （贵州） and West Hubei （湖北）, respectively, as well as previously reported TOC data from the same intervals in other places on the Yangtze platform of South China, have been used to produce an initial estimate of the primary paleoproductivity via a conventional inverse method （i.e., Rpp.inverse）. The values of the Rpp.inverse are estimated to be 32 （43-21） gC/（m^2·a）（Wufeng Formation） and 21 （27-16） gC/（m^2·a） （Longmaxi Formation）. Also, simultaneously, the habitat types （i.e., HT; cf., BA： benthic assemblage） and their temporal and spatial changes have been documented from the same succession, and an initial estimate of the primary paleoproductivity has been produced using a forward method （i.e., Rpp-forward） Beingbounded mainly by the peritidal to inner-shelf environment shelly-facies or mixed-facies successions with BA1 to BA3 faunas both at the top and the base, which indicates the habitat types from HT Ⅱ to HT Ⅲ2, the biohabitat type of the two graptolite-bearing black shale intervals can be limited to HT III to HT IV, corresponding to the inner shelf to the outer shelf, with depths from roughly 60 m to 200-300 m. Based on the current data from the South China Sea and the southern part of the East China Sea, values of Rpp-forward should be about 100 to 400 gC/（m^2·a）. The difference in the results via the two methods suggests that paleoproductivity estimates from the geological strata need to be made cautiously, with particular attention paid to the paleogeographic setting, oxic-anoxic conditions, as also the preservation factor of organic carbon.
基金Supported by the Scientific Research and Technology Development Project of PetroChina。
文摘Geological conditions and main controlling factors of gas accumulation in subsalt Ma 4 Member of Ordovician Majiagou Formation are examined based on large amounts of drilling,logging and seismic data.The new understandings on the control of paleo-uplift over facies,reservoirs and accumulations are reached:(1)During the sedimentary period of Majiagou Formation,the central paleo-uplift divided the North China Sea in central-eastern of the basin from the Qinqi Sea at southwest margin of the basin,and controlled the deposition of the thick hummocky grain beach facies dolomite on platform margin of Ma 4 Member.Under the influence of the evolution of the central paleo-uplift,the frame of two uplifts alternate with two sags was formed in the central-eastern part of the basin,dolomite of inner-platform beach facies developed in the underwater low-uplift zones,and marl developed in the low-lying areas between uplifts.(2)From the central paleo-uplift to the east margin of the basin,the dolomite in the Ma 4 Member gradually becomes thinner and turns into limestone.The lateral sealing of the limestone sedimentary facies transition zone gives rise to a large dolomite lithological trap.(3)During the late Caledonian,the basin was uplifted as a whole,and the central paleo-uplift was exposed and denuded to various degrees;high-quality Upper Paleozoic Carboniferous-Permian coal measures source rocks deposited on the paleo-uplift in an area of 60000 km^(2),providing large-scale hydrocarbon for the dolomite lithological traps in the underlying Ma 4 Member.(4)During the Indosinian-Yanshanian stage,the basin tilted westwards,and central paleo-uplift depressed into an efficient hydrocarbon supply window.The gas from the Upper Paleozoic source rock migrated through the high porosity and permeability dolomite in the central paleo-uplift to and accumulated in the updip high part;meanwhile,the subsalt marine source rock supplied gas through the Caledonian faults and micro-fractures as a significant supplementary.Under the guidance of the above new understandings,two favorable exploration areas in the Ma 4 Member in the central-eastern basin were sorted out.Two risk exploration wells were deployed,both revealed thick gas-bearing layer in Ma 4 Member,and one of them tapped high production gas flow.The study has brought a historic breakthrough in the gas exploration of subsalt Ma 4 Member of Ordovician,and opened up a new frontier of gas exploration in the Ordos Basin.
基金supported by the Chinese Academy of Sciences (KZCX2-YW-Q05-01)the Ministry of Science and Technology of China (2006FY120300-5)the National Natural Science Foundation of China (40825006, 40972020), and the State Key Laboratory of Palaeobiology and Stratigraphy of NIGPAS
文摘A continuous Ordovician-Silurian boundary section from the upper Wufeng Formation through the Kuanyinchiao Formation to the lower Lungmachi Formation has been carefully measured and collected at Shuanghe of Changning, southern Sichuan Province. For the first time, the temporal changes of α- and β-diversities of the Hirnantia fauna have been discussed in great detail. The general trend of brachiopod diversity change, increasing upward, is consistent with the regional trend of the Yangtze Platform, which had been controlled by both intrinsic and extrinsic factors. However, the sudden drop of diversity for a short period in the upper Kuanyinchiao Formation might have been controlled by environmental factors rather than normal faunal turnover. Synecological analysis using numerical methods recognizes two brachiopod-dominated associations of the Hirnantia fauna, the Dalmanella-Kinnella Association and the Mirorthis Association, both living in an offshore, deeper water environment corresponding to BA3-upper BA4, particularly lower BA3.
基金supported by Chinese Academy of Sciences (Grant No.KZCX2-YW-Q05-01)National Natural Science Foundation of China(Grant No.40825006)+1 种基金Ministry of Science and Technology (Grant Nos.2006CB806402,2006 FY120300-5)Department of Land and Resources of Zhejiang (Grant No.200711)
文摘Located northwest of the Jiangshan-Shaoxing Fault Zone,western and northwestern Zhejiang and northeastern Jiangxi provinces experienced major changes in bio-and litho-facies and paleogeography through the Ordovician-Silurian transition (late Katian,Hirnantian,and early Rhuddanian),as manifested by stratigraphic,paleontologic and synecologic records.Three geographic units under consideration are South,Central,and North areas.The western margin of the South area was occupied by the Huaiyu Mountains,whereas the other two parts were covered by the Zhe-Gan Sea during late Katian (Late Ordovician) time.In the early stage of the Changwu Formation deposition (late Katian),the sea was deepening northeastward,but with shallower conditions in the southwest and deeper conditions in the northeast.During mid to late stages of Changwu Formation deposition (latest Katian),the sea became much shallower and the sea bottom was uplifted substantially,which occurred somewhat prior to the global trend.During the Hirnantian (latest Ordovician) and early Rhuddanian (earliest Silurian),the study region became a shallow bay under expansion of the Cathaysian Oldland.There occurred a major drop of sea level and great changes in benthic biota with the occurrence of many new immigrants through the Ordovician-Silurian transition,which are closely related to a unique regional orogeny.The Yangtze and Cathaysian blocks may have amalgamated within the South China Paleoplate during this interval to cause the continuous uplifting and northwestward expansion of the Cathaysian Oldland.
文摘文章根据露头层序地层原理和方法,考虑层序关键界面、体系域特征、层序区域追踪对比性,对江南过渡带周边(石台—黟县一带)江南地层分区、江南过渡地层分区及下扬子地层分区奥陶系进行了露头层序地层研究。研究表明:江南过渡带周边奥陶系可识别出2个完整二级层序(SS1、SS2)与1个二级层序低水位体系域(SS3-LST)和11个三级层序(OSQ1～OSQ11),平均每个三级层序约为4.05 Ma,反映了研究区奥陶纪具有11次相对较大的海平面升降旋回;三级层序发育海侵体系域(transgressive system tract,TST)和高水位体系域(highstand system tract,HST),有时缺失低水位体系域(lowstand system tract,LST),局部凝缩段(condensed section,CS)难以识别;二级层序能进行较好的区域对比,三级层序不能完全对比;研究区北西高南东低,海水向北西方向持续海侵;北西侧灰质成分较高,水体相对较浅,而南东侧泥质成分较高,水体较深,在中间的江南过渡带,主体为斜坡相沉积,局部发育重力流沉积,其成因可能与江南断裂为同沉积断裂有较为密切的关系。
