Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteris...Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteristics of the Lower Member,Middle Member,and Upper Member were analyzed and classified.Before the use of carbon,oxygen,and strontium isotopes in the analysis,all of the geochemical data were tested for validity.On the basis of the Z values obtained from carbon and oxygen isotopes,the paleoenvironments of the three members were elucidated.Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea.Middle Member developed in a semi-enclosed to normal marine environment with many rivers.Upper Member was formed in a normal marine environment.The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation,forming a relatively enclosed depositional setting.Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks;these paleogullies can be identified.On the basis of a comprehensive analysis,we propose that the Huanglong Formation developed in a platform system.Four microfacies were identified：supratidal flat,dolostone flat,grain shoal,and shelf microfacies.The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation,while the supratidal flat and shelf microfacies developed very few high-quality reservoirs.The paleogullies,in which increased amounts of grain shoal microfacies developed,controlled the distribution of high-quality reservoirs.展开更多
Based on a comprehensive study of texture,diagenetic behavior and evolution of dolomite in the Huanglong Formation,trace （e.g.,Fe,Mn and Sr） and rare earth element （REE） geochemistry,andisotopic characteristics （...Based on a comprehensive study of texture,diagenetic behavior and evolution of dolomite in the Huanglong Formation,trace （e.g.,Fe,Mn and Sr） and rare earth element （REE） geochemistry,andisotopic characteristics （e.g.,C,O and Sr）,four types of diagenetic fluids are identified in the Huanglong Formation dolomite reservoirs of the Eastern Sichuan Basin,China：1）：marine-derived pore waters in the marine diagenetic environment,2） sabkha compaction brine conserved in the early shallowburied diagenetic environment,3） strongly-oxidizing low-temperature meteoric water in the seepagesubsurface flow diagenetic environment,and 4） strongly reducing deeply seated mixed hot brine in the middle and deep burial diagenetic environment.The fluids developed hereditarily from one environment to another,which resulted in its respective characteristics.Fluid characteristics play an important role in the development of dolomite reservoirs：1） dolomitization by marine-derived pore water in the quasisyngenetic stage did not form an effective reservoir; 2） early diagenetic burial dolomitization by the sabkha compaction brine formed the basis for reservoir development; 3） meteoric water karstification in the paleo-epidiagenetic stage expanded both the distribution and the size of the reservoirs,and improved the reservoir quality; 4） deep-burial dissolution and tectonic fracturing in the reburial diagenetic stage further improved reservoir porosity and permeability.展开更多
Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely co...Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely corroded and replaced secondary calcic karstic rocks. The carbon, oxygen and strontium isotope compositions of the various karst rocks are analyzed systematically and compared to rocks without karst corrosion. The results indicate that（1） the Huanglong Formation in the eastern Sichuan Basin was a restricted bay supplied and controlled by freshwater in which mudmicrite and mud-dolomicrite exhibit low δ13C and δ18O values and high 87Sr/86 Sr ratios;（2） all types of karstic rocks in the paleokarst reservoirs of the Huanglong Formation in the research area are affected by atmospheric freshwater with the δ13C and δ18O values and 87Sr/86 Sr ratios in the original formation approaching those of atmospheric freshwater, which reflects ancient hydrological conditions, fluid properties, isotopic source and the fractionation effect;（3） the intensely corroded and replaced secondary limestone is affected by a variety of diagenetic fluids, often reflected by δ13C and δ18O values, while the 87Sr/86 Sr ratios exhibit the strong degree of the corrosion;（4） after comparing the 87Sr/86 Sr ratios of each type of karst rock, the diagenetic fluids are determined to be mainly atmospheric freshwater, and depending on the strength of corrosion, and the low 87Sr/86 Sr ratio fluids in the layer will participate in the karst process. The carbon, oxygen, and strontium isotopes of different karstic reservoirs can provide meaningful geochemical information for forecasting and evaluating the development and distribution rules of the Huanglong Formation at the margin of the eastern Sichuan Basin in time and space.展开更多
Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbon...Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.展开更多
基金granted by the National Science and Technology Major Project(2011ZX05004-001)
文摘Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteristics of the Lower Member,Middle Member,and Upper Member were analyzed and classified.Before the use of carbon,oxygen,and strontium isotopes in the analysis,all of the geochemical data were tested for validity.On the basis of the Z values obtained from carbon and oxygen isotopes,the paleoenvironments of the three members were elucidated.Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea.Middle Member developed in a semi-enclosed to normal marine environment with many rivers.Upper Member was formed in a normal marine environment.The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation,forming a relatively enclosed depositional setting.Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks;these paleogullies can be identified.On the basis of a comprehensive analysis,we propose that the Huanglong Formation developed in a platform system.Four microfacies were identified：supratidal flat,dolostone flat,grain shoal,and shelf microfacies.The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation,while the supratidal flat and shelf microfacies developed very few high-quality reservoirs.The paleogullies,in which increased amounts of grain shoal microfacies developed,controlled the distribution of high-quality reservoirs.
基金supported by the National Natural Science Foundation of China(Grant No.41002033)National Major Science and Technology Specific Project of China(2011ZX05030-003-02)+1 种基金Natural Science Key Project of Education Department in Sichuan(13ZA0058)Foundation for Fostering Middle-aged and Young Key Teachers of Chengdu University of Technology
文摘Based on a comprehensive study of texture,diagenetic behavior and evolution of dolomite in the Huanglong Formation,trace （e.g.,Fe,Mn and Sr） and rare earth element （REE） geochemistry,andisotopic characteristics （e.g.,C,O and Sr）,four types of diagenetic fluids are identified in the Huanglong Formation dolomite reservoirs of the Eastern Sichuan Basin,China：1）：marine-derived pore waters in the marine diagenetic environment,2） sabkha compaction brine conserved in the early shallowburied diagenetic environment,3） strongly-oxidizing low-temperature meteoric water in the seepagesubsurface flow diagenetic environment,and 4） strongly reducing deeply seated mixed hot brine in the middle and deep burial diagenetic environment.The fluids developed hereditarily from one environment to another,which resulted in its respective characteristics.Fluid characteristics play an important role in the development of dolomite reservoirs：1） dolomitization by marine-derived pore water in the quasisyngenetic stage did not form an effective reservoir; 2） early diagenetic burial dolomitization by the sabkha compaction brine formed the basis for reservoir development; 3） meteoric water karstification in the paleo-epidiagenetic stage expanded both the distribution and the size of the reservoirs,and improved the reservoir quality; 4） deep-burial dissolution and tectonic fracturing in the reburial diagenetic stage further improved reservoir porosity and permeability.
基金supported by the National Major Science of China (Grant NO. 2011ZX05030-003-002)Natural Science key project of Education Department in Sichuan (NO.13ZA0058)
文摘Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely corroded and replaced secondary calcic karstic rocks. The carbon, oxygen and strontium isotope compositions of the various karst rocks are analyzed systematically and compared to rocks without karst corrosion. The results indicate that（1） the Huanglong Formation in the eastern Sichuan Basin was a restricted bay supplied and controlled by freshwater in which mudmicrite and mud-dolomicrite exhibit low δ13C and δ18O values and high 87Sr/86 Sr ratios;（2） all types of karstic rocks in the paleokarst reservoirs of the Huanglong Formation in the research area are affected by atmospheric freshwater with the δ13C and δ18O values and 87Sr/86 Sr ratios in the original formation approaching those of atmospheric freshwater, which reflects ancient hydrological conditions, fluid properties, isotopic source and the fractionation effect;（3） the intensely corroded and replaced secondary limestone is affected by a variety of diagenetic fluids, often reflected by δ13C and δ18O values, while the 87Sr/86 Sr ratios exhibit the strong degree of the corrosion;（4） after comparing the 87Sr/86 Sr ratios of each type of karst rock, the diagenetic fluids are determined to be mainly atmospheric freshwater, and depending on the strength of corrosion, and the low 87Sr/86 Sr ratio fluids in the layer will participate in the karst process. The carbon, oxygen, and strontium isotopes of different karstic reservoirs can provide meaningful geochemical information for forecasting and evaluating the development and distribution rules of the Huanglong Formation at the margin of the eastern Sichuan Basin in time and space.
基金This study was supported by the project ofthe Science and Technology Innovation Fund of Command Center of Natural Resources Intergrated Survey entitled“Temporal and spatial distribution of paleochannel and origin of organic carbon burial in the Western Bohai Sea since 2.28Ma”(KC20220011)the project entitled“Characterization of Carboniferous-Early Permian heterogeneous porous carbonate reservoirs and hydrocarbon potential analysis in the central uplift of the South Yellow Sea Basin”(KLSG2304)+3 种基金by the Key laboratory of Submarine Science,Ministry of Natural Resources,the project entitled“1∶50000 Marine regional Geological survey in Caofeidian Sea Area,Bohai Sea”(ZD20220602)“1∶250000 Marine regional Geological survey in Weihai Sea Area,North Yellow Sea”(DD20230412)“Geological survey on tectonic and sedimentary conditions of Laoshan uplift”(DD2016015)by the China Geological Survey,and the project entitled“Study on Hydrocarbon Accumulation Failure and Fluid Evolution Reduction of the Permian Reservoir in the Laoshan Uplift,South Yellow Sea”(42076220)organized by the National Natural Science Foundation of China.
文摘Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.
