In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is belie...In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.展开更多
Study of dolomite texture can contribute to understanding the process of dolomitization.This research reports textures and homogenization temperatures of dolomites from the Permian-Triassic strata in the Sichuan Basin...Study of dolomite texture can contribute to understanding the process of dolomitization.This research reports textures and homogenization temperatures of dolomites from the Permian-Triassic strata in the Sichuan Basin and the Lower Paleozoic strata in the Tarim Basin,which provided insights into relationships between dolomite textures and their formation temperatures.Our results are summarized as follows：1） dolomites with well-preserved texture indicate low dolomitization temperature.However,in certain diagenetic environments,the hydrothermal dolomitization may completely or partially preserve the original texture of dolomites.2） The formation temperatures of non-planar dolomites are always higher than those of planar dolomites.3） The formation temperatures of dolomite cements are generally higher than those of replacive dolomites.4） Although the formation temperatures of saddle dolomite cements have a wide range,they show higher values than those of the planar subhedral to euhedral dolomite cements.Thus,saddle dolomites could generally be an indicator of high precipitation temperature.5） The fluid Mg/Ca ratio is another element controlling dolomite morphology.Micritic dolomites,which precipitate from hypersaline fluids with a high Mg/Ca ratio in a subaerial environment could also have features of non-planar anhedral crystal shape because of rapid nucleation and crystallization during dolomitization.展开更多
Mesozoic marine shale oil was found in the Qiangtang Basin by a large number of hydrocarbon geological surveys and shallow drilling sampling.Based on systematic observation and experimental analysis of outcrop and cor...Mesozoic marine shale oil was found in the Qiangtang Basin by a large number of hydrocarbon geological surveys and shallow drilling sampling.Based on systematic observation and experimental analysis of outcrop and core samples,the deposition and development conditions and characteristics of marine shale are revealed,the geochemical and reservoir characteristics of marine shale are evaluated,and the layers of marine shale oil in the Mesozoic are determined.The following geological understandings are obtained.First,there are two sets of marine organic-rich shales,the Lower Jurassic Quse Formation and the Upper Triassic Bagong Formation,in the Qiangtang Basin.They are mainly composed of laminated shale with massive mudstone.The laminated organic-rich shale of the Quse Formation is located in the lower part of the stratum,with a thickness of 50–75 m,and mainly distributed in southern Qiangtang Basin and the central-west of northern Qiangtang Basin.The laminated organic-rich shale of the Bagong Formation is located in the middle of the stratum,with a thickness of 250–350 m,and distributed in both northern and southern Qiangtang Basin.Second,the two sets of laminated organic-rich shales develop foliation,and various types of micropores and microfractures.The average content of brittle minerals is 70%,implying a high fracturability.The average porosity is 5.89%,indicating good reservoir physical properties to the level of moderate–good shale oil reservoirs.Third,the organic-rich shale of the Quse Formation contains organic matters of types II1 and II2,with the average TOC of 8.34%,the average content of chloroform bitumen'A'of 0.66%,the average residual hydrocarbon generation potential(S1+S2)of 29.93 mg/g,and the Ro value of 0.9%–1.3%,meeting the standard of high-quality source rock.The organic-rich shale of the Bagong Formation contains mixed organic matters,with the TOC of 0.65%–3.10%and the Ro value of 1.17%–1.59%,meeting the standard of moderate source rock.Fourth,four shallow wells(depth of 50–250 m)with oil shows have been found in the organic shales at 50–90 m in the lower part of the Bagong Formation and 30–75 m in the middle part of the Quse Formation.The crude oil contains a high content of saturated hydrocarbon.Analysis and testing of outcrop and shallow well samples confirm the presence of marine shale oil in the Bagong Formation and the Quse Formation.Good shale oil intervals in the Bagong Formation are observed in layers 18–20 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 206.7 m thick,with the maximum and average(S0+S1)of 1.92 mg/g and 1.81 mg/g,respectively.Good shale oil intervals in the Quse Formation are found in layers 4–8 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 58.8 m thick,with the maximum and average(S0+S1)of 6.46 mg/g and 2.23 mg/g,respectively.展开更多
During Permian and Triassic the western margin of Upper Yangtze platform had experienced an evolution from early rift stage to thermal subsidence and then to foreland basin. The tectonic transformations have resulted...During Permian and Triassic the western margin of Upper Yangtze platform had experienced an evolution from early rift stage to thermal subsidence and then to foreland basin. The tectonic transformations have resulted in five supersequences and nineteen third-order se- quences.During the rift stage,transgeressive carbonate platform was built up,while in the thermal subsidence stage,regressive carbonate platform with foreslope was formed.The closure of the Garze-Litang narrow oceanic basin resulted in the migration of foreland flexure toward the ctaton.The carbonate ramp in foreland basin setting was formed during the relative sea level rise which was caused by the change in basin volume.展开更多
基金Projects(41506080,41702162)supported by the National Natural Science Foundation of ChinaProjects(DD20160152,DD20160147,GZH200800503)supported by China Geological Survey+1 种基金Projects(XQ-2005-01,2009GYXQ10)supported by China Ministry of Land and ResourcesProject(201602004)supported by the Postdoctoral Innovation Foundation of Shandong Province,China
文摘In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.
基金supported by the National Natural Science Foundation(Nos.41172099,41272130)
文摘Study of dolomite texture can contribute to understanding the process of dolomitization.This research reports textures and homogenization temperatures of dolomites from the Permian-Triassic strata in the Sichuan Basin and the Lower Paleozoic strata in the Tarim Basin,which provided insights into relationships between dolomite textures and their formation temperatures.Our results are summarized as follows：1） dolomites with well-preserved texture indicate low dolomitization temperature.However,in certain diagenetic environments,the hydrothermal dolomitization may completely or partially preserve the original texture of dolomites.2） The formation temperatures of non-planar dolomites are always higher than those of planar dolomites.3） The formation temperatures of dolomite cements are generally higher than those of replacive dolomites.4） Although the formation temperatures of saddle dolomite cements have a wide range,they show higher values than those of the planar subhedral to euhedral dolomite cements.Thus,saddle dolomites could generally be an indicator of high precipitation temperature.5） The fluid Mg/Ca ratio is another element controlling dolomite morphology.Micritic dolomites,which precipitate from hypersaline fluids with a high Mg/Ca ratio in a subaerial environment could also have features of non-planar anhedral crystal shape because of rapid nucleation and crystallization during dolomitization.
基金Supported by the PetroChina Science and Technology Major Project(2021DJ08)National Natural Science Foundation of China(42241203).
文摘Mesozoic marine shale oil was found in the Qiangtang Basin by a large number of hydrocarbon geological surveys and shallow drilling sampling.Based on systematic observation and experimental analysis of outcrop and core samples,the deposition and development conditions and characteristics of marine shale are revealed,the geochemical and reservoir characteristics of marine shale are evaluated,and the layers of marine shale oil in the Mesozoic are determined.The following geological understandings are obtained.First,there are two sets of marine organic-rich shales,the Lower Jurassic Quse Formation and the Upper Triassic Bagong Formation,in the Qiangtang Basin.They are mainly composed of laminated shale with massive mudstone.The laminated organic-rich shale of the Quse Formation is located in the lower part of the stratum,with a thickness of 50–75 m,and mainly distributed in southern Qiangtang Basin and the central-west of northern Qiangtang Basin.The laminated organic-rich shale of the Bagong Formation is located in the middle of the stratum,with a thickness of 250–350 m,and distributed in both northern and southern Qiangtang Basin.Second,the two sets of laminated organic-rich shales develop foliation,and various types of micropores and microfractures.The average content of brittle minerals is 70%,implying a high fracturability.The average porosity is 5.89%,indicating good reservoir physical properties to the level of moderate–good shale oil reservoirs.Third,the organic-rich shale of the Quse Formation contains organic matters of types II1 and II2,with the average TOC of 8.34%,the average content of chloroform bitumen'A'of 0.66%,the average residual hydrocarbon generation potential(S1+S2)of 29.93 mg/g,and the Ro value of 0.9%–1.3%,meeting the standard of high-quality source rock.The organic-rich shale of the Bagong Formation contains mixed organic matters,with the TOC of 0.65%–3.10%and the Ro value of 1.17%–1.59%,meeting the standard of moderate source rock.Fourth,four shallow wells(depth of 50–250 m)with oil shows have been found in the organic shales at 50–90 m in the lower part of the Bagong Formation and 30–75 m in the middle part of the Quse Formation.The crude oil contains a high content of saturated hydrocarbon.Analysis and testing of outcrop and shallow well samples confirm the presence of marine shale oil in the Bagong Formation and the Quse Formation.Good shale oil intervals in the Bagong Formation are observed in layers 18–20 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 206.7 m thick,with the maximum and average(S0+S1)of 1.92 mg/g and 1.81 mg/g,respectively.Good shale oil intervals in the Quse Formation are found in layers 4–8 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 58.8 m thick,with the maximum and average(S0+S1)of 6.46 mg/g and 2.23 mg/g,respectively.
文摘During Permian and Triassic the western margin of Upper Yangtze platform had experienced an evolution from early rift stage to thermal subsidence and then to foreland basin. The tectonic transformations have resulted in five supersequences and nineteen third-order se- quences.During the rift stage,transgeressive carbonate platform was built up,while in the thermal subsidence stage,regressive carbonate platform with foreslope was formed.The closure of the Garze-Litang narrow oceanic basin resulted in the migration of foreland flexure toward the ctaton.The carbonate ramp in foreland basin setting was formed during the relative sea level rise which was caused by the change in basin volume.
