Cambrian shales in China and elsewhere contain abundant oil and gas resources.However,due to its deep burial and limited outcrop,there has been relatively little research conducted on it.The Cambrian shale of the Tado...Cambrian shales in China and elsewhere contain abundant oil and gas resources.However,due to its deep burial and limited outcrop,there has been relatively little research conducted on it.The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China,specifically the Xidashan-Xishanbulake Formation(Fm.)and overlying Moheershan Fm.provide a case study through the use of organic petrology,mineralogy,organic and elemental geochemistry,with the aim of analyzing and exploring the hydrocarbon generation potential(PG)and organic matter(OM)enrichment mechanisms within these shale formations.The results indicate that:(1)the Cambrian shale of the Tadong low uplift exhibits relatively dispersed OM that consists of vitrinite-like macerals and solid bitumen.These formations have a higher content of quartz and are primarily composed of silica-based lithology;(2)shale samples from the Xidashan-Xishanbulake and Moheershan formations demonstrate high total organic carbon(TOC)and low pyrolytic hydrocarbon content(S_(2))content.The OM is predominantly typeⅠand typeⅡkerogens,indicating a high level of maturation in the wet gas period.These shales have undergone extensive hydrocarbon generation,showing characteristics of relatively poor PG;(3)the sedimentary environments of the Xidashan-Xishanbulake and Moheershan formations in the Tadong low uplift are similar.They were deposited in warm and humid climatic conditions,in oxygen-deficient environments,with stable terrigenous inputs,high paleoproductivity,high paleosalinity,weak water-holding capacity,and no significant hydrothermal activity;and(4)the relationship between TOC and the paleoproductivity parameter(P/Ti)is most significant in the Lower Cambrian Xidashan-Xishanbulake Fm.,whereas correlation with other indicators is not evident.This suggests a productivity-driven OM enrichment model,where input of landderived material was relatively small during the Middle Cambrian,and the ancient water exhibited lower salinity.A comprehensive pattern was formed under the combined control of paleoproductivity and preservation conditions.This study provides valuable guidance for oil and gas exploration in the Tarim Basin.展开更多
Focusing on the two natural gas exploration geological problems with abundant source of oil cracking gas in the late stage and the sealing condition of the oil cracking gas reservoir,the kinetics of oil cracking gas a...Focusing on the two natural gas exploration geological problems with abundant source of oil cracking gas in the late stage and the sealing condition of the oil cracking gas reservoir,the kinetics of oil cracking gas and the evaluation parameters of gas cap rock are adopted to the study on the natural gas accumulation conditions in the Tadong area.Both the study on the kinetics of oil cracking gas and the statistical results of reservoir bitumen reveal that the geological formation of oil cracking gas in the Tadong area is located in the top of Cambrian.Two kinds of oil cracking gas geological models at least,namely well Mandong-1's early rapid generation model(Middle Ordovician-end Silurian)and peak cracking model(with the natural gas conversion rate>90%),namely well Yingnan-2's two-stage generation model of oil cracking gas,have been set up.The oil cracking gas of Yingnan-2 in the late stage is very significant in the evaluation of natural gas exploration in the Tadong area.The evaluation results of the cap rock show that the microscopic parameters of cap rock from the lower assemblage of Cambrian-Ordovician are better than those from the upper assemblage.The former has strong capillary sealing ability and higher cap rock breakthrough pressure than the upper assemblage,with strong sealing ability,so that natural gas dissipates mainly by diffusion.According to the above investigations,the lower assemblage Cambrian-Ordovician natural gas of Kongquehe slope,Tadong low uplift and Yingjisu depression in the Tadong area prospects well.展开更多
基金supported by the National Major Science and Technology Project of China(Grant Nos.2016ZX05066001-0022017ZX05064-003-001+3 种基金2017ZX05035-02 and 2016ZX05034-001-05)the Innovative Research Group Project of the National Natural Science Foundation of China(Grant Nos.4187213542072151 and 42372144)the Project of Education Department of Liaoning Province(Grant No.LJKMZ20220744)。
文摘Cambrian shales in China and elsewhere contain abundant oil and gas resources.However,due to its deep burial and limited outcrop,there has been relatively little research conducted on it.The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China,specifically the Xidashan-Xishanbulake Formation(Fm.)and overlying Moheershan Fm.provide a case study through the use of organic petrology,mineralogy,organic and elemental geochemistry,with the aim of analyzing and exploring the hydrocarbon generation potential(PG)and organic matter(OM)enrichment mechanisms within these shale formations.The results indicate that:(1)the Cambrian shale of the Tadong low uplift exhibits relatively dispersed OM that consists of vitrinite-like macerals and solid bitumen.These formations have a higher content of quartz and are primarily composed of silica-based lithology;(2)shale samples from the Xidashan-Xishanbulake and Moheershan formations demonstrate high total organic carbon(TOC)and low pyrolytic hydrocarbon content(S_(2))content.The OM is predominantly typeⅠand typeⅡkerogens,indicating a high level of maturation in the wet gas period.These shales have undergone extensive hydrocarbon generation,showing characteristics of relatively poor PG;(3)the sedimentary environments of the Xidashan-Xishanbulake and Moheershan formations in the Tadong low uplift are similar.They were deposited in warm and humid climatic conditions,in oxygen-deficient environments,with stable terrigenous inputs,high paleoproductivity,high paleosalinity,weak water-holding capacity,and no significant hydrothermal activity;and(4)the relationship between TOC and the paleoproductivity parameter(P/Ti)is most significant in the Lower Cambrian Xidashan-Xishanbulake Fm.,whereas correlation with other indicators is not evident.This suggests a productivity-driven OM enrichment model,where input of landderived material was relatively small during the Middle Cambrian,and the ancient water exhibited lower salinity.A comprehensive pattern was formed under the combined control of paleoproductivity and preservation conditions.This study provides valuable guidance for oil and gas exploration in the Tarim Basin.
基金Supported by PetroChina Foundation Project(Grant No.07-01C-01-07)Na-tional Basic Research Program of China(Grant No.2007CB209503)
文摘Focusing on the two natural gas exploration geological problems with abundant source of oil cracking gas in the late stage and the sealing condition of the oil cracking gas reservoir,the kinetics of oil cracking gas and the evaluation parameters of gas cap rock are adopted to the study on the natural gas accumulation conditions in the Tadong area.Both the study on the kinetics of oil cracking gas and the statistical results of reservoir bitumen reveal that the geological formation of oil cracking gas in the Tadong area is located in the top of Cambrian.Two kinds of oil cracking gas geological models at least,namely well Mandong-1's early rapid generation model(Middle Ordovician-end Silurian)and peak cracking model(with the natural gas conversion rate>90%),namely well Yingnan-2's two-stage generation model of oil cracking gas,have been set up.The oil cracking gas of Yingnan-2 in the late stage is very significant in the evaluation of natural gas exploration in the Tadong area.The evaluation results of the cap rock show that the microscopic parameters of cap rock from the lower assemblage of Cambrian-Ordovician are better than those from the upper assemblage.The former has strong capillary sealing ability and higher cap rock breakthrough pressure than the upper assemblage,with strong sealing ability,so that natural gas dissipates mainly by diffusion.According to the above investigations,the lower assemblage Cambrian-Ordovician natural gas of Kongquehe slope,Tadong low uplift and Yingjisu depression in the Tadong area prospects well.
