鄂尔多斯盆地北部新召地区山西组砂岩储层压力演化与低压成因OA
Pressure evolution and underpressure generation in the Shanxi Formation sandstone reservoirs of the Xinzhao area,northern Ordos Basin
鄂尔多斯盆地北部新召地区上古生界砂岩储层富含天然气且普遍发育异常低压,对古压力演化以及现今异常低压形成机理认识尚不够深入,制约了致密砂岩气成藏规律的认识和增储上产.运用流体包裹体岩相学观察、显微测温和激光拉曼分析技术,综合分析山西组二段储层中油气充注历史,获取成藏关键时期的古压力;利用盆地模拟法恢复古压力演化史,建立古流体压力演化与油气充注的耦合关系,并进一步探讨异常低压成因与致密气成藏的成因联系.研究表明:(1)研究区山二段CO2 包裹体捕获于距今 180～170 Ma,此时烃源岩处于中-低成熟阶段,甲烷包裹体捕获于距今 138～121 Ma的生烃高峰期;(2)山二段储层在早侏罗世开始发育超压,并在早白垩世末规模达到最大,古压力及古压力系数约为 50 MPa和 1.31;(3)由于温度降低、孔隙反弹和气体扩散等因素造成山二段地层压力降低分别约占总地层压力下降幅度的 49%,14.5%和 36.5%.山二段储层经历了常压-中等超压-常压-低压的演变过程,生烃增压与压力传导是古超压形成的主要原因,温度降低和天然气扩散是山二段异常低压形成的主控因素.
[Objective]The Upper Paleozoic sandstone reservoirs in the Xinzhao area,northern Ordos Basin,are rich in natural gas and characterized by underpressure.The mechanisms of paleo-pressure evolution and underpressure generation are unclear,constraining the understanding of tight sandstone gas accumulation and the enhancement of natural gas production.[Methods]This study comprehensively analyzed the petroleum charging history in the second member of the Shanxi Formation using fluid inclusion petrographic,micrometry,and laser Raman analysis.Subsequently,we obtained the paleo-pressure during the key reservoir formation period.The paleo-pressure evolution history was established by the basin simulation methods,and the coupling between paleo-fluid pressure evolution and petroleum charging was established.The relationship between the causes of underpressure and tight gas accumulation is further discussed.[Results]The results indicate that:①CO2 was trapped in the second member of the Shanxi Formation in the Xinzhao area from 180 to 170 Ma,when the source rock was at a middle-low maturity stage,and the methane inclusion was captured at the peak of hydrocarbon generation from 138 to 121 Ma.②Overpressure in the second member of the Shanxi Formation began developing in the Early Jurassic and reached a maximum paleo-pressure of 50 MPa and a paleo-pressure coefficient of 1.31 by the end of the Early Cretaceous.③The formation pressure decrease in the second member of the Shanxi Formation,driven by temperature drop,pore rebound,and gas diffusion,accounted for 49%,14.5%,and 36.5%of the total formation pressure decrease,respectively.[Conclusion]The tight gas reservoir in the second member of the Shanxi Formation experienced a pressure evolution from normal pressure to medium overpressure,back to normal pressure,and finally to underpressure.Hydrocarbon-generation-induced overpressure and pressure-conduction are the main factors contributing to ancient overpressure,while temperature decrease and natural-gas diffusion are the primary factors driving underpressure formation in the second member of the Shanxi Formation.
景海杰;王琳霖;任克雄;叶云飞;刘宇坤;陈芳;马立元;侯宇光
中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉 430074中国石化石油勘探开发研究院,北京 100083宜昌市夷陵区自然资源和规划局,湖北 宜昌 443100中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉 430074中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉 430074中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉 430074中国石化石油勘探开发研究院,北京 100083中国地质大学(武汉)构造与油气资源教育部重点实验室,武汉 430074
天文与地球科学
致密砂岩储层古压力演化低压成因山二段鄂尔多斯盆地
tight sandstone reservoirpaleo-pressure evolutionunderpressure generationsecond member of the Shanxi FormationOrdos Basin
《地质科技通报》 2026 (1)
81-94,14
中国石化科技部项目(P21088-2)国家自然科学基金(41772143)
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