四川盆地蜀南地区长兴组油气成藏时空匹配

Spatial-temporal modelling of oil and gas accumulation in Changxing Formation in the Shunan area, Sichuan Basin

李延钧 夏吉文 李明隆 蒲洪果 耿超 王浩

LI Yanjun XIA Jiwen LI Minglong PU Hongguo GENG Chao WANG Hao

油气藏地质及开发工程国家重点实验室, 西南石油大学, 成都 610500 成都创源油气技术开发有限公司, 成都 610500 中国石油 西南油气田分公司 蜀南气矿, 四川 泸州 646000 中国石化 河南油田分公司 勘探开发研究院, 河南 南阳 473132

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China Chengdu Chuangyuan Oil and Gas Technology Development Company, Chengdu, Sichuan 610500, China Shunan Gas Field, PetroChina Southwest Oil&Gas Field Company, Luzhou, Sichuan 646000, China Exploration&Development Research Institute of Henan Oilfield Company, SINOPEC, Nanyang, Henan 473132, China

四川盆地蜀南地区上二叠统长兴组下伏3套烃源岩，分别为下志留统龙马溪组泥页岩、中二叠统泥质岩、上二叠统龙潭组煤系，长兴组已发现多个大中型气田，但对天然气的烃源一直认识不清。通过天然气组成和碳同位素分析表明，该区长兴组天然气以原油裂解气为主、甲烷含量高、干燥系数大，属于典型的干气；结合储层显微特征和包裹体均一温度分析测试，并综合分析油气成藏时空匹配关系，首次发现并证实蜀南地区长兴组天然气主要来源于深层志留系烃源岩，并混入少量的龙潭组煤系成因气；长兴组储层未捕获各期烃源岩生油高峰期生成的液态烃，以充气聚气为主；燕山运动早中期为主要充气期，而燕山末期—喜马拉雅早期为局部天然气充气期，与川东地区长兴组以龙潭组煤系来源的天然气不同。油气成藏时空匹配是圈闭有效捕获油气的关键，决定着油气来源和成藏富集程度，历史地、动态地揭示油气运聚过程是现代油气成藏研究的核心。

There are three sets of source rocks below the Changxing Formation in the southern Sichuan Basin, including the mud shale in Lower Silurian Longmaxi Formation, the argillaceous rock in Middle Permian, and the coal series in Upper Permian Longtan Formation. Many large and medium-sized gas fields have been discovered in the Changxing Formation, but the understanding of the source of natural gas is still unclear. The natural gas composition and carbon isotope analyses show that the natural gas of Changxing Formation in this area is mainly secondary gas (from crude oil cracking) and is characterized by high methane content and high dryness coefficient, which belongs to typical dry gas. Combined with the reservoir microscopic characteristics and the inclusion homogenization temperatures, a spatial-temporal model of hydrocarbon accumulation was constructed. The natural gas of Changxing Formation in the southern Sichuan Basin is mainly from a deep Silurian hydrocarbon source mixed with a small amount of coal series gas in the Longtan Formation. The reservoir in Changxing Formation did not capture the liquid hydrocarbon generated by the source rock at the peak of oil generation stages, so it mainly accumulates gas. The early and middle period of Yanshan Movement is the main period of gas accumulation, with partial accumulation in the Yanshanian-early Himalayan. The natural gas of Changxing Formation in the southern Sichuan Basin is different from that in the eastern Sichuan which is mainly from the coal series. The spatial-temporal timing is the key to effectively capture oil and gas in traps and determines the source and accumulation enrichment of oil and gas. It is the core of modern petroleum accumulation research to reveal the migration and accumulation process of oil and gas through history.

国家杰出青年科学基金 51125019;国家科技重大专项 2016ZX05004002-001

https://doi.org/10.11781/sysydz202006877