断陷盆地天然气运聚成藏史研究--以东濮凹陷文23气田为例

Research on history of gas migration and accumulation in fault basin: Taking Wen 23 Gas Field of Dongpu Depression as an example

天然气运聚成藏史包括天然气的来源、运移通道、充注过程、充注期次及成藏各要素的配置关系。以渤海湾盆地东濮凹陷文23气田为例,在油气地质综合研究基础上,借助天然气分析测试资料,对该气田沙四段气藏天然气生成、运移、聚集、保存等动态成藏过程进行了研究。结果表明,文23地区天然气主要来源于前梨园洼陷石炭-二叠系煤系源岩。在沙一段沉积期至东营组沉积末期,洼陷带生成的煤成气沿文东断层向上运移进入沙四段砂体,并沿着砂体高孔隙高渗透带向西北方向运聚,在沙四段储集层的有利部位聚集成藏,为一期连续充注成藏。其古气水界面比现今气藏的气水界面约低10m,表明文23沙四段气藏中的天然气在东营运动晚期存在一定程度的散失。

The history of gas migration and accumulation includes the origin, migration pathways, charging process, charging history of natural gas and the matching relations of the main factors for hydrocarbon accumulation. Taking Wen23 Gas Field in Dongpu Depression as a case, the dynamic processes of hydrocarbon generation, migration, accumulation and preservation of natural gas were discussed based on the comprehensive research of petroleum geology and test data. The natural gas in this area is mainly from the coal source rocks of the Permo Carboniferous system in Qianliyuan sub depression. The coal-formed gas migrated along the Wendong fault firstly to the sandstone in the fourth member of Shahejie Formation and then along the high-porosity and high-permeability zone of sand body towards the northwest. The coal formed gas continuously accumulated in the favorable place of the fourth member of Shahejie Formation reservoir in the period from the first member of Shahejie Formation depositional stage to the late of Dongying Formation. The original gas-water interface is about 10 m lower than that of gas reservoirs at present, which indicates that natural gas in the fourth member of Shahejie Formation reservoir of Wen23 Gas Field dissipated in the last stage of the Dongying movement to some extent.