川西海相雷口坡组成藏地质特征及控制因素

Geological features and control factors of reservoir forming in middle Triassic Leikoupo Formation in western Sichuan Basin

对烃源岩、储集层、盖层、生烃史研究以及气源分析表明,川西地区发育下二叠统、上二叠统及中三叠统雷口坡组3套主力烃源岩,雷三段针孔状白云岩是雷口坡组最有利的储集层段,中三叠统顶部发育的膏盐层及上覆上三叠统和侏罗系厚层泥岩可以作为盖层,川西地区二叠系和中三叠统雷口坡组烃源岩分别在晚三叠世中晚期和三叠纪末—侏罗纪早期进入生烃高峰期.研究认为,川西地区雷口坡组成藏主控因素为:①古地理、微地貌控制有利储集层的分布;②粗结构滩体的暴露淋滤是形成良好储集性能的关键;③断裂、古构造控制油气的运移与聚集.对成藏地质特征及控制因素的研究认为研究区首选勘探目标是孝泉构造-岩性复合型圈闭,其次是回龙寺、鸭子河、白鹿场、大邑等构造-岩性复合型圈闭.

The study of hydrocarbon source rock,reservoir,caprock and hydrocarbon-generating history and the analysis of gas source shows that,three sets of main hydrocarbon source rock are developed in lower Permian series,upper Permian series and middle Triassic Leikoupo formation in the studied area,the pinhole dolomite in the third member of Leikoupo Formation is the most favorable reservoir,and the plaster rock at the top of middle Triassic series and the thick shale in upper Triassic and Jurassic are good caprock. The hydrocarbon generation peak periods of the hydrocarbon source rocks in Permian and middle Triassic Leikoupo formation are separately in the middle-late period of late Triassic and from the end of Triassic to early Jurassic. There are three main factors of controlling reservoir forming in middle Triassic Leikoupo Formation: paleogeography and microtopography controls the distribution of favorable reservoirs; the exposure and leaching of coarse beach body is key to form good reservoir property; faults and palaeostructures control the migration and accumulation of hydrocarbon. According to the study on the geological features and the control factors of reservoir forming, it is held that the first exploration target is the structural-lithological trap in Xiaoquan,and the secondary exploration targets are the structural-lithological traps in Huilongsi,Yazihe,Bailuchang and Dayi.