四川盆地雷口坡组膏盐岩成因及其油气地质意义

Genesis of gypsum-salt in the Leikoupo Formation and its hydrocarbon significance in the Sichuan Basin,China

探讨四川盆地中三叠统雷口坡组膏盐岩的形成与分布及其对成烃和成储的影响。在岩心、薄片、测井和钻井等资料分析的基础上,对雷口坡组膏盐岩的岩石学特征、岩性组合特征和测井特征等开展研究发现,雷口坡组膏盐岩层系发育云岩+膏盐岩、膏岩+云岩、灰岩+膏盐岩、膏盐岩+灰岩4种组合类型,以及潮上塞卜哈、潮上小型蒸发盐盆、潟湖和蒸发盐盆4种成因模式。雷一段-雷二段面状展布的膏盐岩以塞卜哈成因为主,龙岗地区雷一段发育环带状展布的小型蒸发盐盆;雷三段发育以川中为中心、呈水滴式展布的潟湖成因膏盐岩;雷四段在川西南-川西地区发育牛眼式展布的蒸发盐盆成因膏盐岩。川西地区雷四段膏盐岩层系中发育有品质较好的烃源岩和以膏溶孔、洞为主要储集空间的岩溶储层,具备优越的油气地质条件,是下一步勘探的有利目标。

The formation and distribution of gypsum-salt in Upper Triassic Leikoupo Formation possess an important influence on hydrocarbon generation and reservoir development in the west Sichuan Basin. The gypsum-salt in Upper Triassic Leikoupo Formation has 4 types of lithological assemblages,the dolomite +gypsum-salt,the gypsum-salt + dolomite,the limestone + gypsum-salt and the gypsum-salt + limestone,which correspond to 4 types of genetic models of sabkha,salt lake in the supratidal environment,lagoon and evaporate basin. Gypsum-salt deposited in sabkha environment distributes widely during the Member 1 and Member 2 of Leikoupo Formation in most part of Sichuan Basin, except the Longgang area which developed in salt lake of supratidal environment. Gypsum-salt in the Member 3 of Leikoupo Formation deposited in lagoon environment in central Sichuan Basin. The gypsum-salt of Member 4 of Leikoupo Formation deposited in evaporate basin environment and it is the favorable reservoir with well developedgypsum dissolution pores,and therefore,is the favorable target for the future exploration of gas and oil in west Sichuan Basin.