川西南龙门硐地区雷口坡组成岩作用及其对储层的影响

Diagenesis and Its Effects on the Reservoir of Leikoupo Formation in Longmendong Area of Southwestern Sichuan

雷口坡组地层是四川盆地主要的含油气层系之一,目前对雷口坡组地层的研究主要集中在川东北、川中地区。为了明确川西南峨眉龙门硐地区雷口坡组地层的储层特征和成岩作用类型,通过实地踏勘考察和光学显微镜岩石薄片鉴定,对龙门硐地区雷口坡组地层的优质储层发育段和成岩作用对储层发育的影响进行研究。结果表明:雷一段以泥晶碳酸盐岩为主,储集性能差;雷二段的颗粒滩相碳酸盐岩、雷三段的灰质泻湖相灰岩和颗粒滩相碳酸盐岩,雷四段的岩溶角砾岩为优质储集层;不同的有利储集层段所经历的主要成岩作用不同。研究认为:雷口坡组二段、三段的有利储集层段所经历的主要建设性成岩作用为埋藏期溶蚀作用、渗透回流白云石化和埋藏期白云石化作用,白云石化作用为后期溶蚀作用的发生提供了有利条件;主要破坏性成岩作用为埋藏期胶结作用。雷口坡组四段的主要建设性成岩作用为表生期溶蚀作用。

The Leikoupo Formation is one of the main hydrocarbon-bearing strata in the Sichuan Basin.At present,the research on the Leikoupo Formation is mainly concentrated in the Northeastern Sichuan and central Sichuan.In order to clarify the reservoir characteristics and diagenesis types of the Leikoupo Formation in the Longmendong area of Southwestern Sichuan,field investigation trips and rock slices identification by light microscope were used to study the diagenesis and its effects on the reservoir of leikoupo formation in the study area.The results show that the first member of the Leikoupo Formation mainly contains micrite carbonate rocks and the reservoirs properties is bad;the sand shoals carbonate rocks of the second member of the Leikoupo Formation、the limestone developing in lagoon and the sand shoals carbonate rocks of the third member of the Leikoupo Formation、the karst breccia of the fourth member are high-quality reservoirs.The different good reservoir sections are in control of different diagenesis.It is concluded that the main constructive diagenesis experienced by the favorable reservoirs in the second and third members of the Leikoupo Formation are burial dissolution、reflux dolomitization and the burial dolomitization,and this two dolomitizations provide advantages for the occurrence of later dissolution,and the main destructive diagenesis is burial cementation.The main constructive diagenesis of the fourth member of the Leikoupo Formation is the dissolution during the surface stage.