川西地区中三叠统雷口坡组储层特征及其形成条件

Characteristics and formation conditions of carbonate reservoir in Leikoupo Formation of western Sichuan Basin

近年来,四川盆地川西地区雷口坡组的油气勘探取得了丰富的成果,但是对雷口坡组碳酸盐岩储层特征及其控制因素的综合研究还相对薄弱,严重制约了雷口坡组进一步的油气勘探步伐。基于野外露头、岩心、测井等资料,结合实验分析数据,系统总结了川西地区雷口坡组储层的发育特征及其形成条件。研究表明:(1)川西地区雷口坡组储集岩主要以藻白云岩、颗粒白云岩和细粉晶云岩为主,粒间孔、晶间孔和生物格架孔是主要的孔隙空间,储层整体表现为低孔低渗特征;(2)沉积相和岩溶作用共同控制着川西地区雷口坡组储层的发育,其中沉积相是储层发育的物质基础,准同生期的白云石化和岩溶作用是孔隙规模保持和次生孔隙形成的主控因素,而中三叠世末期的表生岩溶作用起到加强和巩固的作用,埋藏期有机酸的溶蚀作用起到保护作用。

In recent years,there are many oil and gas discoveries in Triassic Leikoupo Formation in western Sichuan Basin, but the comprehensive studies on the characteristics of carbonate reservoir and the controlling factors are weak,which has seriously restricted the oil and gas exploration and development.Based on field outcrop, core observations, rock sections, logging data and the experiment data, systematic summarizationof the characteristics and formation conditions of carbonate reservoir in Leikoupo Formation in western Sichuan Basin,it is concluded that： （1）the main types of reservoir rock in Leikoupo Formation are algal dolomite, grainstone dolomite and crystal dolostones, and the main pore space are intergranular pore, intercrystal pore and biological framework pore.The characteristics of reservoir are low porosity and low permeability. （2）The reservoir developments in Leikoupo Formation in western Sichuan Basin are con- trolled by sedimentary microfacies and karstification. The sedimentary microfacies provide the material foundation for the development of the reservoir.The dolomitization and karst effect in Penecontemporaneous period are the key factors to form and maintain pore space.The late hypergenensis at the end of middle Triassic can strengthen and consolidate the pore space.The dissolution of organic acid and the residual oil and gas play an active protective role.