平落坝气田中、上侏罗统致密碎屑岩储集层特征

Characteristics of tight clastic reservoir of Middle and Upper Jurassic in Pingluoba Gas Field, West Sichuan Basin

川西地区平落坝气田中、上侏罗统包括沙溪庙组、遂宁组和蓬莱镇组,是广泛分布于川西地区典型的"红层"沉积,属非常规的致密碎屑岩储层,以孔隙度低、渗透性差为主要特征。储层相对发育的重要控制因素包括原始沉积环境和成岩作用,其中有利沉积相控条件下的砂体,配合建设性成岩作用的改善,储层往往比较发育。沙溪庙组砂岩以粒间溶蚀孔隙和粒内溶蚀孔隙为主,而上覆遂宁组和蓬莱镇组则以残余原生粒间孔和粒内溶蚀孔隙为主,但裂缝都比较发育,为储层提供重要的储集空间和渗滤通道,产气层对裂缝发育程度的依赖性比较大。中、上侏罗统以发育高角度缝为主,对储集层改善作用明显,预测并落实裂缝发育区是提高天然气产量的关键。

There are Shaximiao Formation, Suining Formation and Penglaizhen Formation in Middle and Upper Jurassic reservoir of West Sichuan Basin. It widely develops the typical ＂Red Beds＂ sediments, which is unconventional＂ tight clastic reservoir with low porosity and permeability. The original depositional environment and diagenesis are important controlling factors for reservoir. And it usually develops the sand body controlled by the favorite sedimentary facies and improved by constructional diagenesis. Intergranular dissolution and intragranular dissolution pores are key pore spaces in Shaximiao Formation. However, the residual primary intergranular and intragranular dissolution pores are mainly pore types in overlying Suining Formation and Penglaizhen formation. The fractures develop well, which are important reservoir pore spaces and filtration channel of reservoir. The fractures are mainly high angle fractures which can improve reservoir obviously. Therefore, the key of increasing gas production in this area is to predict and define the fracture growing area.