中江气田河道砂岩优质储层特征及主控因素

Characteristics and Main Controlling Factors of High QualityChannel Sandstone Reservoir in Zhongjiang Gas Field

中江气田沙溪庙组河道砂岩储层物性普遍较差,优质储层是控制油气富集高产的主要因素之一。利用铸体薄片、扫描电镜、X衍射和岩芯物性分析资料对优质储层的特征及其主控因素进行分析。结果表明,优质储层孔隙类型以粒间溶孔和残余粒间孔为主,成岩相主要为绿泥石胶结相和绿泥石胶结溶蚀相。早期衬边状绿泥石胶结和晚期溶蚀作用是优质储层形成的关键,构造破裂作用导致的微裂缝能够提高储层渗流能力,对于优质储层的形成也具有促进作用。主分流河道水动力条件强、颗粒粒度大、泥质含量少且早期绿泥石薄膜更为发育,更有利于优质储层的形成;长石含量高的次分流河道次生溶孔发育,储层物性也较好,因此,优质储层多发育于主分流河道和部分长石含量较高的次分流河道微相。

The sandstone reservoirs of Shaximiao Formation in Zhongjiang Gas Field are generally poor in physical properties.High quality reservoirs are one of the main factors controlling oil and gas enrichment and high yield.The characteristics and controlling factors of high quality reservoir are studied by casting thin section,scanning electron microscope,X diffraction and core physical property analysis data.The results show that the pore types of high quality reservoirs are mainly intergranular dissolved pores and residual intergranular pores,and the diagenetic facies are mainly chlorite cemented facies and chlorite cemented dissolution facies.Early lining chlorite cementation and late dissolution are the key to the formation of high quality reservoirs.Microfractures caused by structural fracture can improve the seepage capacity of reservoirs and promote the formation of high quality reservoirs.The main distributary channel has strong hydrodynamic conditions,large particle size,less argillaceous content and more developed chlorite film in the early stage,which is more conducive to the formation of highquality reservoirs.The secondary dissolution pores are developed in the secondary distributary channels with high feldspar content,and the reservoirs have good physical properties.Therefore,the high quality reservoirs are mostly developed in the main distributary channels and some secondary distributary channel microfacies with high feldspar content.