陵水凹陷北坡海底扇孔隙演化和成岩相研究

琼东南盆地陵水凹陷北坡海底扇储层岩性较细,物性较差,并且对其低渗的成因不明、甜点的展布也不清。通过利用岩石薄片、扫描电镜、粒度分析、压汞以及物性等资料来分析其孔隙演化,并从成岩相的研究角度来预测其甜点展布。研究结果认为研究区梅山组二段储层孔隙类型主要为原生粒间孔和铸模孔,处在中成岩阶段A期。从沉积因素和成岩作用两个方面总结出了研究区的孔隙演化模式:沉积环境控制了原始孔隙度的大小,后期机械压实是孔隙减小的主要原因,溶解作用对孔隙增大起到了巨大贡献。研究区主要识别和划分出了中等压实长石溶蚀相、中等压实海绿石胶结相和强压实弱溶蚀相3种成岩相,甜点主要分布在水动力较强的海底扇内扇中等压实长石溶蚀相中。

Porosity Evolution and Diagenetic Facies Study of Submarine Fan Reservoir in North Slope of Lingshui Sag

The submarine fan reservoir in the north slope of Lingshui sag, Qiongdongnan basin are characterized by fine grain, unclear genesis of low permeability and unknown distribution of the "sweet spot". This paper analyzed the porosity evolution and diagenetic facies based on the rock thin section, scanning electron microscopy, mercury injection experiment, particle size and petrophysics data. Besides, the "sweet spot" was predicted from the aspect of diagenetic facies. The results showed that primary porosity and mould pore are the main pore type in the 2nd member of Meishan Formation reservoir. The target intervals was in the middle diagenesis A stage. Porosity evolution was discussed according to sedimentation factors and diagenesis as follows:Primary pore were controlled by depositional environment, which were decreased sharply by later mechanical compaction; Dissolution played a great role in porosity increasing. Middle compaction-feldspar dissolution, middle compaction-glauconite cementation, strong compaction-weak dissolution were identified in the study area. The "sweet spot" was distributed in the inner submarine fan which had strong hydrodynamic condition and developed middle compaction-feldspar dissolution.