西湖凹陷深层有效储层形成机理及深度下限研究

Study on Genetic Mechanism and Lower Limit of Deep Effective Reservoirs in the Xihu Sag

为了明确西湖凹陷有效储层形成机理,实施海上经济有效勘探开发战略,文章综合运用铸体薄片、扫描电镜、恒速压汞、X衍射和DST测试等技术方法,从源—汇—岩三方面分析了西湖凹陷有效储层的成因、发育规律,并探讨了其发育的深度下限。结果表明,有效储层的形成受控于物源、沉积和成岩的共同作用,西湖凹陷周边以岩浆岩(特别是花岗岩)、变质岩为主的母岩来源,大型辫状河、三角洲—潮坪的强水动力沉积背景,为西湖凹陷深层低渗背景下有效储层的发育提供了有利的先天条件,后期成岩作用对储层孔喉结构的改造决定了有效储层纵向分布。有利沉积微相、溶蚀强度大和早期绿泥石发育是控制西湖凹陷有效储层发育的主控因素,低地温、超压发育背景下的洁净的中、粗和含砾中粗砂岩储层决定了有效储层发育的下限。

In order to clarify the formation mechanism of effective reservoir in the Xihu sag and implement the strategy for the development of marine economy effective exploration,we used thin section identification,scanning electron microscopy,constant rate mercury injection,X-ray diffraction and DST tests to analyze the genesis and development of effective reservoirs in the Xihu sag from three aspects including source,sink,and lithology,and discusses the lower limit of their development depth.The result shows that the formation of effective reservoir is controlled by provenance,sedimentation,and diagenesis.The igneous(especially granite)and metamorphic rocks occur around the Xihu Sag.The strong hydrodynamics of large braided river-delta-tidal flat sedimentary environment provides conditions for the development of effective reservoirs under deep low permeability in the Xihu Sag,while transformation of pore throat structures by diagenesis determines vertical distribution of effective reservoirs.Favorable sedimentary microfacies,strong dissolution and early chlorite development are the main factors controlling effective reservoir development in the Xihu Sag.Clean medium-coarse and gravel-bearing medium-coarse sandstone reservoirs under low geothermal and overpressured development determine the lower limit of effective reservoir development.