潜江凹陷王场背斜潜四下段盐韵律层页岩储层孔隙结构特征

为了解潜江凹陷王场背斜潜四下段14号韵律层页岩储层孔隙结构特征及探讨岩石物性优越性的受控因素，开展了X射线粉晶全岩、岩石物性、高压压汞、氮气吸附、微米CT扫描及聚集离子束扫描等分析.研究显示:储层主要由白云石（平均40.5%）、方解石（平均10.4%）；长石（平均16.5%）、黏土矿物（平均11.2%）、硬石膏（平均10.8%）及石英（5.9%）构成；岩石为"高-中孔（平均17.6%），特低渗（平均0.043 6 mD）"储层类型；各岩性（除泥质灰岩）中大孔率高（平均79.7%）的特点促成了孔隙性的优良，白云石及方解石含量与大介孔率的相关性指示白云石化与大孔形成密切相关；白云石化协同方解石沉积带来的细小孔喉奠定了渗透性差的基础，硬石膏含量与几何迂曲度的正相关性指示硬石膏化对孔喉空间复杂度的加强及对渗透性的恶化，配位数少（主峰3个）及退汞效率低（平均40%）反映的连通性较差对渗透性亦有一定的影响. 

Pore Structure Characteristics of Shale Reservoir of the Lower Qian 4 Member in the Wangchang Anticline of the Qianjiang Sag

The analyses of X-ray powder diffraction,porosity and permeability,high pressure mercury,nitrogen adsorption,Micro-CT scanning,and FIB-SEM were performed,aiming to understand the pore structure characteristics of the shale reservoir and discuss the controlling factors of the superiority of rock physical property of of different lithologies of the 14th cyclotherm of the Lower Qian4 Member in the Wangchang anticline of the Qianjiang sag. Studies show that the reservoir consists mainly of dolomite (40.5% on average),calcite (10.4% on average),feldspar (16.5% on average),clay minerals (11.2% on average),anhydrite (10.8% on average),and quartz (5.9% on average); the rock is "high-medium porosity (average 17.6%) and very low permeability (average 0.043 6 mD)" type; high macropore rate (79.7% on average) within each lithology (except argillaceous limestone) contributes to excellent porosity,and the correlation between dolomite and calcite content and macopore and micropore rate indicates that dolomitization is closely related to the formation of macropore. Dolomiticzation along with calcite precipiatation lays the foundation of poor permeability,and the positive correlation between anhydrite content and geometrical tortuosity indicates the enhancement of the space complexity of the pore throat and the deterioration of permeability. The less connecting number (main peak at 3) and the low efficiency of mercury withdrawal (40% on average) reflect poor connectivity which also has a certain effect on permeability.