断陷湖盆致密砂砾岩储层特征及主控因素

为了明确徐家围子断陷沙河子组致密砂砾岩储层发育特征和控制因素,通过岩心观察、薄片分析、电镜扫描、压汞分析和岩石物性测试等手段,对储层的岩石学、储集空间、沉积作用、成岩作用等与物性关系进行了分析。结果表明:砂砾岩储层富含长石、火山岩屑、填隙物等低成熟组分,分选差,岩石颗粒多常见线—凹凸接触;储集空间类型主要为长石溶孔、岩屑溶孔,其次为残余粒间孔、晶间孔、微裂缝;致密砂砾岩孔隙度多数小于6%,渗透率一般小于0.1×10~(-3)μm~2,平均孔喉半径0.01～0.14μm,排驱压力高,孔喉连通性差;储层特征受沉积和成岩作用共同控制,砂砾岩孔隙度与刚性、塑性组分含量密切相关,扇三角洲和辫状河三角洲河道砂体物性较好,强烈压实作用平均减少孔隙度15%～20%,有机酸溶蚀作用平均增加孔隙度4.7%,晚期胶结通过充填残余粒间孔和溶蚀孔平均减少孔隙度4.2%。

CHARACTERISTICS AND THEIR CONTROLLING FACTORS FOR THE TIGHT CONGLOMERATE RESERVOIR IN THE FAULT DEPRESSION LAKE BASIN

In order to make clear of the developed characteristics and their dominant controlling factors of the tight conglomerate/glutenite reservoirs in Shahezi Formation of Xujiaweizi Fault Depression,with the help of the core observation,thin section analysis,scanning electron microscope,mercury penetration analysis,petrophysical property test and so on,the following relationships were analyzed between the physical properties and the reservoir petrology,AS (accumulation space),sedimentation,diagenesis and so forth.The achievements show that the conglomerate reservoirs are enriched with the low-maturity components including the feldspar,volcanic debris,interstitial matter and so on,the sorting is rather poor,the line-concave/convex connectivities are commonly seen among the rock particles;the main AS types are the feldspar and debris dissolved pores,the next is the residual intergranular and intercrystalline pores and mircofractures;most of the porosity of the tight conglomerate are less than 6％,the permeabilities are generally less than 0.1 × 10-3 μm2,the average pore radii are 0.01-0.14 μm,the expulsion pressure is rather higher,the connectivity among the pores is rather poorer;the reservoir characteristics are both controlled by the sedimentation and diagenesis,the conglomerate porosity is closely related with the contents of the rigid and plastic components,the physical properties of the sandbodies of the fan and braided delta channels are pretty better,the porosity is averagely reduced by 15％-20％ by the strong compaction,on the contrary,the porosity is averagely increased by 4.7％ by the organic acid dissolution,the porosity is averagely reduced by 4.2％ by filling the residual intergranular and dissolved pores at the late stage of the cementation.