黑家堡地区长4+5_(2)致密砂岩孔隙结构特征及影响因素分析

Pore structure characteristics and influencing factors of Chang 4+5_(2) tight sandstone reservoir in Heijiapu area,Ordos Basin

针对鄂尔多斯盆地黑家堡地区长4+5_(2)致密储层孔隙结构复杂及影响因素不明的问题,利用测井、常规物性、扫描电镜、铸体薄片及高压压汞测试等方法,得到长4+5_(2)发育的四类孔隙结构,其中Ⅰ类和Ⅱ类为勘探目标首选,并将成果应用于长4+5油藏。实践结果表明,研究区长4+5_(2)储层平均孔隙度为10.43%,平均渗透率为0.79×10^(-3)μm ^(2),属于典型的致密砂岩储层,残余粒间孔为主要的储集空间类型;孔喉尺度主要以纳米级为主,其次为微米级,平均孔喉半径分布在0.02~10.00μm;Ⅰ类和Ⅱ类孔隙结构发育的水下分流河道和河口坝微相孔隙结构最优,为勘探和开发的重点目标。根据储层孔隙结构评价结果,在研究区划分出三类勘探区带,作为勘探开发的优选区。细粒砂岩沉积为长4+5_(2)不同孔隙结构系统的形成提供了基础,强压实作用使得孔隙结构更加复杂化,研究成果为研究区下一步勘探及开发提供借鉴。

In view of the complex pore structure and unknown influencing factors of Chang 4+5_(2) tight sandstone reservoir in Heijiabao area of Ordos Basin,four types of pore structures were identified by means of logging,conventional physical properties,scanning electron microscopy,cast thin section and high-pressure mercury pressure testing.Among which Type I and Type II were preferred as exploration targets,and the results were applied to the exploration of Chang 4+5 reservoirs.The results show that the average porosity and permeability of Chang 4+5_(2) in the study area is 10.43%and 0.79×10^(-3) respectively,belonging to a typical dense sandstone reservoir with residual intergranular pores as the main space type,the pore throat scale is mainly nano-scale,followed by micron-scale,and the average pore throat radius is 0.02~10.00μm.The underwater distributary channels and estuarine dams with well-developed Type I and Type II have the best microfacies pore structures,making them key targets for exploration and development.Based on the evaluation results of reservoir pore structure,three types of exploration zones are divided in the study area as the preferred areas for exploration and development.The sedimentation of fine-grained sandstone provides the foundation for the formation of different pore structure systems of Chang 4+5_(2),and the strong compaction makes the pore structure more complex.The research results provide a good reference for the next exploration and development in the study area.