板桥凹陷深层扇三角洲前缘优质储集层特征及控制因素——以沙河街组为例

Characteristics and controlling factors of high-quality reservoirs in deep fan delta front of Banqiao sag:Taking Shahejie formation as an example

综合利用岩心、铸体薄片、扫描电镜、生产动态等资料,对板桥凹陷沙河街组深层储集层特征、主控因素进行了分析。研究区深层储集层以岩屑长石砂岩、长石岩屑砂岩为主,孔隙类型主要为粒间溶孔、粒内溶孔及颗粒铸模孔;机械压实、胶结作用是储集层物性变差的主要因素,酸性介质主导的溶蚀作用增加孔隙,而超压作用保护孔隙。研究表明深层储集层形成是"构造-沉积-成岩"多因素相互耦合作用的结果。深凹区紧邻油源断层的水下分流河道微相砂体粒度粗、原始孔隙条件好,酸性流体易于进入并形成次生溶孔,后期油气充注及其导致的异常高压抑制了胶结等减孔成岩作用,为"强溶蚀-弱胶结"成岩相,发育一定规模的中高孔-中高渗储集层,是深层油气勘探开发的潜力目标区。

Data of core,casting thin section,scanning electron microscope and production performance are comprehensively used to analyze the deep reservoir characteristics and main controlling factors of Shahejie formation in Banqiao sag.The deep reservoirs in the study area are mainly lithic graywacke and feldspathic litharenite.The pore types are mainly intergranular,intragranular dissolved pores and particle mold pore.Mechanical compaction and cementation are the major factors for the deterioration of the physical properties of the reservoir.The dissolution dominated by the acidic medium increases the pores,while the overpressure protects pores.The study shows that the formation of deep reservoir is the result of the coupling of structure-sedimentation-diagenesis and other factors.In the deep sag area,the subaqueous distributary channel microfacies sand bodies adjacent to oil sources fault have coarse grain size and good original pore conditions,acidic fluids is easy to enter and form secondary dissolved pores,late oil and gas filling and its resulting abnormal high pressure inhibit cenmentation and other pore-reducing diagenesis.It is a strong dissolution-weak cementation diagenetic facies and develops a certain scale of medium-high porosity-medium-high permeability reservoirs,which is a potential target area for deep oil and gas exploration and development.