合水—华池地区长7油层组相对高孔渗成因分析

Cause analysis of higher porosity and permeability reservoir group in Chang 7,
Heshui￣Huachi Region

黄囿霖 陈世加 姚宜同 张潇文 王力

西南石油大学地球科学与技术学院，四川 成都 610500

School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China

鄂尔多斯盆地合水—华池地区延长组长7油层组属于盆地半深湖—深湖沉积体系，除发育良好的烃源岩外，因西南方向河流的注入，该区有大面积湖泊浊积扇砂体分布，岩石类型以岩屑质长石杂砂岩和长石质岩屑杂砂岩为主，压实作用强，物性差，属于超低孔超低渗致密砂岩，但致密背景下发育有利于油气富集的“相对高孔渗”砂岩储层。针对相对高孔渗问题，结合盆地地质背景，展开了沉积相、成岩作用及异常压力的研究。研究中采用了岩石薄片观察、恒速压汞和剩余压力分析等方法，认为相对高孔渗影响因素有：1）岩石组分、分选和沉积相带对储层的控制；2）成岩过程中石英次生加大、绿泥石包膜和烃类早期充注对原生孔隙的保护以及有机酸溶蚀次生孔隙的形成；3）生烃增压、差异压实、黏土矿物成岩和热力作用产生的异常高压对于储层的改造。

The Chang 7 reservoir group, Yanchang Formation of Heshui￣Huachi Region, Ordos Basin belongs to half deep lake and deep lake sedimentary system. With the well-developed hydrocarbon source rocks and influx from the river of southwest, there is a large area of turbidity sand body distribution. Rock types are mainly lithic feldspar graywacke and feldspathic lithic greywacke. With strong compaction and poor physical property, tight sandstone with low porosity and permeability was formed, which was favorable to the enrichment of higher porosity and permeability reservoir group. Based on the basin′s geological background, sedimentary facies, diagenesis and abnormal pressure were researched to address the high porosity and permeability problem. In the research, thin section observation, rate-controlled mercury penetration and residual pressure were used. The relatively high permeability influence factors are concluded: the rock components, sorting and sedimentary facies control of reservoir; primary pore are protected by quartz overgrowth diagenetic process, chlorite coated and early hydrocarbon filling, secondary pore are formed by organic acid dissolution; abnormal high pressure formed by hydrocarbon generation pressurization, different compaction, clay mineral rock, thermal and tectonic dynamics can reconstruct reservoir.

10.6056/dkyqt201601009