川东北地区须二段石英砂岩储层特征差异性

利用岩屑薄片鉴定、岩心观察、砂岩粒度概率统计、物性分析等资料，探讨形成川东北元坝和马路背2个地区须家河组第二段石英砂岩储层的物源方向、沉积条件、成岩作用及构造断裂系统的特征差异。结果表明川东北地区须二段石英砂岩储层普遍受物源、沉积、成岩和构造应力等联合控制，不同地区由于基础地质条件不同其储层发育特征也随之不同。元坝地区须二段石英砂岩储层较马路背地区更致密，其沉积期经过滨岸湖水反复淘洗作用导致易溶矿物缺失，加之成岩期强压实作用的影响，形成了相对低孔低渗型储层；而马路背地区须二段石英砂岩储层物性较好，测试开发效果也优于元坝地区，属于相对高孔高渗型储层。主要由于马路背地区靠近物源区，储层砂体中保留了部分不稳定矿物，且该地区构造活动强烈，微裂缝发育，利于后期溶蚀与破裂作用对储层的改造。

Differences of quartz sandstone reservoir characteristics for the Member 2 of Xujiahe Formation in Northeast Sichuan Basin,China

Differences of provenance direction,depositional condition,diagenesis and fracture fault system and characteristics between the quartz-sandstone reservoirs of Member 2 of Upper Triassic Xujiahe Formation in the area of Yuanba and Malubei area of northeast Sichuan are studied by means of debris section identification,core observation,sandstone grain size probability statistics and physical characteristic analysis.It shows that the Member 2 of Xujiahe Formation in the area is controlled by provenance, deposition, digenesis and structural pressure. The characteristics of reservoir development are different due to different geological conditions in different areas.The quartz-sandstone reservoirs of Member 2 of Xujiahe Formation in the area of Yuanba is more denser than that in Malubei because the depositional stage here is affected by the repeated wash effect of shore lake water and resulted in the absence of soluble mineral and the early stage strong compaction digenesis lead to the formation of low permeability and low porosity reservoir.While the quartz-sandstone reservoirs of Member 2 of Xujiahe Formation in the area of Malubei has better physical characteristics with favorable testing and exploiting effects and belongs to relatively high permeability and high porosity reservoir.It considered that the Malubei area is closer to the provenance indicated by appearance of some unstable minerals in the reservoir sand bodies.In the Malubei area,late stage relatively strong structural activity bring in the development of micro-fractures which are good condition for later digenesis modifications such as corrosion and fracture.