廊固凹陷河西务构造带沙四段低渗储层特征及其成因机制

Characteristics and genetic mechanism of low-permeability reservoirs of the 4th member of Shahejie formation in Hexiwu structural zone of Langgu sag

通过薄片鉴定、物性测试、压汞测试等化验资料分析,结合镜下薄片观察和包裹体测温,采用地质历史时期储层物性反演的方法,对廊固凹陷河西务构造带沙四段储层特征及成因机制进行研究。结果表明:廊固凹陷河西务构造带沙四段储层属低孔特低渗储层,沉积作用差异是低渗透形成的根本原因,不同沉积作用形成的储层物质组成、粒度、分选不同,导致储层原始物性发生分异;成岩作用是低渗透形成的关键,成岩早期的快速压实、成岩中后期胶结物充填以及缺少有效的增孔和保孔机制最终导致低渗储层的形成;运用地质历史时期物性反演的方法建立储层物性演化史,能定量重现孔隙度和渗透率的演化过程。

Based on the data of thin section observation, geophysical property test, mercury injection test and fluid-inclusion tem- perature test, the characteristics and genetic mechanism of low-permeability reservoirs of the fourth member of Shahejie formation （Es4 ） in Hexiwu structural zone of Langgu sag were studied by using the inversion method of the reservoirs porosity and permeabil- ity during the geological history. The results show that there are low porosity and extremely-low permeability reservoirs in Es~ of Hexiwu structural zone. The sedimentary difference, which leads to different primary geophysical properties because of different material composition, grain size and sort, is the primary cause of low permeability. The diagenesis is the vital cause of low permea- bility. The rapid burial in early diagenetic stage, the cementation in later diagenetic stage and the lack of effective mechanism for increasing porosity and protecting pores form the low-permeability reservoirs finally. The method for inversion of the reservoirs＇ geo- physical property during the geological history can rebuild the evolutionary process of porosity and permeability.