陇东油区长8含油砂岩成岩过程中的孔隙度演化

 利用铸体薄片、X-射线衍射、扫描电镜、物性等资料，分析陇东油区长8 含油砂岩成岩作用和孔隙度演化过程。研究表明，含油砂岩处于中成岩阶段A 期，经历的强压实、胶结及弱溶解作用是其致密化的控制性因素，其中压实孔隙损失率为38.9%，胶结孔隙损失率为38.0%，而溶蚀孔隙度仅为3.9%。孔隙度演化分析表明，含油砂岩的初始孔隙度为37.3%，早成岩阶段的压实和胶结作用后剩余原生粒间孔隙度为17.9%；中成岩阶段的第1 期油气充注时孔隙度仍高达17.0%，第2 期油气充注时孔隙度仅为12.5%，说明含油砂岩在两期油气充注之间的成岩过程中成为致密砂岩储层。

Porosity Evolution During Diagenesis of Oil-bearing Sandstone in Chang 8 of Longdong Oil-producing Region

The diagenesis and porosity evolution of the oil-bearing sandstone in Chang 8 of Longdong oil-producing region are analyzed by means of casting thin-sections, X-ray diffraction data, scanning electron micrograph observation and physical properties. The oil-bearing sandstone is currently at the first stage of the middle-diagenesis period. It went through strong compaction and violent cementation and weak dissolution, which led to the tight sandstone reservoir. The porosity loss rate of the compaction is 38.9%, the porosity loss rate of the cementation is 38.0%, and the porosity of the dissolution is only 3.9%. The porosity evolution during the diagenesis shows that the primary porosity is 37.3%, the residual intergranular porosity after the compaction and the cementation of the early diagenesis process is 17.9%, the porosity of the first oil charging process is 17.0%, and the porosity of the second oil charging process is only 12.5%, which illustrates that the densification of the oilbearing sandstone occurred between the first oil charging process and the second oil charging process of the middle-diagenesis period.