库车坳陷DB气田白垩系砂岩胶结作用及其与构造裂缝关系

以普通薄片和铸体薄片观察与鉴定为基础,辅以岩芯精细观察、阴极发光显微镜分析、扫描电镜分析、黏土矿物X衍射分析、包裹体分析、油层物性分析等技术手段,结合区域储层地质研究成果,系统研究塔里木盆地库车坳陷DB气田白垩系巴什基奇克组砂岩储层胶结作用特征及其发育期次,并剖析其与构造裂缝的关系.结果表明,DB气田白垩系砂岩为裂缝-孔隙型特低孔-特低渗储层,构造裂缝发育是储层高产的主要因素;储层胶结作用强烈,尤其以碳酸盐胶结为主,与黏土矿物转化有明显的因果关系,共发育“6 Ma之前”、“6~5 Ma”和“3~2 Ma”三期主要的胶结作用;多期次胶结作用与该区三期构造裂缝的有效性关系密切,只有错过主要胶结作用时期的第三期(N₂末)构造裂缝才是最有效的储集空间.

Cementation and Its Relationship with Tectonic Fractures of Cretaceous Sandstones in DB Gas Field of Kuqa Sub-basin

The cementation and its relationship with tectonic fractures of sandstone of Bashijiqike Formation of Cretaceous in DB gas field of Kuqa Sub-basin were researched through thin-section analysis, core observation, cathodoluminescence analysis, scan electricity microscope observation, X-ray diffraction, fluid inclusion and reservoir physical parameters analysis, etc and combining histories of tectonic development. It is recognized that the sandstone of Cretaceous in DB gas field is fracture-pore reservoir and with ultra-low porosity and ultra-low permeability. The developed fractures are the main factor of high production capacity. The sandstone has strong diagenesis and the main cements are authigenic carbonate minerals. The cementation and transformation of clay minerals have strong causal relationship. There are three cementation stages, which are “before 6 Ma”, “6~5 Ma” and “3~2 Ma”, respectively. Multi stage cementations are closely related to the validity of three stages tectonic factures in DB gas field. Only the third stage fracture (formed at the end of N₂) is the most effective reservoir space for missing completely main cementation.