大牛地气田下石盒子组致密砂岩储层成岩演化

Diagenetic evolution of tight sandstone reservoir in lower Shihezi formation from Daniudi gas field

综合岩石薄片、扫描电镜、阴极发光、流体包裹体及激光拉曼光谱等实验技术,对大牛地气田下石盒子组致密砂岩储层成岩作用类型及特征进行研究,精细刻画成岩作用活动期次,对储层成岩演化过程进行阶段划分,探讨储层致密化过程与烃类流体多期充注的次序关系。研究结果表明:大牛地气田下石盒子组致密砂岩储层以中砂岩为主,岩石类型以岩屑砂岩、岩屑石英砂岩为主;强压实、强硅质胶结、碱性溶解是下石盒子组致密砂岩储层的总体成岩面貌,胶结作用是引起储层致密化的主要原因,可细分出3期硅质胶结与2期钙质胶结;储层的成岩演化过程可依次划分为快速压实、酸碱交替、致密化和致密后4个阶段,储层成岩演化过程中存在3期含烃流体充注,含烃流体充注时间早于储层完全致密化时期,储层总体呈"先成藏—后致密"的特征。

The diagenesis types and characteristics of the tight sandstone reservoir in lower Shihezi formation from Daniudi gas field were studied by means of many experimental technologies, such as chip observation, scanning electron microscope, cathodoluminescence, fluid inclusions, laser raman spectroscopy and so on. The diagenesis activity times and diagenetic evolution process were divided. The order relationship between the reservoir densification process and multiphase hydrocarbon fluid filling was discussed. The results show that the sandstone reservoir of lower Shihezi formation is mainly medium sandstone and the rock types are mainly lithic sandstone and lithic quartz sandstone. Strong compaction, strong siliceous cementation and alkaline dissolution are the general diagenetic features of the tight sandstone reservoir in lower Shihezi formation. Cementation can be subdivided into three periods of siliceous cementation and two periods of calcareous cementation, and cementation is the main cause of reservoir densification. Diagenetic evolution process of the reservoir can be divided into four stages, i.e., fast compact stage, acidic and alkaline alternate stage, intense cement stage and the late transform stage. Hydrocarbon fluid filling exists in the three stages of the diagenetic evolution process. The time of hydrocarbon fluid filling is earlier than the period of reservoir densification. Overall reservoir has the characteristics of ＂hydrocarbon accumulation comes first and then reservoir densification＂.