准噶尔盆地永进地区齐古组深埋砂岩成岩作用对储集层质量影响的定量表征^*

Quantitative characterization of influence of diagenesis on reservoir quality of deep-buried sandstone of the Qigu Formation in Yongjin area,Junggar Basin

摘要

永进地区侏罗系齐古组是准噶尔盆地腹部一套重要的深埋含油层系,现今埋深5400~6100 m,其储集层质量控制了油气储量和产量。运用铸体薄片、阴极发光、扫描电镜、物性、XRD全岩和黏土矿物分析等资料对齐古组深埋砂岩储集层成岩演化过程开展研究,建立成岩演化序列,定量表征不同成岩作用对储集层质量的影响,结合区域埋藏史、油气充注史,最终明确储集层成岩演化过程。永进地区齐古组储集层岩性主要为长石质岩屑砂岩和岩屑砂岩, 杂基含量低,胶结物类型主要为碳酸盐矿物、硅质和黏土矿物,具成分成熟度低而结构成熟度高的特征; 储集空间类型以剩余原生粒间孔和粒间溶孔为主; 整体处于中成岩A期阶段,储集层孔隙度变化主要受压实、胶结、溶蚀作用控制,压实作用和胶结作用是造成储集层减孔的主要成岩因素,分别造成原生孔隙损失率为65.98%和21.80%,溶蚀作用增加了5.25%的孔隙度,起到了有效改善储集层物性的作用。综合研究认为,永进地区齐古组储集层成岩演化主要受沉积环境、成岩作用、埋藏史、油气充注4大因素共同控制,成岩作用起到改造储集层物性的作用,是导致储集层非均质性较为明显的决定性因素。

Abstract

The Jurassic Qigu Formation in the Yongjin area is a set of important oil-bearing strata in the central Junggar Basin. It is a typical deep-buried sandstone reservoir with a burial depth of 5400~6100 m,and its reservoir quality controls oil and gas reserves and production. In this paper,the diagenetic evolution process of deep-buried sandstone reservoirs in the Qigu Formation is studied by using the data of cast thin section,cathodoluminescence,scanning electron microscopy,XRD whole rock and clay mineral analysis. A diagenetic sequence is established,and the impacts of various diagenetic processes on reservoir quality are quantitatively assessed,integrating regional burial and hydrocarbon charge histories to delineate the reservoir’s diagenetic evolution. The lithology of the Qigu Formation reservoir in the Yongjin area is mainly composed of feldspathic lithic sandstone and lithic sandstone. The cement includes mainly carbonate minerals,siliceous minerals and clay minerals with low composition maturity and high texture maturity. The reservoir space types are mainly the remaining primary intergranular pores and secondary intergranular dissolved pores. Overall,the reservoir porosity changes are mainly controlled by compaction,cementation and dissolution,which are the main diagenetic factors reducing reservoir porosity,resulting in primary pore loss rates of 65.98% and 21.80% respectively. Dissolution increases the porosity by 5.13%,which effectively improves the physical properties of the reservoir. The comprehensive study shows that the diagenetic evolution of the Qigu Formation reservoir in the Yongjin area is mainly controlled by four factors: sedimentary environment,diagenesis,burial history and oil and gas charging. Diagenesis plays a role in the transformation of reservoir physical properties and is the critical determinant of the observed reservoir heterogeneity.

关键词

定量表征 / 成岩作用 / 孔隙演化 / 深部储集层 / 齐古组 / 永进地区

Key words

quantitative characterization / diagenesis / pore evolution / deep reservoir / Qigu Formation / Yongjin area

基金资助

*国家自然科学基金项目(编号: 42272110)资助