歧北斜坡沙二段储层碱性环境成岩演化及其对储集性能的影响

doi:10.3969/j.issn.1006-6535.2023.03.005

摘要/Abstract

摘要： 为深化认识歧北斜坡沙二段储层成岩环境、演化模式及孔隙发育机理,通过岩石(铸体)薄片、扫描电镜、X射线衍射分析等手段,对沙二段致密砂岩储层碱性环境成岩作用特征、成岩演化模式、碱性环境成因机制及其对储层孔隙发育的影响进行研究。结果表明:储层中存在石英溶蚀、多期碳酸盐矿物胶结交代、硬石膏交代以及碱性黏土矿物组合等多种碱性环境的成岩现象;目前储层成岩阶段处于中成岩A₂亚期,整个成岩演化过程中,成岩环境经历了碱性—酸性—碱性的变化;早期成岩阶段,碱性成岩环境的形成与同沉积期的咸水湖盆环境密切相关,中成岩A₂亚期阶段,由于金属阳离子富集,酸性水来源减少并大量消耗,导致孔隙水介质pH值升高,重新恢复为碱性成岩环境;碱性环境形成的多期碳酸盐胶结物大量充填孔隙,使储集空间大幅降低,同时,储层中的早期碱性流体介质也抑制了酸性流体对储层的溶蚀改造强度,但碱性环境下石英溶蚀形成了大量次生孔隙,是研究区储层孔隙发育的主要机制。研究成果对预测研究区优质储层分布具有指导意义。

关键词: 储层孔隙, 成岩演化, 石英溶蚀, 碱性环境, 储集性能, 岐北斜坡

Abstract: In order to deepen the understanding of the diagenetic environment, evolution mode and pore development mechanism of the reservoir in the Second Member of Shahejie Formation of Qibei Slope, the characteristics of alkaline environmental diagenesis, diagenetic evolution mode, alkaline environmental genesis mechanism and its influence on pore development of the dense sandstone reservoir in the Second Member of Shahejie Formation were studied by means of rock (cast) thin section, scanning electron microscopy and X-ray diffraction analysis. The results show that there are various alkaline environment diagenesis phenomena in the reservoir, such as quartz dissolution, multi-phase carbonate mineral cementation and metasomatism, anhydrite metasomatism and alkaline clay mineral assemblage; the current reservoir diagenctic stage is in the mesogenetic A₂ sub-stage, and the diagenetic environment has experienced alkaline-acidic-alkaline changes during the whole diagenetic evolution; in the early diagenetic stage, the formation of the alkaline diagenetic environment was closely related to the saltwater lake basin environment in the same sedimentary stage. In the mesogenetic A₂ sub-stage, due to the enrichment of metal cations, the acidic water source was reduced and heavily depleted, resulting in the increase of the pH value of the pore water medium and a return to the alkaline diagenetic environment; the multi-phase carbonate cement formed in the alkaline environment filled the pores in large quantities, which significantly reduces the reservoir space, and at the same time, the early alkaline fluid medium in the reservoir also suppressed the dissolution modification intensity of the acidic fluid to the reservoir, but the quartz dissolution in the alkaline environment formed a large number of secondary pores, which is the main mechanism of pore development in the reservoir within the study area. The research results are of guiding significance for predicting the distribution of high-quality reservoirs in the study area.

Key words: reservoir pore, diagenetic evolution, quartz dissolution, alkaline environment, reservoir performance, Qibei slope

中图分类号:

TE122

刘金库, 邓明杰, 张泽, 李国良, 房金伟, 汪春浦, 王飞洋, 谭荃. 歧北斜坡沙二段储层碱性环境成岩演化及其对储集性能的影响[J]. 特种油气藏, 2023, 30(3): 38-46.

Liu Jinku, Deng Mingjie, Zhang Ze, Li Guoliang, Fang Jinwei, Wang Chunpu, Wang Feiyang, Tan Quan. Influence of Alkaline Environment Diagenetic Evolution on Reservoir Performance in the Second Member of Shahejie Formation of Qibei Slope[J]. Special Oil & Gas Reservoirs, 2023, 30(3): 38-46.

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