特低渗砂岩储层微观结构及孔隙演化定量分析

来源期刊:中南大学学报(自然科学版)2011年第11期

论文作者:吴小斌 侯加根 孙卫

文章页码:3438 - 3446

关键词:特低渗储层;微观孔隙结构;成岩作用;孔隙演化;鄂尔多斯盆地

Key words:ultra-low permeability reservoir; micro-pore structure; diagenesis; porosity evolution; Ordos basins

摘    要:为了表征鄂尔多斯盆地姬塬地区长4+5油层组低孔特低渗长石砂岩的孔隙结构,进一步探讨孔隙演化及其控制因素,通过铸体薄片、扫描电镜、高压压汞、X线衍射、粒度分析及物性等资料,分析总结出5种孔隙类型和4种喉道类型;结合成岩作用研究,采用定性分析与定量计算的方法分析孔隙演化过程。研究区储层孔隙以粒间孔、长石溶孔和粒间溶孔为主,发育点状、缩颈状和片状喉道,喉道具有细喉和微细喉的特点。成岩缝的发育改善储层的渗透性,相互连通的微裂缝网络是流体运移的最佳通道。运用未固结砂岩原始孔隙度与砂岩的分选系数的统计关系,恢复计算出研究区砂岩原始孔隙度平均为34.60%。在成岩过程中,机械压实作用和胶结作用对储层孔隙具有中等程度破坏作用,受二者影响,未固结砂岩49.4%的原生粒间孔被压实损失,28.7%的孔隙被胶结破坏。区内溶蚀作用较发育,溶蚀强度中等,并形成大量次生孔隙,使得孔隙度增加到11.33%,溶蚀作用的孔隙增加率为11.0%,极大地改善低孔特低渗砂岩储层的储集空间。定量计算结果与定性认识的一致性以及与室内物性测试结果的吻合性表明:研究方法与结论可靠,这对于同类储层孔隙演化的研究具有借鉴意义。

Abstract: The average porosity of sandstone reservoir in Jiyuan area of Ordos basins is 11.68%, average permeability is 0.58×10-3μm2, belonging to the ultra-low permeability and low porosity reservoir. Ultra-low permeability sandstone reservoir has complex micro-structure, and research on porosity evolution is a hot-spot currently. Using casting thin sections, scanning-electron micro-scopes, granularity analysis and datum form high-pressure mercury injection and X-ray, five porosity types and four throat types were analyzed and summarized. Pores evolution was researched by qualitative analysis and quantitative calculation lastly. The dominating pore type of Chang 4+5 reservoirs is inter-granular pore and feldspar-dissolved pore. The throat types are point-shaped throat, necked throat, flake throat. The micro-fractures improve permeability and become the best channel in the reservoir. Using statistical relationship between original porosity and sorting coefficient, the reservoir sandstones original are restore calculated and the average is 34.60%. Dynamics has a major impact to characteristics of pore evolution. The impact of compaction is greatest and its loss-rate of porosity is 49.4%, and the loss-rate of porosity of cementation is 28.7%. The dissolution of the reservoir sandstone improves porosity about 3.75%. Quantitative calculation result and qualitative knowledge have consistency, and are inosculated to experimental data. It is shown that the research methods and results are reliability, and have significance to similar reservoir.

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