川东北元坝地区须家河组储层特征与超致密成因探讨

发布时间：2018-05-27 07:22

本文选题：岩石组分 + 孔隙结构　；参考：《地质学报》2017年09期

【摘要】：元坝地区须家河组砂岩的致密化程度极高,以超低孔、超低渗储层为主,属于超致密砂岩。本文基于铸体薄片、阴极发光、扫描电镜和物性等资料,在对砂岩的岩石组分、孔隙类型及物性特征分析的基础上,通过与国内外典型致密砂岩对比,揭示研究区砂岩较其他砂岩致密化程度高的原因,分析超致密砂岩的勘探潜能。结果表明,研究区砂岩具有较高的塑性岩屑、碳酸盐岩岩屑和黏土杂基含量;填隙物以黏土杂基和钙质胶结物为主,较强的硅质胶结作用仅发育于石英砂岩中。孔隙多为黏土杂基晶间微孔,喉道呈窄缝状或不发育,孔喉分选差,偏细歪度。砂岩致密化程度高主要有两方面的原因:一是原始组构差,成分成熟度低,含有较高的塑性岩屑、碳酸盐岩岩屑和黏土杂基含量,导致砂岩在早成岩阶段既已经历了很强的压实作用和钙质胶结作用,致密化时间早,溶蚀作用不发育;二是成岩演化阶段高,砂岩经历了中成岩阶段的压溶及进一步的钙质/硅质胶结,使得砂岩超致密化。与国内外典型致密砂岩气藏对比表明,超致密砂岩有效孔隙少,对天然气的富集能力有限。元坝地区须家河组只有孔隙度近于8%(如长石岩屑砂岩)的砂岩才可成为有利的致密气储层。
[Abstract]:The sandstone of Xujiahe formation in Yuanba area is highly densified, which is mainly composed of ultra-low porosity and ultra-low permeability reservoirs. Based on the data of thin cast sheet, cathode luminescence, scanning electron microscope and physical properties, this paper analyzes the rock composition, pore type and physical properties of sandstone, and compares them with typical compact sandstone at home and abroad. The reason why sandstone densification degree is higher than other sandstone in the study area is revealed, and the exploration potential of super tight sandstone is analyzed. The results show that the sandstone in the study area has high plastic lithology, carbonate lithology and clay complex, and the intercalation is dominated by clay complex and calcareous cementation, and the strong siliceous cementation is only developed in quartz sandstone. The pores are mostly intergranular micropores of clay, the throat is narrow or undeveloped, and the pore throat is poor in sorting and slanting degree. There are two main reasons for the high densification of sandstone: first, the original texture is poor, the composition maturity is low, and the sandstone contains high plastic cuttings, carbonate rock debris and clay complex base content. In the early diagenesis stage, the sandstone has experienced strong compaction and calcareous cementation, early densification time and undeveloped dissolution, and high diagenetic evolution stage. The sandstone experienced pressure solution and further calcareous / siliceous cementation in the middle diagenetic stage, which made the sandstone super dense. The comparison with typical tight sandstone gas reservoirs at home and abroad shows that the super-tight sandstone has less effective pores and limited ability to enrich natural gas. The Xujiahe formation in Yuanba area can become a favorable tight gas reservoir only if the porosity is close to 8% (for example, feldspar lithic sandstone).
【作者单位】：中国石油大学(北京)油气资源与探测国家重点实验室;中国石油大学(华东)地球科学与技术学院;
【基金】：国家自然科学基金项目(编号41472118)资助成果
【分类号】：P618.13

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