鄂尔多斯盆地东南部长6段致密砂岩孔喉结构及演化

doi:10.7657/XJPG20230605

摘要/Abstract

摘要：

通过铸体薄片、扫描电镜、全岩与黏土矿物X射线衍射、高压压汞、CT扫描等分析测试手段，对鄂尔多斯盆地东南部长6段非均质致密砂岩储集层的成岩-孔隙动态演化开展研究，在此基础上，讨论不同储集空间的成岩-孔喉演化特征。研究区长6段储集层的储集空间分为残余原生粒间孔主导型、溶蚀孔主导型和混合孔型3种；矿物成分和结构成熟度制约储集层的初始孔喉结构；胶结作用及其强度影响储集层的致密程度；溶蚀作用产生的孔喉影响储集性能。若储集层主要受压实作用和绿泥石胶结作用影响，则残余原生粒间孔占主导，孔隙孤立，多表现为中孔-疏网状喉道型储集空间，孔隙度较高，但连通性较差；若受浊沸石胶结和强溶蚀作用影响，则浊沸石溶蚀孔占主导，连通性好，多表现为中孔-类树状喉道型储集空间，为最佳储集空间；储集层经历绿泥石胶结、浊沸石胶结—弱溶蚀作用后，受浊沸石溶蚀孔与残余原生粒间孔共同影响，连通性较好，多表现为微孔、中孔-密网状喉道型储集空间，储集性能介于前两者之间。

关键词: 鄂尔多斯盆地, 延长组, 长6段, 致密砂岩储集层, 储集空间, 微观孔喉结构, 高压压汞, CT扫描

Abstract:

Based on the analyses of cast thin section, scanning electron microscopy (SEM), X-ray diffraction (XRD) of whole rock and clay minerals, high-pressure mercury intrusion, and CT scanning, a detailed study was conducted on the dynamic diagenesis-pore evolution of the Chang 6 heterogeneous tight sandstone reservoirs in the southeastern Ordos basin. Then the characteristics of diagenesis and pore-throat evolution of different reservoir spaces were discussed.The accommodation of Chang 6 reservoir in the study area is classified into 3 types such as reservoir spaces dominated by residual primary intergranular pores, dominated by dissolution pores, and mixed pores. The mineral composition and textural maturity control the initial pore-throat structure of the reservoir, cementation and its intensity influence the tightness of the reservoir, and the pore throats formed due to dissolution affect reservoir storage performance. If the reservoir is mainly affected by compaction and chlorite cementation, then residual primary intergranular pores are dominant, and the fractures are isolated, mostly leading to reservoir spaces consisting of mesopores with sparse reticular throats, indicative of good storage but poor connectivity. If the reservoir is influenced by zeolite cementation-strong dissolution, then zeolite dissolution pores are dominant, resulting in excellent pore throat connectivity, often appearing as reservoir spaces consisting of mesopores with tree-like throats, indicative of the optimal accommodation. If the reservoir has undergone cementation of chlorite, and cementation-weak dissolution of zeolite, both zeolite dissolution pores and residual primary intergranular pores contribute to relatively good pore throat connectivity, often exhibiting reservoir spaces consisting of micropores to mesopores with dense reticular throats, with the storage and transportation capacity falling between the above mentioned two.

Key words: Ordos basin, Yanchang formation, Chang 6 member, tight sandstone reservoir, reservoir space, microscopic pore-throat structure, high-pressure mercury intrusion, CT scanning

中图分类号:

TE122.2

严敏, 赵靖舟, 黄延昭, 杨振亚, 方越, 吴和源. 鄂尔多斯盆地东南部长6段致密砂岩孔喉结构及演化[J]. 新疆石油地质, 2023, 44(6): 674-682.

YAN Min, ZHAO Jingzhou, HUANG Yanzhao, YANG Zhenya, FANG Yue, WU Heyuan. Pore Throat Structure and Evolution in Chang 6 Tight Sandstone Reservoirs in Southeastern Ordos Basin[J]. Xinjiang Petroleum Geology, 2023, 44(6): 674-682.

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储集层类型	样品块数	渗透率/ mD	最大进汞饱和度/%	退汞效率/%	最大孔喉半径/μm	孔喉中值半径/μm	平均孔喉半径/μm	均质系数	特征结构系数
残余原生粒间孔主导型	88	0.097~1.070 （0.337）	76.23~92.37 （85.93）	13.66~47.92 （25.24）	0.09~5.25 （1.19）	0.04~0.26 （0.13）	0.01~0.59 （0.23）	0.09~0.75 （0.21）	0.13~0.99 （0.82）
溶蚀孔主导型	103	0.024~0.835 （0.510）	56.13~89.17 （79.88）	8.29~44.87 （21.06）	0.09~7.94 （1.27）	0.04~0.22 （0.14）	0.01~0.67 （0.20）	0.17~0.89（0.43）	1.42~18.37 （2.48）
混合孔型	71	0.020~1.284 （0.359）	46.83~96.08 （86.42）	13.93~43.29 （28.46）	0.09~2.80 （0.63）	0.03~0.20 （0.10）	0.01~0.33 （0.12）	0.02~0.46（0.12）	1.30~4.08 （1.69）

储集层类型	样品块数	碎屑颗粒			胶结物				粒度
储集层类型	样品块数	石英含量/%	长石含量/%	岩屑含量/%	绿泥石含量/%	浊沸石含量/%	硅质含量/%	方解石含量/%	粒度中值/ mm	分选系数
残余原生粒间孔主导型	88	22~32 （25）	40~58 （52）	0~9 （8）	3.9~14.8 （6.8）	0.4~4.8 （2.2）	0~3.1 （1.3）	0~2.0 （0.9）	0.01~0.40 （0.20）	1.20~1.51 （1.30）
溶蚀孔主导型	103	28~37 （32）	40~52 （44）	0~8 （5）	0~5.5 （1.6）	4.1~26.4 （11.1）	0~0.7 （0.5）	0~2.3 （0.9）	0.01~0.41 （0.22）	1.39~2.37 （1.69）
混合孔型	71	23~35 （27）	42~56 （48）	0~9 （7）	0~4.1 （3.7）	1.3~8.4 （4.2）	0~3.5 （1.9）	0~4.9 （2.5）	0.01~0.35 （0.18）	0.95~1.22 （1.02）