致密砂岩中岩屑溶蚀及其伴生胶结对孔隙发育的影响——以川东北元坝西部须二下亚段为例  

Effect of dissolution of rock fragments and its associated cementation on pore evolution: A case study of the lower sub-member of the second member of Xujiahe formation in the west of Yuanba area,northeastern Sichuan basin

作　　者：周志恒 钟大康[1,2] 凡睿[3] 王爱[1,2] 唐自成[1,2] 孙海涛 王威[3] 杜红权[3] ZHOU Zhiheng;ZHONG Dakang;FAN Rui;WANG Ai;TANG Zicheng;SUN Haitao;WANG Wei;DU Hongquan(College of Geosciences,China Univers让y of Petroleum (Beijing),Beijing 102249,China;National Laboratory of Oil and Gas Resources and Exploration,China University of Petroleum (Beijing),Beijing 102249,China;SINOPEC Exploration Company,Chengdu,Sichuan 610041,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [3]中国石化勘探南方分公司,四川成都610041

出　　处：《中国矿业大学学报》2019年第3期592-603,615,共13页Journal of China University of Mining & Technology

基　　金："十三五"国家科技重大专项(2016ZX05002)

摘　　要：本文旨在厘清致密砂岩储层成岩作用对孔隙发育的影响.以四川盆地东北元坝西部须二下亚段为例,采用铸体薄片、氩离子抛光及扫描电镜观察、NESE Geo图像分析和物性测试等手段分析岩石成分,确定成岩特征,获取孔隙度和渗透率值,认为岩屑溶蚀及其伴生胶结影响孔隙的垂向分布和发育程度.研究结果表明:元坝西部须二下亚段主要岩石类型为岩屑砂岩,在埋藏过程中,中成岩阶段发生岩屑溶蚀作用,孔隙度增加3.35%,产生的粒内溶孔成为储层主要孔隙类型.垂向上,岩屑溶蚀析出产物由溶蚀段向上覆及下伏储层迁移,由近及远沉淀绿泥石胶结物(其中发育绿泥石晶间微孔)、硅质胶结物(距溶蚀段2～3 m)及钙质胶结物(距溶蚀段3～4 m),导致储层孔隙度自溶蚀段起向上下逐渐降低.To clarify the influence of tight sandstone reservoirs diagenesis on pore evolution, this study focuses on the lower sub-member of the second member of Xujiahe formation in the west of Yuanba area, northeastern Sichuan basin of SW China. Methods such as the pore cast, argon ion polishing-scanning electron microscope, NESE Geo image analysis system and physical property test were used to analyze the rock composition, identify the diagenesis characteristics, obtain the values of porosity and permeability, observe the micropores, and determine the proportions of various types of pores. According to the analysis, the dissolution characteristics of rock fragments and its associated cementation have an effect on the vertical distribution of pores. The results show that the main rock type is lithic sandstone. In the middle diagenetic stage of burial, the rock fragments dissolution occurred, giving rise to the generation of intragranular dissolved pores, which became the main pore type in the reservoir, and the porosity was increased by 3.35%. In the vertical direction, the product of fragments dissolution migrated from the dissolution zone to the upper and the underlying reservoirs. Chlorite cement(where intercrystalline micropores are developed), siliceous cement(2-3 m away from the dissolution zone) and calcareous cement(3-4 m away from the dissolution zone) precipitated from the near to the distant, which resulted in a gradual decrease in reservoir porosity from the dissolution zone to the upper and the underlying reservoirs.

关 键 词：致密砂岩 岩屑溶蚀 孔隙演化 须二下亚段 元坝西部 川东北 

分 类 号：TE122.2[石油与天然气工程—油气勘探]