致密砂岩中多期碳酸盐胶结物形成机理——以鄂尔多斯盆地华庆地区三叠系延长组长6_3为例  

The formation mechanism of multi-stage carbonate cements in tight sandstone: A case study of Chang 6_3 sub-member of Triassic Yanchang Formation in Huaqing area,Ordos Basin

作　　者：庞军刚 国吉安 杨友运 东玉 尚晓庆 王桂成 李谦 PANG Jungang;GUO Ji＇an;YANG Youyun;DONG Yu;SHANG Xiaoqing;WANG Guicheng;LI Qian(School of Earth Science and Engineering/Xi＇an Shiyou University, Xi＇an 710065, Shaanxi, China;No.2 Comprehensive Geophysical Exploration Research Party;Bureau of Geology and Mineral Resources Exploration and Development of Shaanxi, Xi＇an 710016, Shaanxi, Chin)

机构地区：[1]西安石油大学地球科学与工程学院,陕西西安710065 [2]陕西省地质矿产勘查开发局第二综合物探大队,陕西西安710016

出　　处：《地质通报》2018年第5期930-937,共8页Geological Bulletin of China

基　　金：国家科技重大专项<大型油气田及煤层气开发>(编号:2016ZX05050006);西安石油大学"沉积学与储层地质学"科研创新团队(编号:2013KYCXTD03);陕西省教育厅专项科学研究计划<鄂尔多斯盆地南部上古生界物源分析及砂体展布规律研究>(编号:17JK0605);中国地质调查局项目<鄂尔多斯周缘盆地群油气基础地质调查>(编号:121201011000150014)

摘　　要：为明确致密砂岩中碳酸盐胶结物的类型、分布特征及其形成机理,以鄂尔多斯盆地华庆地区延长组长63致密砂岩为例,在铸体薄片、阴极发光、扫描电镜分析的基础上,从岩石学、地球化学的角度进行分析。研究表明,碳酸盐胶结物主要有方解石、铁方解石、白云石和铁白云石,在不同地区分布类型差别较大,西南部含量较高,东北部含量较低,其含量、类型与物源及水介质中钙离子的来源有关,可分为内源及外源成因,由于晚期碳酸盐胶结物发育,较大规模地堵塞了孔隙,且后期溶解作用较差,成为长63砂岩致密化的一个重要因素。在绘制研究区铁方解石和铁白云石胶结物等值线图的基础上,认为研究区碳酸盐胶结物主要为碳酸盐岩屑溶解-再沉淀、长石溶解-再沉淀等形成机理。研究成果可为华庆地区延长组致密油储层有利区预测提供依据。In order to understand tight sandstone characteristics and formation mechanism, the authors analyzed the distribution and formation mechanism of carbonate cements in terms of petrological and geochemical characteristics of the samples by means of casting thin sections, cathodoluminescence and scanning electron microscopy in the samples, take the Chang 6_3 sub-member reservoir of Triassic Yanchang Formation in Huaqing area of Ordos Basin as the study object. The result shows that the main types of carbonate minerals are calcite,ferrocalcite,dolomite and ferrodolomite, and different areas show great difference in type distribution, being higher in content in southwest and lower in northeast. The content and type are related to the provenance and the source of calcium ions in aqueous medium,which can be divided into authigenic carbonate and exogenous carbonate. As the pore volume was plugged up by the carbonate cement on a large scale and the later dissolution was lacking,the sandstone of Chang 6_3 sub-member of Yanchang Formation became densified. On the basis of drawing the contour map of ferrocalcite and ferrodolomite cement in study area, the mecha-nism of carbonate cements was investigated. It is held that the carbonate cements were mainly formed by the dissolution-reprecipitation of carbonate rock debris and feldspar dissolution–precipitation. The results obtained by the authors can provide reference for favorable prediction of tight oil of Yanchang Formation in Huaqing area, and can also provide reference for microscopic characteristics study of tight hydrocarbon reservoir both in China and abroad.

关 键 词：碳酸盐 多期次 形成机理 致密砂岩 鄂尔多斯 华庆地区 延长组 

分 类 号：P534.51[天文地球—古生物学与地层学] P588.212.3[天文地球—地质学]