柴达木盆地马海东地区古近系砂岩储层微观孔隙结构特征及微观致密区成因  

Micro-pore structure characteristics of the Paleogene sandstone reservoirs and genesis of microscopic tight zones in the Mahaidong area,Qaidam Basin

作　　者：阮壮[1] 徐睿 王杰[1] 常秋红 王大华[2] 王建东[2] 周广清[2] 于炳松[1] RUAN Zhuang;XU Rui;WANG Jie;CHANG Qiuhong;WANG Dahua;WANG Jiandong;ZHOU Guangqing;YU Bingsong(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Shengli Oilfield Branch Company,SINOPEC,Dongying,Shandong 257001,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国石化胜利油田分公司,山东东营257001

出　　处：《石油与天然气地质》2024年第4期1032-1045,共14页Oil & Gas Geology

基　　金：国家自然科学基金项目(42272136,42102162);中国石化胜利油田分公司科技攻关项目(30200384-21-ZC0613)。

摘　　要：柴达木盆地北缘马海东地区古近系的油气勘探已经取得发现,但储层微观孔隙结构特征认识不清是影响油气勘探与开发的主要因素之一。为揭示马海东地区古近系砂岩储层微观特征,综合运用岩石薄片显微镜观察、X射线衍射(XRD)分析和压汞测试等试验技术,开展了低渗透砂岩储层的岩石学特征、物性特征、微观孔隙结构及各储层非均质性对比研究,用变异系数定量表征了储层非均质强弱程度。研究结果表明:①古近系砂岩储层以长石岩屑砂岩为主,填隙物主要为方解石。②路乐河组Ⅰ砂组储层孔隙度较大,下干柴沟组Ⅱ砂组储层孔隙度中等,路乐河组Ⅱ砂组储层孔隙度最小。③储层岩石经历了压实、胶结和溶蚀成岩作用,路乐河组Ⅱ砂组储层非均质性最强,路乐河组Ⅰ砂组储层非均质性最弱,下干柴沟组Ⅱ砂组储层非均质性介于两者之间。④富塑性岩屑纹层或富杂基的低渗砂岩为致密储层,方解石胶结和塑性黏土质岩屑变形是致密储层形成的重要原因。Discoveries have been made in the Paleogene hydrocarbon exploration in the Mahaidong area on the northern margin of the Qaidam Basin.However,the current productivity is low primarily due to the limited understanding of the characteristics of micro-pore structures,restricting hydrocarbon exploration and exploitation in the area.To reveal the microscopic characteristics of the Paleogene sandstone reservoirs in the Mahaidong area,we investigate the petrology,physical property characteristics,micro-pore structures,and heterogeneity of low-permeability sandstone reservoirs in the Mahaidong area using techniques such as the micro-petrographic observation,X-ray diffraction(XRD)analysis,and highpressure mercury injection(MICP)experiments.Additionally,we quantitatively characterize the degree of reservoir heterogeneity using the coefficient of variation.The findings reveal that the Paleogene sandstone reservoirs consist primarily of feldspathic litharenites,with calcite identified as primary interstitial fillings.The porosity of the reservoirs decreases in the order of sandstone memberⅠof the Lulehe Formation,sandstone memberⅡof the Lower Ganchaigou Formation,and sandstone memberⅡof the Lulehe Formation.The reservoir rocks have undergone diagenetic processes such as compaction,cementation,and dissolution.Consequently,the reservoir heterogeneity decreases in the order of sandstone memberⅡof the Lulehe Formation,sandstone memberⅡof the Lower Ganchaigou Formation,and sandstone memberⅠof the Lulehe Formation.Low-permeability sandstones rich in plastic detrital lamina or matrix are identified as tight reservoirs,with calcite cementation and deformation of plastic clayey debris as the predominant factors contributing to reservoir tightness.

关 键 词：储层非均质性 微观孔隙结构 低渗透砂岩储层 古近系 马海东地区 柴达木盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]