川中地区侏罗系沙溪庙组二段富钙地层水成因及其对天然气运聚的指示意义  

Origin of calcium-rich formation water and its implications for natural gas migration and accumulation in the 2nd member of the Jurassic Shaximiao Formation,central Sichuan Basin

作　　者：杨跃明[1] 王茂云 吴长江[1] 曾溅辉[2,3] 潘珂 张欢乐 王小娟[1] 陈冬霞[2,3] 崔虎旺 YANG Yueming;WANG Maoyun;WU Changjiang;ZENG Jianhui;PAN Ke;ZHANG Huanle;WANG Xiaojuan;CHEN Dongxia;CUI Huwang(Research Institute of Exploration and Development,Southwest Oil&Gasfield Company,PetroChina,Chengdu,Sichuan 610041,China;State Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;Research Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China)

机构地区：[1]中国石油西南油气田分公司勘探开发研究院,四川成都610041 [2]油气资源与工程全国重点实验室中国石油大学(北京),北京102249 [3]中国石油大学(北京)地球科学学院,北京102249 [4]中国石油新疆油田分公司勘探开发研究院,新疆克拉玛依834000

出　　处：《石油与天然气地质》2025年第1期178-191,共14页Oil & Gas Geology

基　　金：中国石油西南油气田公司科研项目(JS2022-003)。

摘　　要：基于34口井的地层水地球化学数据、含气饱和度数据和岩矿资料,分析了川中地区侏罗系沙溪庙组二段(沙二段)富钙地层水成因,探讨了地层水对源-储分离型致密砂岩气运聚的指示意义。研究结果表明:川中地区沙二段地层水较中国其他致密砂岩气藏具有明显的“钙富集和钠亏损”的特征。地层水矿化度为3.3~45.6 g/L,为CaCl_(2)型,Ca^(2+)当量比[γ(Ca^(2+))]为24.7%~69.5%。根据γ(Ca^(2+))将研究区沙二段地层水划分为高钙地层水[γ(Ca^(2+))≥60%]、中钙地层水[40%≤γ(Ca^(2+))<60%]和低钙地层水[γ(Ca^(2+))<40%]3种类型。3类地层水的化学特征和分布存在明显的差异:高钙地层水主要分布在距角①断裂相对较近且与角①断裂连通的河道砂组,矿化度平均值为34.1 g/L,相对较高,阳离子以Ca^(2+)为主,钠氯系数、脱硫酸系数和碳酸盐平衡系数最小;低钙地层水主要分布在距角①断裂较远或不与角①断裂直接连通的河道砂组,矿化度平均值为3.9 g/L,阳离子以Na^(+)为主,钠氯系数、脱硫酸系数和碳酸盐平衡系数最大;中钙地层水矿化度平均值为17.7 g/L,Na^(+)与Ca^(2+)含量相差不大,钠氯系数、脱硫酸系数和碳酸盐平衡系数介于前两者之间。Ca^(2+)含量较高的须家河组地层水的混入是沙二段地层水富钙的主要原因,后续的水-岩相互作用,尤其是斜长石的钠长石化导致钙进一步富集,而钠减少。川中地区沙二段地层水碳酸盐平衡系数、矿化度以及γ(Ca^(2+))沿着天然气侧向运移路径逐渐减少,表明富钙地层水化学指标对源-储分离型致密砂岩气藏具有较好的示踪能力。沙二段地层水中的钙越富集,储层的含气性越好,说明富钙地层水对天然气的富集具有指示意义。Using data of the geochemistry,gas saturation,and rock and mineral compositions of formation water extracted from 34 wells,we discuss the origin of calcium-rich formation water in the 2nd member of the Jurassic Shaximiao Formation(hereafter referred to as the Sha 2 Member)in the central Sichuan Basin,and accordingly explore the implications of the formation water for natural gas migration and accumulation of tight-sand gas reservoirs with sourcereservoir separated.The results indicate that the formation water in the Sha 2 Member exhibits pronounced calcium enrichment and sodium depletion compared to that in other tight-sand gas reservoirs in China.The formation water in the member displays total dissolved solids(TDS)ranging from 3.3 to 45.6 g/L(CaCl_(2) type)and equivalent concentration proportions of Ca^(2+)[γ(Ca^(2+))]ranging from 24.7%to 69.5%,based on which the formation water can be categorized into three types:high-calcium[γ(Ca^(2+))≥60%],medium-calcium[40%≤γ(Ca^(2+))<60%],and low-calcium[γ(Ca^(2+))<40%]formation water.These three types of formation water differ greatly in chemical characteristics and distribution.Specifically,the high-calcium formation water is concentrated in channel sand bodies that are near and connected to Jiao①fault.This type of formation water,among others,exhibits a high average TDS of 34.1 g/L,cations dominated by Ca^(2+),and the lowest Na^(+)/Cl-ratio,desulfurization coefficient,and carbonate equilibrium coefficient.The low-calcium formation water principally occurs in channel sand bodies that are distant from or not directly connected to the Jiao①fault.This type of formation water manifests an average TDS of 3.9 g/L,cations dominated by Na^(+),and the highest Na^(+)/Clratio,desulfurization coefficient,and carbonate equilibrium coefficient.The medium-calcium formation water exhibits an average TDS of 17.7 g/L and slightly different Na^(+)and Ca^(2+)concentrations,with Na^(+)/Cl-ratios,desulfurization coefficients,and carbonate equilibrium coefficients falling between t

关 键 词：水-岩相互作用 源-储分离型气藏 富钙地层水 天然气运聚 沙溪庙组 川中地区 

分 类 号：TE122.1[石油与天然气工程—油气勘探]