川西坳陷新场气田须二气藏地层水成因研究——水化学和锶同位素证据  

Hydrochemistry and Sr isotope constraints on the genesis of formation water in the 2nd member of Xujiahe Formation gas reservoir in Xinchang gas field, Western Sichuan Depression

作　　者：山俊杰 毕有益[1] 邓美洲[1] 严焕榕[1] 周小荣 郑艳 SHAN Jun-je;BI You-yi;DENG Mei-zhou;YAN Huan-rong;ZHOU Xiao-rong;ZHENG Yan(Research Institute of Exploration and Development,Southwest Oil&Gas Company,SINOPEC,Chengdu 610041,China;Post-Doctoral Scientific Research Station,Southwest Oil&Gas Company,SINOPEC,Chengdu 610041,China;Geology Experiment Center,Southwest Oil&Gas Company,SINOPEC,Chengdu 610081,China)

机构地区：[1]中国石化西南油气分公司勘探开发研究院,四川成都610041 [2]中国石化西南油气分公司博士后工作站,四川成都610041 [3]中国石化西南油气分公司地质中心实验室,四川成都610081

出　　处：《岩石矿物学杂志》2023年第5期735-744,共10页Acta Petrologica et Mineralogica

基　　金：中国石化科技部项目(P21040)。

摘　　要：地层水是影响气田产能开发的重要因素之一,气井遇水会降低储层气相渗透率,从而导致气产量迅速下降,严重制约单井产能的提高。目前已有的研究对须二气藏地层水的物质来源认识仍然存在一定争议。本文从主微量元素、水岩相互作用以及锶同位素组成特征方面对川西坳陷新场气田须二气藏11口生产井的地层水进行了系统研究,结果显示须二气藏地层水具有低矿化度(55 166.00~122 547.41 mg/L)、高Br-和Sr^(2+)含量(分别为642.00~1 711.00 mg/L和670.00~1 780.00 mg/L)及^(86)Sr/^(87)Sr值(0.715 27~0.721 77)的特征,表明研究区地层水Sr同位素来源区别于海相碳酸盐岩,更符合砂岩风化特征。地层水中Ca的富集主要与砂岩储层成岩自生矿物的溶解有关,在深部水岩相互作用下,Sr以类质同象的方式代替Ca并且获得了有机质中的Br,同时使得Br更加富集。以上研究结果为今后该气藏赋水层位的预测提供了理论依据。Formation water is one of the significant factors affecting the development of gas fields.The presence of water in gas wells can decrease the gas phase permeability of the reservoir,leading to a rapid decline in gas production and severely restricting the improvement of well productivity.Furthermore,there is still some controversy regarding the sources of formation water in study area.In this study,through an investigation of the formation water system in 11 production wells in the Xinchang gas field,hydrochemical and strontium isotopic analyses were conducted to examine the major and trace elements,water-rock interactions,and strontium isotope characteristics.The results indicate that the formation water in the 2nd member of the Xujiahe Formation gas reservoirs exhibits characteristics of low total dissolved solids(ranging from 55166.00 to 122547.41 mg/L),high bromine(Br)and strontium(Sr)contents(ranging from 642.00 to 1711.00 mg/L and 670.00 to 1780.00 mg/L,respectively),and ^(87)Sr/^(86)Sr ratios(ranging from 0.71527 to 0.72177).These characteristics suggest that the source of strontium isotope in the formation water is different from that of marine carbonate rocks and is more consistent with sandstone weathering.The enrichment of calcium(Ca)in the formation water is primarily related to the dissolution of authigenic minerals in the sandstone reservoir.During deep water-rock interactions,strontium replaces calcium in a cation-exchange manner and acquires bromine from organic matter,leading to an enrichment of bromine.These findings provide a theoretical basis for predicting the water-bearing horizons of the reservoir in the future.

关 键 词：川西坳陷 须二气藏地层水 水化学 锶同位素 

分 类 号：P618.13[天文地球—矿床学] P641.5[天文地球—地质学] P597