摘要
为了明确四川盆地川西坳陷中江气田侏罗系中统沙溪庙组气藏地层水的来源及其所反映的气藏保存条件,对取自该气藏34口气井水样筛选后获得的24个地层水样品,采用多种分析方法,对其化学特征、水型特征、典型化学系数、洛瓦克相图、同位素测试及溯源等进行了系统研究。研究结果表明:①该气藏地层水为CaCl2型,矿化度为6942.0~77289.1 mg/L,pH值平均为6.7,呈现弱酸性,常规离子中,Cl-浓度明显最高。②典型化学系数(变质系数、盐化系数、脱硫系数及阳离子交换系数)特征显示,该气藏地层水处于封闭性较好的还原环境中,有利于天然气的富集和保存。③洛瓦克相图特征显示:取自该气藏不同气井的地层水样其相图特征相似,表明为同一来源;与四川盆地标准剖面所对应的洛瓦克相图对比可知,中江气田沙溪庙组地层水来自三叠系上统须家河组二段—四段。④氢氧同位素和锶同位素分析结果显示,该气藏地层水主要为经过壳源岩改造的古大气降水。结论认为:①该项研究成果有助于深入认识该气藏地层水的化学特征、来源,以及气藏的保存条件、成藏过程,并为相关研究提供理论依据;②所运用的多种方法相结合的技术思路,可以为基于常规水样分析对地层水化学特征开展进一步研究提供借鉴和参考。
In order to identify the provenance of the formation water in the Middle Jurassic Shaximiao Formation gas reservoir of the Zhongjiang gas field,located in the Western Sichuan Depression of the Sichuan Basin,and its implications for gas reservoir preservation conditions,24 samples of formation water screened out from 34 wells were investigated systematically for their chemical characteristics,water types,typical chemical coefficients,Novk phase diagram,isotope testing and provenance by means of multiple analysis methods.The following results are obtained.(i)The formation water is of the CaCl2 type,with the total dissolved solids(TDS)ranging 6942.0-77289.1 mg/L,and an average pH value of 6.7,indicating weak acidity.Among the conventional ions,Cl-is the most abundant.(ii)The characteristics of the typical chemical coefficients(metamorphic coefficient,salification coefficient,desulfurization coefficient,and cation exchange coefficient)suggest that the formation water exists in a well-sealed reducing environment,favorable for gas accumulation and preservation.(iii)The Novk phase diagram characteristics of formation water samples from different wells are very similar,pointing to a common provenance.The comparison with the Novk phase diagram corresponding to the standard section of the Sichuan Basin reveals that the formation water is sourced from the second to fourth members of the Upper Triassic Xujiahe Formation.(iv)The analysis on hydrogen-oxygen and strontium isotopes shows that the formation water is primarily composed of paleometeoric water modified by crust-derived rocks.It is concluded that the research results are helpful for deeply understanding the chemical characteristics and provenance of the formation water,as well as the preservation conditions and accumulation process in this gas reservoir,and provide a theoretical basis for related researches;the technical idea of multi-method combination applied in this study can offer a reference for further researching the chemical characteristics of formation water based on conventional water sample analysis.
作者
高伟
杨松林
黄文元
GAO Wei;YANG Songlin;HUANG Wenyuan(No.3 Gas Production Plant,Sinopec Southwest Oil&Gas Company,Deyang,Sichuan 618199,China;College of Chemistry and Chemical Engineering,Southwest Petroleum University,Chengdu,Sichuan 610500,China)
出处
《天然气勘探与开发》
2025年第5期81-90,共10页
Natural Gas Exploration and Development
基金
中国石化西南油气分公司科技攻关项目“中江气田沙溪庙组气藏气水分布特征及开发对策研究”(编号:KJ-685-2203)。
关键词
四川盆地中江气田
侏罗系中统沙溪庙组
地层水
化学系数
同位素分析
洛瓦克相图
封闭性
气藏保存条件
Zhongjiang gas field of the Sichuan Basin
Middle Jurassic Shaximiao Formation
Formation water
Chemical coefficient
Isotope analysis
Novk phase diagram
Sealing capacity
Gas reservoir preservation condition
