鄂尔多斯盆地彭阳地区侏罗系延安组地层水化学特征及成因类型分析

运用地层水物理化学分析方法对鄂尔多斯盆地彭阳地区侏罗系延安组地层水离子浓度、矿化度、离子组合等特征进行综合研究，从而揭示其类型、演化过程和成因。研究结果表明，研究区地层水以Cl^–、（ Na⁺+ K⁺）离子为主，SO₄^2-及Ca²⁺离子次之，具较高矿化度；地层水为盐水和卤水，主要为CaCl₂型和Na₂SO₄型；Piper三线图解表明，未发生淡水混入作用，整体为交替停滞的缺氧还原环境。研究区延安组地层水矿化度高、离子浓度组合特征反映地层具较强的还原环境，有利于油藏保存；为原生沉积水，在演化过程中受到了蒸发浓缩作用、水—岩作用及生物作用的共同影响；地层水分布受前侏罗纪古地貌的影响较强，不同古地貌单元地层水的化学性质明显不同。

Analysis of the hydrochemical characteristics and genesis of the Jurassic reservoir in the Pengyang area of Ordos Basin,NW China

By using the method of physical and chemical analysis of formation water, the ratio of ion concentration, formation water salinity and the hydrochemical characteristics of the Jurassic Yan′an Formation in Pengyang area, Ordos Basin were studied, and the types, evolution and origin of formation water were revealed. The results show that the formation water mainly composed of Cl^- and （Na⁺, K⁺） ions, followed by SO₄^2- and Ca²⁺ ions, with high salinity. The formation water is saline and brine. According to Surin′s classification, the main types are CaCl₂ and Na₂SO₄. Piper′s three-line diagrams show that there is no freshwater mixing and the whole environment is hypoxic reduction with alternate stagnation. The combination characteristics of high salinity and ion concentration of formation water in Yan′an Formation in the study area reflect that the formation has a strong reduction environment, which is conducive to reservoir preservation. The origin of formation water should be primary sedimentary water, which is affected by evaporation and concentration, water-rock interaction and biological action, and the distribution characteristics are strongly influenced by pre-Jurassic palaeogeomorphology, and the hydrochemical properties of different palaeogeomorphological units are obviously different.