柴达木盆地北缘冷湖四号构造油田水水化学组成及其分布特征

Hydrochemical Components and Their Distribution Characteristics of Oilfield Waters in No. 4 Structure of Lenghu,Qaidam Basin

柴达木盆地北缘冷湖地区赋存大量深部油田水。分析结果显示,冷湖四号构造地区的油田水为CaCl_2型,具有较高Ca含量,一些成分还具有比较明显的区域分异特征。相比柴达木盆地西部,柴北缘油田水的矿化度、K、B、Li等明显偏低。油田水水化学特征系数指示了研究区地层具有良好的封闭性,主要化学组分的富集作用与浓缩作用密切相关。推测碳酸盐、硅酸盐在长期水—岩作用下的溶解对油田水主要化学成分有重要贡献,而区域断裂的发育导致少量样品中的高F含量。

Plenty of oilfield waters were found in Lenghu area on the north edge of Qaidam Basin. Analytical results show that the oilfield waters can be assigned to CaCl_2 type water and are charaterized by high content of Ca. Some contituents obviously have the regionally differentiated charateristics. Whereas,compared to components of oilfield water in western Qaidam Basin,these waters in north basin have lower values in TDS and some components such as K,B,Li and so on. Hydrochemical charateristic coefficients of oilfield waters indicate that the strata in study area closed well and the richment of main components were closely correlated to concentration of water. It is deduced that during long-term water-rock reaction,the solution of carbonates and silicates has a siginificant contribution to main components of oilfield water.While the developed faulds cause high contents of F in a few samples.