塔里木盆地油田水文地球化学

THE HYDROGEOCHEMISTRY OF OIL-FIELDS IN TARIM BASIN

塔里木盆地油田水总矿化度６０ｇ／Ｌ－３２０ｇ／Ｌ，与氯离子浓度呈正相关，总体上受铝硅酸盐矿物成岩改造影响甚小。油田水主要为部分贫镁型和完全耗镁型两种。部分贫镁水型（镁的摩尔数多占Ｎａ＋Ｃａ＋Ｍｇ的１％－２％，钙可高达１５％－２２％）被认为来自方解石的白云石化作用和斜长石的溶解作用；氧同位素值、Ｌｉ、Ｂ和Ａｌ浓度随埋深而增大，高的锶浓度指示了水－铝硅酸盐矿物反应是受温度控制的，Ｍｇ－Ｌｉ可指示古地温。氢氧同位素演化可为同步增大，还可为氧同位素明显变重而氢同位素正偏移小。中新生界溴浓度较低、古生界较高，溴浓度受海陆相沉积环境和蒸发浓缩作用的控制。

The Concentrations of total dissolved solids (TDS) range between 609/L and 320g/L,and have a positive correlation with Cl contents, that suggests that TDS are slightly affeted by aluminosilicate diagenetic alteration. Water is mainly subdivided into partially Mg-depleted and fully Mg-depleted water types. The former type(Mg is 1 to 2 mol% and Ca may range from 15 to 22 mol% of the sum of Na, Ca and Mg) is explained to be formed by dolomitization of calcite and plagioclase dissolution. δ18O and the concentrations of Li, B, Al increase with the burial depth. Sr-content which is relatively higher than the average indicates that reactions between water and aluminosilicate are controlled by the temperature. Hence, the temperature can be calculated with Mg-Li relationship. δD and δ18O isotopic compositions may synchronously increase in evolutional pathway or δ18O has a large positive shift whereas δD has a small shift. The concentrations of Br are lower in Cenozoic and Mesozoic sections than those in Paleozoic section that suggests that the sedimentary environment and evapo-concentration have an important effect to the content of Br.