塔里木盆地塔北隆起寒武系地层水化学特征、成因及矿物溶解-沉淀模拟

Geochemical features and origin of the Cambrian formation water in Tabei Uplift，Tarim Basin and its mineral dissolution-precipitation simulation

桂亚倩 朱光有 阮壮 曹颖辉 沈臻欢 常秋红 陈郭平 于炳松

Yaqian Gui Guangyou Zhu Zhuang Ruan Yinghui Cao Zhenhuan Shen Qiuhong Chang Guoping Chen Bingsong Yu

通过对塔里木盆地塔北隆起英买-牙哈地区14口井以及轮探1井寒武系地层水的化学成分和离子比例系数的分析，以及水文地球化学模拟，明确了研究区塔北隆起寒武系地层水化学特征和成因与演化。结果表明：塔北隆起寒武系地层水是以Na+K和Cl为主的高矿化度CaCl型地层水。地层水中Na+K和Cl浓度与矿化度的相关性好，Na+K，Ca，Mg，Cl和SO浓度随埋深的增加呈先减小后增大的趋势，与矿化度随埋深的变化趋势一致，由此将地层水划分为越流泄水浓缩带和深部渗滤浓缩带。钠氯系数为0.39～0.55，平均值为0.51；脱硫酸系数为0.07～1.91，平均值为0.35。Phreeqc软件模拟矿物饱和指数得出：白云石的饱和指数为-3.43～1.95，平均值为-0.10，50.91 %的白云石沉淀；石膏的饱和指数为-1.77～0.12，平均值为-0.80，94.64 %的石膏溶解；方解石的饱和指数为-0.88～1.62，平均值为0.55，18.18 %的方解石溶解。研究区塔北隆起方解石的白云石化和石膏溶解导致现今地层水中Ca富集，Mg亏损。塔北隆起寒武系地层水变质程度小，是由海水经历蒸发浓缩、离子吸附和水-岩相互作用演变形成的。

The chemical compositions and ion ratio coefficient of the Cambrian formation water taken from 14 wells in Yingmai and Yaha areas and Well Luntan 1 in the Tabei Uplift， Tarim Basin， are analyzed and applied to carry out hydrogeochemical simulation， with the geochemical characteristics， origin and evolution of formation water therein clarified. The results show that the Cambrian formation water in the study area is of CaCl type， high in total dissolved solids （）， and dominated by Na+K and Cl. The concentration of Na+K and Cl is well correlated with of the formation water. Concentration of ions like Na+K， Ca， Mg， Cl and SO tends to decrease first and then increase with the increase of burial depth， consistent with the trend of change with burial depth. Vertically， two hydrochemical zones can be identified in the study area： an overflow-discharge concentration zone and a deep percolation concentration zone. Its sodium-chloride coefficient ranges from 0.39 to 0.55， averaging 0.51； de-sulfuric acid coefficient varies from 0.07 to 1.91 with an average value of 0.35. The results of mineral saturation index simulation by Phreeqc software suggest that saturation index of dolomite ranges from -3.43 to 1.95 with an average of -0.10， and 50.91 % of the dolomite is precipitated； the saturation index of gypsum ranges from -1.77 to 0.12 with an average of -0.80， and 94.64 % of the gypsum is dissolved； the saturation index of calcite ranges from -0.88 to 1.62 with an average of 0.55， and 18.18 % of the calcite is dissolved. A combination of calcite dolomitization and gypsum dissolution in the study area leads to enrichment of Ca and deficit of Mg in the current formation water. The Cambrian formation water low in metamorphic degree in the study area， can be attributed to seawater evaporation and concentration， ion adsorption and water-rock interactions.

10.11743/ogg20220116