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

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CaCl2型地层水.地层水中Na++K+和Cl-浓度与矿化度的相关性好,...

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

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 CaCl₂ type， high in total dissolved solids （TDS）， and dominated by Na⁺+K⁺ and Cl^-. The concentration of Na⁺+K⁺ and Cl^- is well correlated with TDS of the formation water. Concentration of ions like Na⁺+K⁺， Ca²⁺， Mg²⁺， Cl^- and SO₄^2- tends to decrease first and then increase with the increase of burial depth， consistent with the trend of TDS 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 Ca²⁺ and deficit of Mg²⁺ 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.