摘要
Based on the analysis of Shahejie Formation water in Huimin Sag,the geochemical characteristics and origin of formation water were analyzed.The results show that these waters are of CaCl2 type with main chemical composition of anion Cl-and cation(Na++ K+).Vertically,the chemical composition of these waters alternately increased and decreased.The water chemistry parameters reflect the Member 2 and Member 4,the middle and lower Member 3 of Shahejie Formation have good sealing.The formation water was saturated by CaCO3,but not yet saturated by CaSO4.The degree of ions’ enrichment and deletion can be presented by using of the composition contrasting with the seawater and lacustrine saline-water evaporation trajectory.Thereby,the origin of formation water was analyzed based on ions’ enrichment and deletion,and the result indicates the appearance of concentration of Cl-and Na+,enrichment of Ca2+,deletion of Mg2+ and SO42- are owing to the combine effects of evaporation,dolomitization,desulfitation and hydrocarbon generation.Moreover,the lower-salinity areas in which each formation above the Member 4 of Shahejie Formation has lower-salinity water all occur in Linnan sag,and the clay mineral dehydration in Linnan sag can be used to interpret this phenomenon in the plane.