THE HYDROCHEMICAL CHARACTERISTICS OF NON-MARINE OIL-FIELD WATER IN CHINA AND ITS EVOLUTION PATH

Basing on a large number of analytical data, the hydrochemical characteristics of non-marine oil-field water in China and its evolution path are discussed. Along with the generation and development of sedimentary basin, the non-marine oil-field paleowater underwent a series of complicated processes of hydrogeochemical evolution, and eventually transformed into the present status. The hydrochemical composition changed along a main trend with increasing concentrations of anion Cl^- and cation Na⁺. The differences among hydrochemical types depend on the concentrations of secondary ions and the degree of mineralizationi meanwhile, the degree of mineralization and the hydrochemical type show distinct zonation from north to south, reflecting the influences of paleoclimatology and paleohydrochemistry. In addition, the formation, occurrence, and circulation of oil-field water, and the evolution of hydrochemistry accorded with the formation, migration and accumulation of oil and gas. All these were strictly controlled by the second-ordered tectonic elements-sedimentary depressions-within the petroliferous basins and thus appeared as a single complex during hydrochemical evolution. This is an important characteristic of non-marine oil-field water.