From the viewpoint of geological development, the mechanisms of formation of oil-field waters in non-marine basins and their relation with oil-gas reservoirs are discussed briefly. Sedimentary basins differing in geological setting and physical geographical environment would lead to a diverse evolution of fossil lake basin water body in chemical composition in the process of formation, development and extinction by themselves, resulting in oil-field waters with complex; variable and characteristic compositious China's non-marine basins are mostly derived from fossil lake basins. The substantial petroleum-generating stage is highly expected during the development of these fossil lake basins. The production of hydrocarbons responsible for petroleum is always accompanied by the production of sedimentary water. As a result, oil-gas migration took place under the action of high-pressure water and led to the preferential accumulation in the surrounding geological structures as a girdle pattern. In the oil-gas-bearing basins where seeping water is abundant, oil-gas reservoir are found distributed mainly along the “intersection zone” -- the “erestal plane”between the “ fossil-dewatering” of sedimentary water and the “fossil-interpolation”of seeping water. Due to the influence of various factors and the geochemical reactions, oilfield waters in Chiua's non-marine basins have remarkable “ion differential” phenomenon. Based on the phenomenon four types of ion assemblages can be distinguished.
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