Abstract:

There are two kinds of oil field water(CaCl₂ and NaHCO₃) in Yanqi basin, the water mineralization is 5.5～73.2/1,presenting in forward water chemical section character with apparent zoning. CaCl₂ type is mainly distributed in northern area of Baobei block,in Baolang Sumu structural belt, whereas NaHCO₃ is chiefly distributed in the blocks of Baonan,Benbutu,Zhongmachang as well as some areas of Baozhong block. Organic mater abundance in oil field water is lower(below 2×10^-6) while organic acid content is very high(2546×10^-6～5148×10^-6 and acid content is usually 0.12×10^-6～4.63×10^-6. Therefore, it is confirmed that there are three hydro-geologic belts in the basin namely; free alternative belt, slow alternative belt and hindered belt, and the preserving condition in the north is better than that in the south and central part is better than that in the edge of the basin.

Key words: oil field water, geochemistry, oil-gas pool, zoning, Yanqi basin