Abstract: The formation water contains much higher concentration of solids and total solid concentration ranges from 100g/L to more than 300g/L in the Ordovician,Carboniferous and Triassic reservoirs at Tahe oil field and adjacents,which was considered as forming in a closed hydrogeological environment and disconnected with each other. The new concludes are made by the analysis of the formation water:a)the chemical profiles of formation water are inversion in the Ordovician,Carboniferous and Triassic reservoirs,the higher total solids concentration is formed by solution of salts in the sediment rocks of the area;b)the δD and δ¹⁸O are lighter and maybe composed of surface water and formation water;c)the formation of oil field water is the result of surface water leaching the NaCl containing in the sediments of the area. All these indicate that the hydrogeological environment is not colsed,but opening in the area. The influence of the opening environment in the migration and accumulation of oil and gas must be taken into consideration in the exploration of Tahe oil field and adjacents.