Impact of gas property on gas drive in extremely low permeability oil reservoir—A case study of Block Fang48 in Daqing Oilfield

Block Fang48 in Daqing Oilfield is an extremely low permeability oil reservoir. Physical modeling of long core displacement has been performed by using displacing media such as water, CO2, N2 and natural gas to determine the impact of gas type on development response of such reservoirs. The result shows that, Block Fang48 has low water injection capacity, water breaks through in an early time, and water-cut rises rapidly. In gas drive, under the same condition, CO2 and natural gas drives have higher recovery factor, oil draining rate and gas injection capacity than N2 drive, while with producing gas-oil ratio lower than that of N2 drive. Therefore, the optimal method of gas drive for developing Fang48 is CO2 flooding; the next is natural gas drive. As CO2 is corrosive to equipments, anti-corrosive measures shall be considered when selecting CO2 flooding.