Long Core Simulation of Advanced CO2 Injection in Ultra-Low Permeability Reservoir

CO₂ flooding is a promising enhanced oil recovery method both on technical and environmental bases, especially for ultra-low permeability reservoir, because this reservoir is characterized by low porosity, ultra-low permeability, low deliverability, water sensitive, and water-flooding inefficient. In this paper, crude oil and cores from H-59 block of Jilin oilfield were used to conduct tests for studying oil recovery of different types of gas injection. Continuous CO₂ steam injection and advanced CO₂ steam injection were compared to select the optimal injection patterns. Results indicate that oil recovery of advanced CO₂ steam injection is higher than continuous CO₂ steam injection. It is considered that injecting CO₂ steam before production can keep the pressure of the ultra-low permeability reservoir effectively, and the advanced injected CO₂ can highly contact with crude oil, which will decrease the viscosity and swell the volume of the oil, ultimately improve mobility of the oil.