Technologies and practice of CO2 flooding and sequestration in China

HU Yongle,HAO Mingqiang,CHEN Guoli,SUN Ruiyan,LI Shi

Table 1 Displacement characteristics of CO2 flooding in low-permeability reservoirs.

CO2 flooding development stage HC pore volume multiple of injected CO2 Dynamic features Phasic adjustment measures Continued water flooding, energy recovery 0-0.05 Formation pressure rises; production continues water flooding characteristics. If water cut is low when turning to gas flooding, fluid and oil production increases substantially, and water cut decreases. If water cut is moderate to high when turning to gas flooding, fluid production increases, oil production doesn’t change much, and water cut increases. Continuous gas injection, optimization of injection rate, and restoring energy by shutting some oil wells. Successive response, increased output 0.05-0.15 Miscible oil wall of CO2 flooding gradually appears in producers; the total water cut begins to decrease, production of liquid and oil gradually increases, and the gas-oil ratio gradually increases. Coordination between plane and profile. Adjust production to ineffective wells. All-round response, stable output 0.15-0.50 Miscible oil wall belt of CO2 flooding appears in all wells; water cut decreases sharply, production of liquid and oil increases to a stable peak period, and the gas-oil ratio increases steadily. Coordination between injection and production. Control fluidity by alternatively injecting water and gas. Overall breakthrough of CO2, high gas-oil ratio >0.50 Overall breakthroughs of CO2 in producers; gas channeling occurs in many producers, with high gas-oil ratio. Fluid and oil production gradually decline. Coordination between injection and production. Control fluidity by alternatively injecting water and CO2; chemical-assisted comprehensive regulation.