Laboratory study of CO2 channeling characteristics in ultra-low-permeability oil reservoirs
WEI Qi1,2,3, HOU Jirui1,2,3, HAO Hongda1,2,3, SONG Zhaojie1,2,3
1 Enhanced Oil Recovery Institute, China University of Petroleum-Beijing, Beijing102249, China 2 Basic Theory Laboratory of Enhanced Oil Recovery in Low Permeability Oilfields, Key Laboratory of Tertiary Oil Recovery, PetroChina, Beijing 102249, China 3 The Ministry of Education Key Laboratory of Petroleum Engineering, Beijing 102249, China.
The production and gas channeling characteristics of CO2 flooding in ultra-low-permeability reservoirs was examined in detail through laboratory experiments under formation pressure and temperature. The factors influencing injection pressure and reservoir heterogeneity with CO2 channeling characteristics were also systematically studied. The results showed that the
CO2 flooding process in ultra-low-permeability reservoirs can be divided into three stages: (1) a gas-free stage, (2) a gas breakthrough stage and (3) a gas channeling stage. Among them, the oil recovery of the gas breakthrough stage contributed greatly to the total recovery, which is the key stage for improving oil recovery in ultra-low-permeability layers. The injection pressure of CO2 and the reservoir heterogeneity can affect the development of the gas-free stage, gas breakthrough stage and gas channeling stage to different degrees. Thus, maintaining the formation pressure, improving the heterogeneity of the reservoir and inhibiting the gas channeling to prolong the gas breakthrough stage during CO2 flooding are effective ways to improve the development efficiency of CO2 flooding in ultra-low-permeability layers.
Key words：
ultra-low-permeability reservoir; CO2 flooding; injection pressure; heterogeneity; gas channeling
WEI Qi, HOU Jirui, HAO Hongda, SONG Zhaojie. Laboratory study of CO2 channeling characteristics in ultra-low-permeability oil reservoirs. Petroleum Science Bulletin, 2019, 02: 145-153.
