Experimental investigation of carbon dioxide flooding in heavy oil reservoirs for enhanced oil recovery

With the attention paid to greenhouse gas emission reduction all over the world, CO2 capture, utilization and storage technology has developed rapidly. Predecessors have done a lot of work on the effect of CO2 on properties of the oil, the changes of parameters after CO2 injection are different. Through PVT, slim tube test and phase state simulation, this work studied the influence law of CO2 injection on the properties of heavy oil in offshore reservoirs in eastern China. It defines the adaptability and oil displacement mechanism of CO2 flooding in the reservoirs. In this work, 12 oil displacement experiments were carried out to quantify the effect of injection sequence, slug size, gas injection rate, and soaking time on oil recovery in the hydrogen carbon reservoir. These experimental results have indicated the influence of different factors on oil displacement effect. It provides strong evidence for the efficient development and enhanced oil recovery of the oilfield. The results indicate that the gas-water alternative injection is better than continuous water flooding or continuous CO2 flooding by improving the ultimate recovery at 8.9% and 12.7% respectively. A larger CO2 slug is beneficial to improve the ultimate oil recovery and the injection rate of CO2 slightly affects the ultimate oil recovery factor. Longer soaking time can improve the ultimate recovery either. The ultimate recovery increases rapidly with the soaking time when it less than 24 h, but the ultimate oil recovery hardly increases when the soaking time is longer than 24 h. (C) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).