Study on optimization and mechanism of CO2 injection to enhance oil recovery in mid-deep heavy oil reservoirs

Abstract

In order to improve the oil recovery of mid-deep heavy oil reservoirs, this study investigates the efficiency of enhanced oil recovery and the mechanisms of oil displacement in mid-deep heavy oil reservoirs using different injected gases (N2, CH4, CO2) and development approaches (gas flooding and gas huff-n-puff) through a series of experiments. These experiments include high-pressure physical properties tests of crude oil after gas injection, displacement efficiency tests of gas injection, and displacement efficiency tests of gas huff-n-puff. The results indicate that for mid-deep heavy oil reservoirs, the preferred optimal injection gas is CO2, with gas huff-n-puff being the most effective development method. Furthermore, a numerical simulation study was conducted to explore the adaptability parameters of CO2 huff-n-puff development in different well patterns, encompassing variables such as the amount of gas injected per cycle, crude oil viscosity, reservoir permeability, and oil layer thickness.

Evaluation of Potential of CO2-Enhanced Oil Recovery (EOR) and Assessment of Capacity for Geological Storage in a Mature Oil Reservoir within Upper Assam Basin, India

“…As the CO 2 injection rate is increased, more CO 2 is introduced into the reservoir, increasing the degree of mixing between CO 2 and oil. This thorough mixing enhances the displacement of oil from the reservoir pores, leading to increased recovery. , Also, at higher injection rates, more CO 2 is available to dilute the oil, resulting in greater viscosity/density reduction and oil swelling, leading to enhancement in the mobility of oil . The increase in recovery as a function of increasing CO 2 rate is also attributable to the fact that it can penetrate deeper into the reservoir, contacting more oil-bearing zones, and displacing oil effectively toward the producers.…”

Experimental Study on Oil–Gas Interaction Mechanism during Offshore Heavy Oil Gas Injection

“…However, there is currently limited research on the compositional changes in heavy oil after the injection of hydrocarbons, , as well as the comparison of miscibility pressures. − Moreover, the density, viscosity, and composition of heavy oil are significantly influenced by gas injection, which in turn affects displacement efficiency. − To address these issues, this study investigates the effects of CO 2 , natural gas, and nitrogen injection on the heavy oil viscosity, density, expansion ratio, and compositional changes through indoor experiments. It explores the minimum miscibility pressures and displacement effects of different gases, aiming to provide insights for the selection of gas injection methods in heavy oil fields and improve the mechanisms of gas injection for enhanced heavy oil recovery. …”