Volume 59

Dynamic characteristics and influencing factors of CO2 displacement in tight oil reservoirs assisted by direct current electric field Wenting Guo, Zhengfu Ning

Abstract

Experiments on CO2 displacement were conducted using cylindrical rock cores under various voltages, electric field modification times, and different injection-production parameters. The dynamic characteristics and contributing factors of direct current (DC) electric field-assisted CO2 displacement on enhanced oil recovery were analyzed. The study shows that DC electric field-assisted CO2 displacement development can be divided into four phases: high-speed oil and gas production induced by DC electric fields, oil-carrying gas production, DC electric-assisted dissolved gas drive, and low-speed oil production. Voltage and electric field modification time are the primary factors affecting the effectiveness of DC electric field-assisted CO2 displacement development, followed by the CO2 injection volume and extraction speed, with the CO2 injection rate having the least impact. An optimal voltage exists that maximizes recovery efficiency; the longer the electric field modification time, the higher the recovery rate, although the rate of increase gradually slows. High volumes of CO2 injection and slow extraction can enhance recovery rates. The stability of bottom-hole pressure in injection-production wells can serve as an indicator of the completion of electric field modification. The main contributors to the recovery rate in DC electric field-assisted CO2 displacement development are the effects of the DC electric field on CO2 dissolution and electroosmosis, followed by diffusion and CO2 flow propagation.

Keywords tight oil, DC electric field, CO2 flooding, dynamic characteristics, oil displacement mechanism