Greening strategy for heavy oil thermal recovery assisted by environmental-friendly solvent dimethyl ether

Abstract

The heavy oil recovery process, traditionally fueled by steam derived from burning fossil fuels, is a considerable source of carbon emissions, contributing to the accentuation of environmental concerns. The integration of dimethyl ether (DME) into this process emerges as an innovative and eco-conscious strategy. This study investigates the mechanisms by which DME enhances steam flooding efficiency through the construction of a microscopic visualization model to examine DME-assisted steam flooding. Eleven controlled experiments with varied fluid types, injection modes, and temperatures reveal complex EOR mechanisms. Sandpack flooding experiments, comparing different DME injection rates with pure steam flooding, offer insights into production characteristics. The results show diverse forms of remaining oil in pore spaces—points, strips, clusters, and films. Comparative analysis indicates that DME flooding outperforms hot-water flooding and nitrogen flooding. The coinjection method is more effective than slug injection. High-temperature fluids yield better results. The optimal injection method is DME–steam coinjection flooding at 150 °C. DME addition reduces the heavy oil viscosity by 57.99 %, lowers the injection-production pressure differential from 4.9 MPa to 2.3 MPa, and advances the oil production breakthrough. Additionally, the peak oil production rate is improved by 0.75 mL/min. These effects contribute to a 21.74 % increase in the final oil recovery factor. The strategic integration of DME aligns with global sustainability goals, by mitigating environmental impacts through reduced emissions and improved energy efficiency while maintaining economic viability of heavy oil recovery operations.