Influence of solvent-to-oil mass ratios on high-pressure asphaltene precipitation

Asphaltene precipitation during solvent-based enhanced oil recovery under reservoir conditions impedes production efficiency and degrades oil quality. This study aims to optimize solvent-to-oil mass ratios to mitigate asphaltene issues and enhance oil upgrading. Experiments using a high-pressure cell simulating reservoir environments were conducted with solvent-to-oil ratios of 3:1, 5:1, 7:1, and 9:1 at temperatures of 120 °C and 250 °C. Increasing the ratio from 3:1 to 7:1 significantly enhanced in-situ asphaltene precipitation, but further increase to 9:1 offered minimal additional benefit, indicating a plateau. Concurrently, the asphaltene content in upgraded oil decreased with higher ratios, stabilizing beyond 7:1. At 250 °C, a substantial reduction in total asphaltene content—averaging a 5.8 wt% decrease-was observed. The discovery of the plateau at 7:1 and the reduced asphaltene precipitation at elevated temperatures provides a novel perspective on balancing solvent use with operational efficiency. These findings contribute to cost-effective and environmentally sustainable practices in enhanced oil recovery operations. These findings identify an optimal solvent-to-oil ratio and temperature under reservoir conditions for maximizing asphaltene precipitation and minimizing asphaltene content in upgraded oil. Optimizing these parameters is crucial for effective asphaltene management and improving the efficiency of solvent-based enhanced oil recovery processes.