Evaluation of Viscosity Reducers for Heavy Oil Reservoirs: Experimental Testing and Numerical Simulation.

The application of thermal recovery methods in Chad's heavy oil fields has proven to be challenging, necessitating the development of chemical cold production technologies. The mechanisms causing heavy oil viscosity remain unclear, and the effects of adding viscosity reducers in wells with varying water contents are not well understood. In this study, the composition and structure of Chad's heavy oil samples were experimentally analyzed, revealing that the viscosity is primarily due to the accumulation of isoprenoid-like components and the high concentration of side-chain naphthenes in the oil's saturated fraction. Based on this mechanism, viscosity reducers were screened, with DG, a high-molecular-weight water-soluble viscosity reducer, demonstrating the most effective results. Numerical simulation was then employed to characterize the mechanism of viscosity reducers and to model the impact of adjusting daily production rates and introducing viscosity reducers in wells with different water contents on the cumulative oil recovery. The field numerical model was used to simulate for 10 years, and the results showed that for high water content wells, the injection of viscosity reducer reduced the daily fluid volume by 10%, and the cumulative recovery rate increased by 6.75%; for low water content wells, the injection of viscosity reducer increased the daily fluid volume by 20%, and the cumulative recovery rate increased by 3.08%. This research aims to provide new insights into the development of heavy oil reservoirs.