Hot-Water Flooding Performance Assessment in Heterogeneous Reservoirs through Numerical Simulation

The heterogeneity of reservoirs is a vital factor that influences the performance of hot-water flooding. The random spatial distribution of clay in the sandstone layer reduces the size of the pore throat and subsequently reduces the permeability drastically, which impacts the hot-water flooding performance. Hot-water flooding performance evaluation using numerical simulation at large scale becomes highly necessary in such a heterogeneous environment prior to the field scale application. The present study proposes an improved numerical model by coupling energy transfer and multiphase flow under the evolution of rock and fluid properties to capture oil production behavior more realistically. The impact of the range of heterogeneity and injection velocity are evaluated on the hot-water flooding performance. Sensitivity studies were also performed to analyze the impact of the pore size distribution index, initial oil saturation, and initial reservoir temperature on the performance of hot-water flooding. The heterogeneity in permeability variation impacts the cumulative oil production. The cumulative oil produced is observed to be 301.01 m3 at mean permeability of 110.125 mD with standard deviation 14.35 mD, which is 0.05%, 0.27%, and 0.64% higher in comparison to the reservoir possessing mean permeability of 110.125 mD with standard deviation of 18.18, 27.36, and 41.22 mD, respectively. The oil production declines at higher heterogeneity owing to presence of larger nonuniformity in the reservoir’s permeability, which gives rise to uneven convective heat transport in the formation and makes the hot water pass through the layers possessing sandstone of larger permeability rapidly. The increase in injection velocity enhances the convection effect and subsequently temperature propagation, which reduces the viscosity of the oil up to longer distance. The cumulative oil produced is observed 328.35 m3 at 2×10−6 m/s, which is 9.08% and 12.26% larger in compared to 1×10−6 and 8×10−7 m/s, respectively. The pore size distribution index impacts hot-water flooding by increasing the oil’s relative permeability. The reservoir possessing a lower magnitude of the pore size distribution index produces larger cumulative oil production than the larger pore size distribution index. The reservoir possesses high initial oil saturation, and large initial reservoir temperature leads to better oil production. Hot-water flooding effectively improves cumulative oil production from reservoirs possessing the least permeability deviation at a higher injection rate. The reservoir with a lower pore size distribution index, higher initial oil saturation, and larger initial reservoir temperature significantly assists hot-water flooding performance in a heterogeneous environment. The present study can serve as a reference for the further study of hot-water flooding in heterogeneous sandstone reservoirs possessing dispersed clay.