Growing global energy demand and the limitations of renewable sources make unconventional fossil fuels such as heavy oil more attractive to meet future energy needs. Heavy oil, which comprises a significant portion of global oil reserves, poses unique recovery challenges due to its high viscosity and density. Among various enhanced oil recovery techniques, thermal methods such as hot-water flooding have proven effective and economically viable. This technique reduces oil viscosity, improving mobility and sweep efficiency in the reservoir. While previous studies have explored hot-water flooding in high-permeability cores and under isothermal conditions, researchers Md Irshad Ansari and Suresh Kumar Govindarajan investigate the complexities introduced by heterogeneous reservoirs, especially those with dispersed clay in sandstone formations, which alters permeability and fluid flow behavior.
Their study "Hot-Water Flooding Performance Assessment in Heterogeneous Reservoirs through Numerical Simulation" addresses this research gap by modeling a heterogeneous sandstone reservoir with spatially distributed clay to simulate realistic subsurface conditions. Using vertical wells and nonisothermal conditions, the research evaluates the feasibility and performance of hot-water flooding in recovering heavy oil. It investigates how reservoir heterogeneity and injection velocities influence production, while also analyzing the sensitivity of key parameters such as initial oil saturation, pore size distribution index, and reservoir temperature. The findings highlight the critical role of spatial permeability variations and thermal dynamics in optimizing oil recovery, offering valuable insights for civil engineers and energy professionals involved in subsurface resource development and EOR strategy design. Learn more about their research in the Journal of Energy Engineering at https://ascelibrary.org/doi/10.1061/JLEED9.EYENG-6091. The abstract is below.
Abstract
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.
Learn more about the researchers’ extraction findings and their potential in the ASCE Library: https://ascelibrary.org/doi/10.1061/JLEED9.EYENG-6091.
