Numerical Modeling of Waterflooding Experiments in Artificially Fractured and Gel Treated Core Plugs by Embedded Discrete Fracture Model of a Reservoir Simulation Toolbox

Abstract

The fluid flow dynamics of the matrix and fractures are significantly different from each other. Fractures are high-permeability flow channels that serve as the main flow units. On the other hand, the Matrix takes up the majority of the reservoir volume and is generally regarded as the main storage unit. The primary goal of this research is to investigate numerically the effects of fractures and polymer gel treatment on oil recovery during waterflooding of artificially fractured core plugs. In this study, the MATLAB Reservoir Simulation Toolbox (MRST) was used for the numerical solution. Different numerical models were developed using MRST to describe three main cases: non-fractured core plug, fractured core plug, and polymer gel treated core plug. Following the creation of the physical models, 2 PV water was introduced into all core plugs. Oil recovery and water saturation profiles vs. time plots were obtained. The standard Buckley-Leveret solution is utilized to evaluate the numerical model, and the fractures are modeled using the Embedded Discrete Fracture Model (EDFM). The results of the simulations were compared with the results of the experiments. In the experiments, results were recorded after 2 PV water injections. For the polymer gel treated core plugs, 2 PV more water was injected after the polymer gel operation. same injection volumes as used in the MRST model. For an artificially fractured core sample, initial oil recovery was measured as 28.57% experimentally and 28.87% with MRST. Then polymer gel was applied to the core plug, increasing the oil recovery to 42.85% experimentally and to 40.83% with MRST. Similarly, before and after polymer gel operation, mean water saturation was measured as 58.34% and 66.5%, respectively. MRST results showed mean water saturation of 58.38% and 65.45%. It is clear from both numerical and experimental models that the existence of fractures decreases the overall hydrocarbon recovery. Polymer gel treatment decreases fracture permeability, resulting in a more uniform sweep and increased overall recovery. Additional oil recovery was observed after polymer gel treatment. Besides, polymer gel treatment of the matrix is also efficient for increasing the recovery and leads to the same results. Moreover, the effects of the fracture aperture and fracture permeability on the recovery were also investigated. Fracture aperture directly impacts the recovery of the low aperture values when the permeability is constant. Similarly, permeability directly affects recovery for high values when the aperture is constant. Finally, the results showed that experimental and numerical findings are significantly close to each other for all non-fractured, fractured, and polymer gel-treated cases.