Conformance control study of preformed particle gels (PPGs) in mature waterflooded reservoirs: numerical and experimental investigations

Abstract

Improving conformance control in reservoirs with a heterogeneous permeability distribution is the objective of many enhanced oil recovery (EOR) methods. In recent years, the injection of preformed Particle Gels (PPGs) is suggested as an effective EOR method to control the in-depth conformance of waterfronts. In this study, a new mathematical transport model of PPG injection in mature waterflooded reservoirs is developed. The model is based on the experimental results of PPG swelling ratio and entrapment analyses in a carbonate rock sample. The entrapment is considered as a function of the PPG-to-pore size ratio, fluid velocity, temperature, salinity, PPG concentration, and swelling ratio. The formulations of the resistance factor (RF) and residual resistance factor (RRF) are obtained from the injection experiment results at various fluid velocity and PPG concentrations. The entrapment model is coupled with the transport equations of the MATLAB Reservoir Simulation Toolbox (MRST). The model is validated by predicting the pressure drop changes during the 1D PPG injection experiments at three different flow rates. The validated model is then used to predict PPG transport behavior in several 3D field-scale scenarios. The sensitivity analysis results show that a higher recovery increment can be achieved when the reservoir permeability contrast is increased. There is an appropriate PPG-to-pore size ratio (i.e., DPT of 1.75) that can guarantee deep conformance control and avoid PPG washing out during post-waterflooding. Furthermore, the PPG concentration of 1750 ppm resulted in a significant entrapment in the porous medium.