Low Molecular Weight Sodium Polyacrylate to Minimize Polymer Retention in Clayey Formations

Abstract

Abstract Clay particles can irreversibly adsorb polymers, limiting the availability of flowing polymers to sweep the reservoir. The adsorption in the near wellbore region can also lead to reduced injectivity. This study investigates the potential of sacrificial agents, specifically sodium polyacrylate, to mitigate polymer retention during polymer flooding. This research aims to determine whether the low molecular weight sodium polyacrylate can minimize polymer retention and enhance the performance of polymer floods in low permeability reservoirs. Comprehensive experiments were conducted to evaluate the effectiveness of the sacrificial agents. Rheological measurements assessed any potential alteration in the main polymer solution's behavior due to the sacrificial agent's presence. An adsorption study was conducted with clays and crushed rock samples to determine the adsorption of a sacrificial agent and its effect on the adsorption of the polymer. Coreflood experiments were performed to determine the polymer retention and injectivity properties. The results obtained from the experimental study demonstrated the potential of the low molecular weight polyacrylate polymer as a sacrificial agent in minimizing polymer retention. The sacrificial agent did not alter the polymer rheology. The static adsorption test shows that the pre-adsorption of the sacrificial agent can reduce the polymer adsorption. The adsorption of HPAM polymer in Illite clay was 0.79 mg/gm without the sacrificial agent. It was reduced to 0.44 mg/gm in the presence of the polyacrylate about 56% reduction. The dynamic coreflood tests showed that retention can be reduced significantly by 50% - 70% in the presence of the sacrificial agent. This reduction in retention enabled quicker pressure stabilization, increasing injectivity, and had the added benefit of reducing the residual resistance factor by approximately 47%. The protective layer formed by the sacrificial agent effectively reduced the irreversible adsorption of the main polymer, thereby preserving its integrity and functionality. This study demonstrated that a small dosage of sodium polyacrylate could reduce the retention of polymers in low-permeability and clay-rich reservoirs. This treatment also increases the injectivity of polymers in clayey sandstone reservoirs. The properties of the liquid Na polyacrylate make it easy to use in the field during waterflood before starting polymer injection. Na polyacrylate can also contribute to scale prevention in and near the wellbore.