Vitality of Natural Polymers in Safe Flooding in Offshore Operation: Road to Caspian Sea Implementation

Abstract

Application of Enhanced oil recovery methods (EOR) in offshore oil fields are getting more popular with the advancement in technology and chemicals used. Polymer flooding is one of the most successful projects to improve water mobility by increasing the viscosity. Application of polymers promises to improve areal sweep efficiency and consequently recovery factor. However the main concern associated with injection of chemicals in offshore oil fields is the possibility of leakage and pollution of marine systems affecting biodiversity and environment. The following study focuses on rheological properties of three bio-polymers: Xanthan gum, Wulan gum and Potato starch in laboratory conditions as viscosifying agents. The study involved characterization of each polymer at different concentrations from 500 ppm to 5,000 ppm dosage. Sensitivity analysis on various reservoir temperatures were also performed from 25°C to 55°C to fit Kazakhstan reservoirs along with sea water salinity to simulate Kazakhstan reservoir conditions. Results from rheological studies showed that 3,000 ppm is considered as the optimum concentration from Xanthan and Wulan gums, Potato starch did not show any good results as viscosifying agent. Further temperature effect studies showed that both Xanthan and Wulan gums have a strong temperature resistance and does not experience dramatic viscosity drop at reservoir temperatures in a range of 8-14% of loss. However, salinity effect showed that Wulan gum tends to lose rheological properties in high salinity environment and high viscosity drop. Rheological studies showed that Xanthan gum is highly resistant to salinity and temperature changes, while Wulan is only temperature resistant. The obtained rheological data were correlated with the Ostwald–de Waele power-law model to characterize fluid flow parameters, shear thinning behavior and identify n, k values. The correlations affirmed the shear-thinning properties of Xanthan and Wulan gums, a critical attribute for effective oil displacement in offshore reservoirs Core flooding experiments were performed for each polymer at the optimum concentration, salinity and temperature. Carbonate cores were used to simulate reservoir conditions and assess the effectiveness of natural polymers in improving oil recovery. Core flooding experiments with Xanthan and Wulan gums showed incremental oil recovery of 30 and 20% respectively. In the context of Kazakhstan's Caspian Sea, these findings herald a promising future for enhanced oil recovery, leveraging the robustness of natural polymers in challenging offshore conditions. Overall, these polymers demonstrated impressive results in displacing oil under harsh offshore reservoir conditions