Enhancing xanthan hydrogels for water shutoff treatment in sandstone oil reservoirs through core flooding and CCD approach.

This study examines the efficacy of xanthan gum, as a natural polymer, in creating a suitable hydrogel for controlling water production in reservoirs. The study employed the Central Composite Design (CCD) method through bottle tests to evaluate the effect of different compounds on the gelation time and duration of syneresis. To explore the effectiveness of the xanthan-based hydrogels, swelling tests as well as dynamic core flooding tests are performed. Additionally, to enlighten the performance of the xanthan hydrogels, comprehensive set of characterization tests are performed. Nevertheless, the swelling test results indicated that increasing the polymer concentration led to an increase in swelling. SEM images of the dried hydrogel confirmed the structural integrity and uniformity of the networked architecture, demonstrating an increase in thickness and density. Furthermore, four hydrogel samples with the most appropriate specification in the bottle and swelling tests were chosen for core flooding tests. The results demonstrated that injecting the sample including; polymer@8000ppm, crosslinking agent ratio@0.15, and nanosilica@0.05 wt%, as an optimal sample, caused a 71.9% decrease in water production. Finally, the residual factor of 2.289, indicated the effective efficiency of xanthan-chromium hydrogel in the presence of nanosilica to reduce water permeability compared to oil in sandstone reservoir.