Rheological properties and the micromodel investigation of nanosilica gel-reinforced preformed particle gels developed for improved oil recovery

Abstract

Preformed particle gels (PPGs) in solutions have been widely used to suppress excess water production in mature oil reservoirs and, in turn, to improve the amount of oil recovery in brown oil fields. In this study, PPG solutions were meticulously formulated and synthesized in order to be utilized in harsh environments in terms of pressure, temperature, pH, and salinity from a free radical polymerization process.In this work, nanosilica gel at different weight percentages was added to improve the mechanical and thermal stability properties of the PPG at harsh condition: high pressure, temperature, and strain. Moreover, the effects of nanosilica gel at various concentrations, ranging from 0.0 to 1.0 wt%, on the PPG swelling properties in a 100,000 ppm brine along with the viscoelastic behavior of acrylamide copolymer (AM) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) with crosslinker of polyethylenimine (PEI) at 90 °C were studied. Having customized the formulation of the nanosilica-reinforced PPG, the solution was used to investigate the amount oil recovered in a water flooding process on a micromodel scale.The results for the recovery of oil obtained from the injection of PPG solutions were compared with those of water injection without PPG; i.e., the conventional water flooding. It should be stated that the microscopic images showed that nanosilica gel could affect the porous structure of the PPG and the X-ray Powder Diffraction (XRD) results confirmed the nanosilica particle distribution in the PPG pores with different diameters. Hence, the nanosilica-reinforced AM-AMPS/PEI with 1 wt% of the nanoparticles led in swelling of 8 g/g of the dried PPG. In addition, the strain sweep test at 90 °C suggest that increasing of nanosilica gel concentration from 0.2 to 1.0 wt% resulted in 3.34 times increase in the amount of elastic resistance of the PPG breakpoint and, thus, improvement in the complex modulus of initial PPG.In conclusion, the injection of PPG solutions, significant improvement in the oil recovery could be attained. The oil recovery factor increased from 32% under the conventional water flooding to 81% after injection of water with PPG containing only 1 wt% of nanosilica gel. Succinctly, the results confirmed that the tailored formulation had a great potential for field applications to enhance the oil recovery.