Profile control and oil displacement in high temperature and salinity reservoirs: Evaluation of deformable microgel system

Viscoelastic microgels have been successfully used as profile control and enhanced oil recovery agents in oil reservoirs. In this paper, a novel microgel made of acrylamide monomer and 2-Acrylamido-2-methylpropane sulfonic acid was synthesized using inverse emulsion polymerization. The spherical shape of microgel particles and their corresponding size distribution were confirmed by series of microscopic images. Additional tests such as morphology and swelling tests indirect characterization of structural properties via rheology tests, and viscoelastic tests of spherical microgels were performed for 5 different aqueous solutions. The flow curve of all aqueous solutions illustrated three areas of shear thinning, static state, and shear thickening representing presence of dispersed system and confirming formation of microgel suspension. According to results of the oscillatory frequency sweep test "superior" viscoelastic properties were demonstrated. Also, no structural fracture occurred in the frequency range of 0.01-100 Hz with elastic modulus of 105, 3.63, 2.4, 3, and 1.6, respectively. Furthermore, excellent swelling properties were observed in presence of monovalent, divalent ions, and brine. In addition, performance of microspheres microgel suspension (MMS) in formation water were evaluated using a micro and macro floodingexperiment setup. Due to the elastic modulus of microgel system (2.4 Pa) and its viscoelastic properties, deformation capability and the ability to maintain initial shape of microgels, the oil recovery was increased to 83.77, which was 2.02 times more than that of water flooding displacement. The MMS macro-flooding test indicated the alteration of the core from oil-wet to water-wet. Also, the pressure drop created during water injection compared to during oil injection increased from 0.67 to 9.62 after treatment with MMS. The characteristics and displacement performance of a deformable microgel make it a good candidate for in-depth gel treatment and sweep efficiency improvement.