Low-viscosity thermal-responsive epoxy emulsion for high-temperature and high-salinity reservoirs: Plugging characteristics and core displacement test

To overcome the temperature and salt resistance challenges faced by unconventional profile control agents in high-temperature and high-salt reservoirs. A novel low viscosity, temperature and salt stimulus response system named TRE was obtained by using emulsified epoxy resin and curing agent. Experimental work covers from core size to microscopic size to explore the effect and mechanism of enhancing oil recovery. A comprehensive analysis was conducted on the rheological properties, apparent viscosity, plugging ability, profile control capability, macroscopic oil displacement efficiency, and microscopic oil displacement mechanism of TRE emulsion. Our results indicated that the TRE exhibits temperature and salt responsiveness, with a salt tolerance of 7 x 10(4) mg/L and a phase change temperature of approximately 65 degrees C. Moreover, at a TRE concentration of 8 wt%, TRE showcased a lower injection viscosity of 1.3 mPa s. The microstructure after phase change was studied using SEM, and the irregular elliptical pore network structure enhanced its long-term thermal stability. Core displacement experiments were conducted to evaluate its plugging performance and profile control capability. The optimal plugging effect and injectability conditions were confirmed at an injection rate of 1 mL/min, an injection volume of 0.8 PV, and a TRE concentration of 8 wt%. As a profile control agent, TRE was well-suited for reservoirs with medium to low permeability, formation salinity ranging from 3 to 7 x 10(4) mg/L, and temperatures above 65 C-degrees, with a permeability limit of 180.2-720.1 mD. When the heterogeneity was below 9, the TRE exhibited a strong profile control effect, achieving a shunt rate of over 66% in low-permeability cores after plugging. Furthermore, macroscopic and microscopic oil displacement experiments indicated that TRE can effectively plug large and medium pores, and increase the coverage area of small pores. TRE has the advantage of plugging high permeability without complete plugging, which can effectively reduce reservoir heterogeneity and provide a uniform displacement. Following plugging, the swept volume by waterflooding increased by 18.46%, and the recovery rate increased by 19.10%. Temperature and salt responsive TRE exhibit excellent plugging ability, profile control capability, and oil displacement efficiency. Overall, this novel self-assembly system has potential for application in the exploitation of high-temperature and high salinity oil reservoirs.