Novel in-depth profile control agent based on in-situ polymeric microspheres in low permeability reservoir

Abstract

To solve the contradiction between the injectability of the profile control agent and its profile control ability in low-permeability reservoirs, a novel in-situ polymeric microsphere profile control agent is proposed. In-situ-polymeric microsphere (ISPM) emulsion was injected into the formation by polymerization to form microspheres for profile control. The emulsion was composed of divinylbenzene, acrylamide monomer, surfactant fatty acid polyoxyethylene ether sulfate, sorbitan oleate and p-hydroxyanisole. An ISPM particle diameter of 1.88 to 30.60 μm was achieved by adjusting the amount of Span80. The ISPM emulsion polymerization time was set to a maximum of 8.4 hours to ensures that the microsphere emulsion could be successfully injected into the formation. Polymerization reaction time increased with the increase of salinity. pH has no significant effect on the reaction time in the range of 5 to 8. Fourier transform infrared spectroscopy (FT-IR) experiments showed that the ISPM emulsion could be polymerized in tiny pores to form microspheres. Furthermore, multipoint pressure measurement experiment and electron microscopy results showed that the ISPM emulsion presented good injectability in low-permeability cores, and the microspheres formed after emulsion polymerization achieved deep plugging in cores. The injectability and blocking effect of the core with ISPM was found to be better than with microspheres (61.7%) for the blocking rate of the core at 10–15 cm deep reached 81.55%. The double-layer heterogeneous core flooding experiments showed that ISPM could expand the sweep volume of subsequent injection fluids and achieve improved oil production and water control. The composite slug composed of surfactant BA and ISPM demonstrated better profile control effect than the ISPM slug alone, and the enhanced oil recovery factor reached 15.65%.