Applications of in situ polymerization microsphere with surfactant EOR in low-permeability and heterogeneous reservoirs

In order to enhance the low recovery efficiency in low-permeability and heterogeneous reservoirs resulted by water channeling during water flooding process, a series of flooding experiments using in situ polymerization microsphere (ISPM) with surfactant were conducted to achieve deep profile control in high conductivity water channels. Dynamic pressure measurement showed that ISPM demonstrated good injectability and profile control effect in low-permeability core of 20.22 mD, as the plugging rate was as high as 78.99%. At the same time, the electron microscopy results showed that the ISPM could migrate deeper into the core to form microsphere clusters to block the high conductivity channels. The core flooding experiments showed that the profile control effect of the composite slug consisted of surfactant and ISPM was much better than that of just ISPM alone. The front part of the slug consisting of BA with strong emulsifying capability and ultra-low interfacial tension can better exert the profile control effect of the ISPM and expand the sweep volume of the subsequent displacing agent better than surfactant TS with ultra-low interfacial tension. As a subsequent oil displacing agent after ISPM + BA profile control, surfactant BA with strong emulsifying capability and ultra-low interfacial tension, compared with AES and TS, achieved higher recovery efficiency. In low-permeability and heterogeneous reservoirs, ultra-low interfacial tension is screening crucial characteristic of surfactant, but emulsification capacity also plays a very important role. Combination of surfactant BA and ISPM could fully utilize the profile control effect of ISPM and the oil stripping effect of surfactant; the stage recovery efficiency was as high as 22.52%.