Development and application of the emulsion polymer/ core-shell microsphere profile control system

Pathways for moderate–strong water channeling are gradually formed in deep zones of the medium–low permeability sandstone reservoirs in the Bohai Sea during during water flooding. The conventional polymer microsphere system cannot facilitate profile control and plugging and present desired injectivity in sandstone reservoirs. To solve this problem, the emulsion polymer + core-shell microsphere profile control system that can form network structures in deep formations was developed. Laboratory tests were performed to investigate the viscosity variation, particle size variation and dynamic transportation in porous medium of aggregates of the comoposite system. The results show that the comoposite system composed of emulsion polymer solution (hydrolysis degree = 30%) and core-shell polymer microspheres (core-shell charge ratio = 1∶3) with the mass ratio of 0.0646∶1 has the viscosity of 18 mPa·s and the particle size of 102 μm, and can rachieve the plugging efficiency up to 86.6%. The field application of this system in the S cluster of the Bohai B oilfield demonstrates that the oil production increment of the cluster exceeds 5 600 m³, the maximum decrease of water cut is up to 7%, and the effective duration lasts for more than six months, which indicate the good performance of water control and production enhancement.