Preparation and mechanistic analysis of high-selectivity water control systems

Abstract

This paper presents a highly selective water control system designed to address declining oil production in offshore wells caused by rising water cuts while overcoming the poor selectivity of current chemical water control materials. The system was developed by copolymerizing octadecyl methacrylate and butyl methacrylate, followed by emulsion polymerization to prepare oil-soluble polymers. This resulted in a water-dispersible, high-selectivity water control system in the form of an emulsion dispersion. The feasibility of its field application was assessed via median particle size and reservoir stability tests, and the system's water control performance, visual performance, and underlying mechanism were evaluated. The test results showed that the median droplet diameter of the emulsion in the system was 0.431 μm, and it remained stable for at least 8 h under reservoir conditions. The system demonstrated excellent selective water-control capabilities, with a water-phase permeability blocking rate of 82.42% and an oil-phase permeability blocking rate of 5.02%. The mechanism of action was further explored via visualized flat plate tests and low-field nuclear magnetic resonance scanning displacement experiments on rock cores. The findings suggest that oil-soluble particles exhibit effective selective water-control performance and can be applied in water control operations in offshore oil fields.