Investigation on the Slow Release Viscosity Increasing Characteristics and Oil Increasing Mechanism of Encapsulated Polymers in Heterogeneous Reservoirs

Conventional polymers are typically injected into the reservoir to enhance the oil recovery. However, their molecular chains are susceptible to shear-induced scission during injection. This phenomenon reduces the polymer viscosity in internal reservoir zones. To address these limitations, an encapsulated polymer has been developed. Upon exposure to reservoir conditions (such as temperature and salinity), the capsules rupture to release polymer emulsions, facilitating controlled viscosity enhancement in the target zones. In this study, we established a mathematical model to characterize the release rate and viscosity variations of encapsulated polymers under the constraints of reservoir conditions. Subsequently, a numerical simulation model was developed to describe the postinjection behavior of encapsulated polymers, including their controlled rupture/release mechanisms and viscosity enhancement processes in internal reservoir zones. Finally, the impacts of injection strategies on seepage resistance and polymer injection volume were investigated, enabling the optimization of injection parameters under diverse geological conditions. The results indicate that encapsulated polymers exhibit excellent long-distance transport capacity in the reservoir. They also maintain a higher viscosity retention rate in the reservoir and demonstrate superior flow control during development. Compared with conventional polymer flooding, encapsulated polymer flooding increases oil recovery by 2.94%, yielding favorable results in enhancing oil recovery efficiency.