Determination of Permeability Contrast Limits for Applying Polymer Solutions and Viscoelastic Particle Suspensions in Heterogeneous Reservoirs

Abstract

Polymers and viscoelastic particles are the main chemical agents used to improve water injection profile and thus increase oil production. In actual formations, however, there is a lack of knowledge on selecting an appropriate chemical agent to achieve excellent conformance control and oil production performance. To address this issue, this paper first investigated the main rheological properties and resistance increase performance of the two chemical agents. After that, the permeability contrast limits for applying polymer solution and viscoelastic particle suspension in heterogeneous reservoirs were determined through shunt flow experiments. The critical impact of permeability contrast limits on chemical enhanced oil recovery (EOR) was further verified via a two-dimensional (2D) visualized oil displacement experiment. It was found that the particles exhibit superior elasticity, while the polymers mainly exhibit a viscosity increase effect. The resistance increase capacity of the particle suspension in the core was more potent than that of the polymer solution, which results in its excellent conformance control in strongly heterogeneous cores. On the contrary, the polymer solution might face the risk of failure. The permeability contrast limits for applying the two chemical agents at different concentrations were determined. Visualized oil displacement experiments showed that the EOR by polymer flooding in strongly heterogeneous reservoirs is quite low (3.3%). In contrast, the particle suspension could effectively expand the swept zone and extract considerable remaining oil in the low-permeability zones. Accordingly, the EOR could reach 7.1%. Determining permeability contrast limits is of practical significance for selecting suitable chemical agents to realize successful conformance control and oil extraction in heterogeneous reservoirs.

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