Abstract
This paper describes the mechanism for disproportionate permeability reduction (DPR). Recent papers have discussed possible DPR mechanisms. Most of the papers conclude that there is not yet a single factor that determines DPR. The intention of this paper is to clarify that there is a single model, which explains the observed DPR effects. This model relies on segregated flow of oil and water at pore level and on continuity in the oil phase at placement of the DPR fluid. With this model DPR is demonstrated for both gel and single polymer systems at different wettabilities. Oil continuity is normally easier to obtain for single polymers than for crosslinked gels. Gel systems may, however, be more robust. The paper describes a method for placement of water-soluble gel while maintaining open pathways for oil. Additionally, it is shown that using the phase permeability reduction ratio is not a good measure for defining optimum DPR. Therefore a new selectivity parameter is introduced which demonstrates to be more effective.
