Characterizations of Disproportionate Permeability Reduction of Particle Gels through Fractures

Abstract

Abstract The primary objective of particle gel treatment is to significantly reduce water flow through high-permeability channels without damaging oil production zones. The ability of gels to reduce permeability to water much more than permeability to oil is a critical aspect of the success of water control in both production wells and in-depth fluid diversion conformance control. This work investigates factors affecting particle gel placement through fractures and determines the extent to which particle gels can reduce water permeability more than oil permeability within a fracture. Experimental models were designed to study the effect of the particle gel size, particle gel strength, fracture width, and oil viscosity on the disproportionate permeability reduction (DPR). Five-foot tubes with two internal diameters were used to represent a fracture with two different widths. PPGs were injected first into the fractures, followed by alternating floods of water and oil. During the gel injection, the resistance factors (Fr) increased as the gel particle size, gel strength, and fracture width increased. Results obtained from the alternating floods show that the DPR increased as the oil viscosity, particle size, gel strength, and fracture width increased. Gel shrinkage, gel strength, and gel dehydration were found to contribute significantly to this phenomenon. The permeability reduction factor to water increased, becoming 100 to 1700 times greater than the permeability reduction factor to oil. The injection pressure for different water cycles increased as more cycles were performed. These increases, however, were not significant when observed for different oil cycles. The experimental results show that when a second water cycle was injected to displace oil, the residual resistance factor for water (Frrw) in the second cycle was significantly less than the preceding Frrw values. This finding indicates that the gel experienced a significant breakdown during the first oil cycles. Additional oil cycles were performed, and the Frrw decreased during each new brine cycle, indicating further gel breakdown.