Throughout the lifetime of oil producing wells, a common problem encountered is excessive gas and/or water production. High producing gas-oil or water-oil ratio is normally responsible for both rapid productivity decline, and increase in operating costs caused by gas or water processing. The result is often a premature shut-in of wells because production has become uneconomical. Foamed gels have been used as selective barriers to counteract disproportionate gas-oil and/or water-oil ratios in oil production. However, knowledge of the effects of critical parameters such as wettability of the porous medium and pore geometry on foamed gel-blockage performance remains incomplete.
In this work micro-scale experiments, which involve the microscopic observation of flowing and trapped foamed gel in etched-glass micromodels were performed. The purpose of the research work is to provide new insights into the sensitivity of foamed gel blockage to porous media wettability and pore geometry.
The experimental results indicated that foamed gels present higher blocking efficiency in oil-wet systems than in water-wet systems. Under experimental conditions, foamed gels exhibit higher blocking efficiency at lower pore body to pore throat aspect ratios. The plugging treatment exhibits stability after subsequent steps of gas and brine injection. Ultimately, the combination of foam and gel has both technical and economic advantages that make foamed gels superior mobility control agents.
In porous media foam is a gas (or immiscible liquid) dispersed in a second interconnected liquid partially comprised of thin, surfactant-stabilized films called lamellae1. The surfactant used to impart stability to the mixture concentrates at the gas-liquid interface, to reduce interfacial tension and form stable lamellae. Foams are structured two-phase fluids that are compressible in nature2. In Fig. 1 a schematic representation of a two-dimensional slice of a general foam system is given. The general foam structure is contained on the bottom by the bulk liquid and on the upper side by a second bulk phase, in this case gas. The gas phase is separated from the thin liquid-film by a two-dimensional interface or lamella, which is defined as the region that encompasses the thin film, the two interfaces on either side of the thin film and part of the junction to other lamellae. The connection of three lamellae, at an angle of 120°, is referred to as the plateau border3.