The Rheology of Foam

Abstract

Abstract Both experimental and theoretical analyses were carried out on the rheological behavior of foam. This foam was generated by simultaneously injecting compressed air and an aqueous solution of a commercial foaming agent into a short porous medium. It then flowed into a capillary tube viscometer having four interchangeable glass tubes of different radii. A mathematical analysis was developed whereby both the very pronounced effects of fluid slippage at the tube wall and the foam compressibility were taken into consideration. The apparent viscosity was independent of foam quality but not of tube radius. Bubble size and bubble size distribution were measured under a microscope and the change of bubble size with-time studied through photomicrographs. Both the mean bubble diameter photomicrographs. Both the mean bubble diameter and bubble size distribution were functions of foam quality. The cumulative size distribution as a function of a quality is represented by a modified Weibull function. Although the flowing foam behaved like a pseudoplastic fluid, the static foam had a pseudoplastic fluid, the static foam had a measureable gel strength which increased with foam quality. Introduction Foam is a gas-liquid dispersion in which the liquid is the continuous phase and the gas is the discontinuous phase. It occurs widely and is used in many industrial applications. In the petroleum industry, foams are often encountered in gas-oil separators. In recent times, aqueous foams have been used in several oil field applications such as removal of brine from low pressure gas wells and as a drilling and completion fluid in low pressure, water sensitive reservoir rocks. Their use has also been proposed to plug thief formations and to seal caprock leaks in underground/natural gas storage reservoirs, and as a displacing agent in conjunction with water floods. Some of these applications are involved with foam flowing through tubes or pipes whereas others are concerned with the flow or retention of foam in porous media. porous media. The many physical properties of foam have been described by scientists and engineers in numerous papers and these are reviewed elsewhere. The many papers concerned with the flow properties of foam are particularly pertinent properties of foam are particularly pertinent to its use in petroleum production. In these, foam is usually considered as a fluid, which is probably a valid assumption if the bubble size is small compared to the instrument's dimensions or the size of the fluid conduit.