A New Foam Model in Pipes for Drilling and Fracturing Applications

Abstract

Summary A series of recent experimental studies revealed that foam flow can be represented by two distinct flow regimes in general—low-quality regime, showing stable plug-flow pattern, and high-quality regime, showing unstable slug-flow pattern. This study, for the first time, presents how to develop a comprehensive foam model that can handle a variety of bubble-size distributions and both stable and unstable flow patterns with a two-flow-regime concept. Building an improved foam model on the basis of such a new concept can potentially help to better design and optimize many foam-associated processes including tight-gas and shale-gas foam fracturing, foam underbalanced drilling, foam liquid unloading, and cuttings transport. Analyzing the experimental data of surfactant foams and polymer-added foams shows that (i) in the low-quality regime, foam rheology is governed by bubble slippage at the wall with no significant change in its fine foam texture and (ii) in the high-quality regime, foam rheology is governed by the relative size of free-gas segment to fine-textured foam-slug segment. With these governing mechanisms, this improved foam model successfully reproduces foam-flow characteristics as observed in the experiments, including almost-horizontal pressure contours in the low-quality regime and inclined pressure contours in the high-quality regime. Although the model is built with a power-law fluid model, the same procedure can be applied for Bingham-plastic or yield-power-law fluids.