This paper compares three recent different independent research projects on experiments and modelling of the use of surfactants to create a foam for deliquification of wet gas wells. The research groups involved are TNO, Delft University of Technology and the University of Tulsa. The various experimental setups that are used and their outcome (trends and correlations) are described. In each project, a model was developed to predict the pressure gradient under foam flowing conditions. These models are discussed here and they are applied to representative well conditions.
Liquid loading is a well-known problem that occurs when wet gas wells approach their end-of-life. Due to the depletion of the reservoir, its pressure decreases. Consequently, the gas flow rate in the well is also reduced. When only dry gas is present in the well, the reduced gas flow rate has no further effect. However, when a liquid phase is present (condensate and/or water) the reduced gas flow rate may, at some point, no longer be effective in transporting the liquids to the well head and they will accumulate downhole; this is the so-called liquid loading or liquification. The critical gas velocity, Ucrit, where the pressure gradient is minimized with respect to the gas flow, is often used to determine the onset of liquid loading.