Comparative study of foam stability in bulk and porous media

Abstract

The oil recovery from a reservoir can be enhanced by gas injection. Creating a foam with the injected gas can improve the sweep efficiency. For an efficient foam displacement process the foam films must remain stable in the presence of oil. Unfortunately, most foams are destabilised by oil. It is therefore important to select an foaming agent appropriate for the reservoir. To select this foaming agent a reliable screening procedure is necessary. In this thesis seven different surfactant solutions were screened using three experimental methods (Interfacial and surface tension measurements, bulk foam tests and core flooding experiments). The different experiments are performed both in the absence and presence of a paraffin oil, at a temperature of 50ºC and atmospheric pressure. The bulk foam experiments were carried out with the Foamscan apparatus. All the foams were destabilised by the the oil, as predicted by the stability criteria about foam oil interaction. The rate of destabilisation is not accurately predicted and therefore the criteria have only limited applicability. The core flood experiments were performed using a Lilliput core, which had a diameter of one centimetre. This Lilliput core flood set-up proved itself as a good surfactant screening tool. Bulk foam stability and the apparent viscosity in the core correlate well, in the absence of oil, this indicates that bulk foam experiments are a useful screening tool to predict the surfactant performance in a core flood experiment. In the presence of oil the behaviour in core floods was more complex and no good correlation was found with the bulk foam experiments.