Abstract In crude oil production, the generation of heavy oil/water emulsions can result in a significant drop in the production rate due to the high viscosities of the emulsions. The strong agitation and mixing that takes place at the inlet of the well bore together with the presence of the naturally existing emulsifying agents in the crude contribute to the formation of the emulsion. A number of methods can be used to mitigate this problem such as the injection of surfactants into the formation and surface treatment. The objective of this paper is two-folds. Firstly, the results of an experimental program carried out to evaluate the efficiency of several surfactants to demulsify crude oil / water emulsions are presented. Secondly, a novel cost effective technique for injecting the surfactant into the well utilising existing gas lift facilities at the well heads is described together with a number of other techniques which have been tested for treatment of emulsions.
The experimental study was performed on crude oil/water emulsion samples obtained from two sandstone reservoirs in the Bahrain field. The measurements included effects of surfactants on the degree of demulsification, surface tension and shear viscosity. An optimum surfactant/emulsion volume ratio of around 1.5 to 2% was noticed in most cases for the specific wells investigated. The addition of surfactants considerably reduced the shear viscosity and surface tension of the emulsion. As expected the surface interfacial tensions decreased with increasing temperature.
Introduction Oil-water emulsions are formed during the process of crude oil production. It has always been a challenging task to efficiently break-up this emulsion to separate the oil from water at various stages of the oil production process, starting from the well bore, where heavy emulsions can seriously reduce the production rate, as well as on the surface, where maximum amount of oil/water separation is required both from production and environmental perspectives. Formation of interfacial films results in the adhesion of the crude oil to water-wetted hydrophilic surfaces and can seriously distort the flow pattern in small capillaries [1]. Several methods can be used to separate crude oil from water such as surfactants, heating and centrifugation. Using surfactants is the most effective method that is commonly used during the oil production process to demulsify the oil-water emulsion [2].