Modeling of Inversion Point for Heavy Oil-Water Emulsion Systems

Abstract

Abstract As the world's demand for oil increases, more heavy oil reservoirs are being discovered, drilled and produced. However, heavy oil production brings new challenges. One of the challenges is the formation of emulsions. Emulsions can cause high pressure losses, resulting in transportation and pumping problems and separation. The inversion point, at which continuous and dispersed phases in an emulsion changes, needs to be studied to improve knowledge of heavy oil-water emulsions. A new mathematical model was developed in this study using fundamental thermodynamics and conservation of mass laws to predict the inversion point of an emulsion system. Simulation results indicate that the properties of surfactant, emulsion droplet size and standard chemical potentials of the liquid phases play very important role in controlling the inversion point of an emulsion system. The model proposed in this paper can help predict inversion point of an emulsion system. Estimation of inversion point of emulsions helps improve the existing emulsion viscosity correlations and develop new models when necessary. The improved heavy oil-water emulsion viscosity models can be used in design and operation phases of heavy oil fields. Introduction The viscosity of heavy oil-water emulsion can be several orders of magnitude higher than the pure oil viscosity at certain conditions. Therefore, it is crucial to estimate the viscosity of emulsions for the operating flow conditions. One of the earliest studies of viscosities of suspensions and solutions is that of Einstein (1906, 1911). He proposed an emulsion viscosity correlation based on the ratio of emulsion viscosity to the viscosity of continuous phase. The proposed correlation is: Equation (1) where ?r is the ratio of viscosity of the emulsion to viscosity of the continuous phase, and fint is the volume fraction of the dispersed or internal phase. The equation is valid for dispersed phase volume fractions up to 0.2. Therefore, it can only indicate the trend at the origin. Brinkman (1952) presented a very simple method to estimate the viscosity of concentrated suspensions and solutions. He studied the change in viscosity by adding incremental amount of spherical molecules to the pure solvent. He proposed a correlation for viscosity of concentrated suspensions and emulsions as follows: Equation (2) Dougherty and Krieger (1972) assumed that maximum packing of droplets occurs at the inversion point of the emulsion, and proposed the following correlation for emulsion viscosity ratio: Equation (3) where fpack is the volume fraction of the dispersed phase at close packing.