Lack of steam injectivity is one of the most serious obstacles in the thermal recovery of tar sands and oil shale deposits. Electric heating offers a technically viable option which has been the subject of studies and field tests in the last 10 years. This paper discusses the application of electric heating to reservoirs with electric resistivities ranging from 100 ohm-m (tar sands) to 10,000 ohm-m (oil shales). A numerical model is constructed to solve Maxwell's electromagnetic field equations.
The model is used to study the electric preheating of a tar sand reservoir using horizontal electrodes to develop steam injectivity. After preheating, electrodes are converted into conventional injection/ production wells to be used in a subsequent steam recovery process.