In the electrical joule's heating process, the reservoirs are heated in situ by electrical energy to reduce the viscosity. In principle, electrical current passes through the reservoir fluids due mostly to the electrical conductivity of saturated fluids such as saline water. The flow of electrical current through the reservoir leads the heat in the reservoir and thereby drastically reduces the oil viscosity.

In this process, electrical current can flow between electrical potential sources (wells) and generate the joule's heat. Therefore, the regions around the electrodes in (or around) the wells are extremely heated. Because the wells act as line sources for the electrical potential, greater heating takes place near the wellbore causing possible vaporization of water in that region. Since steam has very low electrical conductivity, it can reduce the efficiency of this process significantly. In this process electrical conductivity plays a very important role. In order to increase efficiency of this type of heating process, the presence of optimum saline water saturation is an essential design factor.

In order to simulate a challenging multiphysics problem, we use three Maxwell classical electromagnetism equations. These equations are simplified and assumed for low frequency to obtain the conservation of electrical current equation and Ohm's law. The conservation of electrical current and Ohm's law are implemented using a finite difference method in a four phase chemical flooding reservoir simulator (UTCHEM). The joule's heating rate due to electrical current is calculated and added as an energy source to the energy balance equation.

A typical reservoir model is built and constant electrical potential with alternating current (AC) is applied to this model to study the efficiency of the electrical joule's heating process in the presence of water saturated fracture and evaluate this efficiency at, above, and/or below the water boiling point. Results illustrate that water saturation in the presence of fracture and electrical conductivity of saturated rock have an important effect on the joule's heating process. In this paper, we show that since, steam is a non-conductive electrical phase, this process should be designed to keep the temperature below the boiling point by circulating water. This can prevent the evaporation leading to an increase in the process efficiency.

Electrical conductivity of water can also be easily increased by injecting high salinity water into the reservoir and increasing the amount of heat substantially. This is highly beneficial and the main advantage of the electrical joule's heating process that can obtain high recovery in comparison to other thermal recovery methods. In this paper the understanding of the influence of saline water and steam forming is a key finding in order to economically optimize the process to unlock heavy oil reservoirs.

You can access this article if you purchase or spend a download.