Reservoir simulation of in situ electromagnetic heating of heavy oils

Abstract

The in situ electromagnetic heating (EMH) process is based on the concept that electromagnetic energy is transformed into heat energy by dielectric loss when an electromagnetic wave is transmitted into a reservoir. The heat results in a reduction in oil viscosity. EMH has been proposed and discussed in the literature but has not been tested in the field. This work was the first detailed reservoir simulation of oil production with EMH. A fully-implicit, single-well, two-dimensional, two-component reservoir simulator (EM model) was developed to model EMH of heavy oils. The electromagnetic heat source is modelled as a function of temperature and water saturation with the condition of constant pressure and temperature at the outer boundary. Heat conduction, convection, and three-phase fluid flow with vertical heat loss are fully implicit. A Jacobian matrix was developed to solve the system of heat and fluid flow equations by Newton iteration. Variable substitution was used in the simultaneous equation logic to maximize stability for a fixed amount of computation. The model was verified by a steady state model (EMSS model) and analytical solutions. As a result of the simulator runs, it was found that: 1. A "dry zone" can be created near the wellbore (when the connate water is vaporized) if enough EMH power is used. 2. When a dry zone is created, EMH increases the depth of heat penetration significantly. 3. When a dry zone is created, EMH results in 6.5 times the natural oil production rate as opposed to 2.0 to 3.5 times for electrical resistance heating. 4. When lower power levels are used, and a dry zone is not created, EMH results in about the same oil production rate as with electrical resistance heating. 5. EMH appears to be viable as an oil production stimulation process.