Multiphase fluid flow simulation of heavy oil recovery by electromagnetic heating

Electromagnetic (EM) heating, also called high-frequency heating, generates EM waves through an antenna located inside a wellbore and parallel to the reservoir sand-face. The EM energy heats the reservoir from within, causing oil viscosity to lower and oil production to increase. Recent studies (Carrizales et al. 2008) showed that oil rate can be increased with the application of EM heating for single-phase radial flow. No simulations results or detailed modeling studies have yet been published that completely model the complex interactions of EM energy and multiphase flow. This paper presents a multiphase, two-dimensional radial model that describes the three-phase flow of water, oil, and steam and heat flow in a reservoir within confining formations. The model accounts for the appearance and/or disappearance of a phase, and uses the variation in temperature and water saturation to continuously update the EM heating rate. A single well is used to locate the EM source, and also to produce oil. Gravity effects and vertical heat loss into the confining layers are included. This model allows determining the temperature distribution and the productivity improvement from EM heating when multiple phases are present. This model will be useful to predict the recovery of heavy oil by EM heating where conventional steam injection is not attractive. To solve the model we used Lagrange-quadratic finite elements in the environment provided by COMSOL Multiphysics and its partial differential equations (PDE) application. Several simulations were made for hypothetical reservoirs with different fluid and rock properties. Special attention is on reservoirs with characteristics for which steam injection does not look attractive or feasible. Results show the feasibility of conducting EM heating based on the power source and frequency used to maintain an optimum absorption coefficient and to obtain higher production rates avoiding excessive power consumption. Also, a comparison shows that cumulative oil production and recovery factor obtained by EM heating is better than what is achieved by cyclic steam stimulation (CSS), especially for thin payzones.