Comparative Analysis of Electromagnetic Heating Methods for Heavy-Oil Recovery

Abstract

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 150550, ’Comparative Analysis of Electromagnetic Methods for Heavy Oil Recovery,’ by Igor Bogdanov, SPE, Jose Antonio Torres, SPE, and Arjan Kamp, SPE, CHLOE, and Bernard Corre, CSTJF-Total, prepared for the 2011 SPE Heavy Oil Conference and Exhibition, Kuwait City, Kuwait, 12-14 December. The paper has not been peer reviewed. Thermal methods are well-known for enhancing oil recovery by decreasing reservoir-oil viscosity substantially by raising the temperature. Although it is one of the more popular thermal methods, steam injection is not always applicable successfully in real reservoir conditions because of prohibitive heat losses from injection wells and reservoirs, low reservoir injectivity (especially for bitumen deposits), steam leakage, and other environmental problems. Fortunately, a good alternative to steam injection exists—electromagnetic heating (EMH), which includes a variety of methods. Introduction Different physical mechanisms, according to the frequency of the electromagnetic (EM) field, are responsible for the heating. For instance, low-frequency heating (LFH) is based on the Joule effect. Inductive heating (IH) is the process where Foucault (eddy) currents generated within a load also result in Joule heating. Finally, high-frequency heating (HFH) consists of in-situ dielectric heating from rotation with friction of polar molecules in the EM field. An EM field facility is installed normally in a wellbore; the EM power is converted into heat inside the reservoir, leading to an increase of local temperature. The advantages of EMH methods—avoidance of low-injectivity/-connectivity and injection-pressure-related problems—are complemented by in-situ heat generation and, particularly, water evaporation (e.g., during HFH). The common physical nature of the phenomena under consideration explains similar features in the EM-field distributions. Consider, for instance, that each method has a nearly singular electric field close to the source, which depends on both the source geometry and the frequency of EM waves. Another common point is that these techniques are efficient only if some critical amount of connate water is present initially in a reservoir. Water’s electric properties make the methods applicable for a wide range of reservoir conditions. LFH differs from the other two methods in that its use is limited by the existence of an effective electrical circuit—in other words, LFH requires continuous conductive paths for electric current between electrodes. This means that the reservoir water must always be liquid around the electrodes. If it is not, the electrical circuit will be disconnected, and no electrical current means no heat. For IH and HFH, this is not true because the EM waves propagate (without absorption) through a dry porous medium. However, as in LFH, no heat is released in the dry medium.