Abstract

Conventional steam injection processes for thermal heavy oil recovery are generally limited to relatively shallow, thick, permeable, and homogenous reservoirs. An alternative thermal recovery process is to use electromagnetic (EM) energy to generate heat. Radio frequency heating is one type of EM heating, which is based on wave propagation phenomenon and uses high frequency EM sources. Due to these characteristics, RF heating can provide a controllability aspect of the thermal process by which heating pattern can be steered toward an area of insert and being turned away from a particular region. This can be achieved by combining the EM fileds of multiple RF sources (antenna) in an array configuration.

Although EM heating for heavy oil recovery is not a new idea, a commercial application still requires detailed modeling and a more quantitative analysis due to the complexity of the multiphysics process involved. In this paper, we first review the physics of EM heating of a subsurface formation followed by providing closed form correlation models of previously introduced data on electrical properties of Athabasca oilsands. We then revisit some of the analytical models of RF heating mechanism proposed in the past by evaluating the effect of far-field approximation on the accuracy of RF power deposit calculations. Important considerations for antennas being employed for RF heating applications such as near-field criterion and the effectiveness of bare versus insulated antenna will be discussed afterward. Finally, with few examples using analytical modeling, we provide a proof of concept for the method of using an antenna array for directing the RF-thermal pattern in an oilsand formation.

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