Recovery Of Athabasca Bitumen With The Electromagnetic Flood (Emf) Process

This paper presents a conceptual description of a process (the Electromagnetic Flood process or simply EMF process) for inundating an oil sand formation with a guided electromagnetic wave to generate a heat front penetrating into the formation, thereby generating a heat zone of low-viscosity bitumen which is suitable for in-situ recovery. A first-order numerical model has been developed to examine the proposed healing and production for the case where production occurs through unassisted natural gravity drainage. A brief description of the model and the results of some typical simulations are included. Introduction The Alberta oil sand deposits represent a very large heavy oil reserve. Unfortunately, only a small fraction of the identified deposits are located close enough to the surface to allow recovery by current strip mining techniques. A great deal of effort has, therefore, been directed toward devising methods of recovering deeply buried bitumen directly from the formation without mechanically removing the sand. Many in-situ recovery methods have been proposed. Most operate on the premise, that if the tar-like bitumen in a formation can be heated well above its ambient temperature of 10 to 15 degrees Celsius, its viscosity will drop sufficiently for the bitumen to flow through the native sand bed and be collected. The major difficulty encountered in such thermal schemes is that of adequately transferring large amounts of energy into the formation in a controlled manner and within an acceptable period of time. Electrical heating schemes operating at various frequencies have been suggested(1–6) as a means of obtaining the desired energy transfer. The process proposed here involves inundating the formation with an electromagnetic flood (EMF) to obtain the necessary energy transfer while producing the formation using gravity drainage. Generating an Electromagnetic Flood with Gravity Drainage A number of possibilities exist for applying electromagnetic wave energy to the formation. For the purpose of describing the operation of an EMF a rather specific scheme will be considered. What is proposed would be a mine-assisted drilling process whereby a plurality of horizontal wells are drilled into the formation at the bottom and near the top of the payzone (Fig. 1). These wells would be perforated such that they may serve as injectors or producers, as well as high-frequency electrodes. Attaching a high-frequency power source between the upper/lower electrode pairs will result in the generation of an electromagnetic wave travelling from the source horizontally into the payzone, and the generation of a heat front which also moves horizontally into the payzone area. This moving heat frontinduced by the electromagnetic wave is what the authors refer to as an EMF. The electrode wells serve to guide and constrain the EMF so that heating occurs predominantly in the desired payzone area. As the wave propagates into the lossy formation a fixed portion of its residual energy at any given point is delivered to the formation over the next unit length of travel. Most of the energy is thus deposited near the wave source and the energy deposition tends to be as shown in Figure 2.