Energy producing companies increasingly exploit non-conventional hydrocarbon resources such as heavy oil, bitumen or shale. Because of their large viscosity, production of oil from such resources is frequently done through reservoir heating, most often via steam injection. In some cases the steam injection is not a good alternative, especially, for tar sands. A better suited technology may be electromagnetic heating (EMH) assisted oil recovery.
Different physical mechanisms underlie the heating according to the frequency of electromagnetic (EM) field. For instance, low-frequency heating (LFH) based on the Joule effect is well-known for environmental applications and has been field-tried recently. So-called inductive heating used for many years in induction furnaces is the process where Foucault (eddy) currents generated within a load result again in Joule heating. Finally, high-frequency heating (HFH) consists of in-situ dielectric heating resulted from rotation with friction of polar molecules in the EM field.
An EM field facility is installed normally in a well bore, the EM power being converted into heat inside reservoir which leads to the increase of local temperature. The conspicuous advantages of all EMH methods – avoidance of well low injectivity/connectivity and well injection pressure related problems – are complemented with in-situ heat generation and particularly, water evaporation (e.g. during HFH). Nowadays, according to literature sources, the EMH models of two types are in use. The first one is a class of analytical approaches using relatively strong assumptions mainly concerning to heating power distribution. They provided reference solutions for numerical models and an order-of-magnitude estimation procedure which is feasible for large-scale models.
Being geometrically more complex the large-scale models have been developed for simulation of more realistic EM power distribution. These models provided a framework to critically analyze the processes of oil recovery. The obtained numerical results are used for subsequent consideration of advantages and application limits for each of considered EMH methods, i.e. for low- and radio-frequency heating assisted heavy oil recovery.
The comparative analysis of different methods of EMH assisted oil production provided by this work is an important feature in process design considerations.