Production improvement of heavy-oil recovery by using electromagnetic heating

Heavy oil is produced primarily by reducing its viscosity using well-known processes such as steam injection, steamsoak, and in situ combustion. A recent technique for recovery consists of resistively heating the reservoir using electrical energy. Resistive heating can be particularly beneficial for reservoirs in which conventional steam operations are uneconomic. Resistive heating is a special case of a more general form of heating based on electromagnetic energy (EM). EM has the following advantages over steam injection: it can be used to recover extremely heavy hydrocarbon, is not susceptible to heat losses through a wellbore, and its water requirements are far less than for steam. Compared to resistive heating, EM heats within the formation. Thus (for downhole generation) larger well spacing may be possible. Although its potential was recognized in the late 70's, there are relatively few field applications of EM heating and even fewer engineering studies. The purpose of this paper is to examine how the performance response of EM compares to resistive heating. This paper presents a model for single-phase flow to calculate the temperature distribution, and the productivity improvement obtained when an EM heating source (an antenna) is placed in a well. We consider both counter-current flow, in which the well with the antenna is also a producer, and co-current flow where the flow is opposite to EM energy flow. Flow is taking place concurrently with the addition of EM energy. Steady-state solutions for counter-current flow showed a relative productivity index (PI) increase of 2.5 - 12.0 times cold oil production when the input power was varied from 20 to 150kw. A peak improvement occurred when the adsorption coefficient was between 1e^-3 and 1e^-1 m^-1,*which indicates that there is an optimum adsorption coefficient. Resistive heating is the special case of an infinite adsorption coefficient and the existence of an optimum suggests that EM heating can be more effective than resistive heating. For co-current flow, the improvement was even greater for the same input power. Calculated energy gains (the ratio of produced to injected energy) were in the 8 to 163 range; successful steam injection processes have gains of around 10.