Electrical resistance heating (ERH) is a thermal stimulation technique in which electrical current passes through the formation. Field testing of this process is continuing. The current work uses results generated with reservoir simulation. Two models were used to describe ERH power dissipation (heating patterns):
a radial power model, and
an r-z power model.
Wattenbarger and McDougal developed a hand method for estimating the heated oil production rate under ERH stimulation. The production rate under ERH stimulation. The first objective of the current paper is to present improvements to that hand method. present improvements to that hand method. The new hand method has the following advantages:
downhole electrical power is estimated,
well damage is accounted for, and
accuracy of heated production rates is improved.
This new hand method can be quickly and easily used for screening potential ERH projects. potential ERH projects. The second objective of this paper is to present results from the r-z power model. The r-z power model provides a more detailed description of in situ heating patterns, including areas of intense heating (hot spots) which occur near the ends of the electrode. These hot spots may limit the amount of power that can be used in field installations.
The use of electromagnetic energy to stimulate heavy oil production his been reported as early as 1969. The mechanism by which heat is created is dependent on the electromagnetic frequency. At high frequencies (those between radio frequency and microwave frequency) dielectric heating dominates. Several papers on the topic of high frequency applications occur in the literature.
At low frequencies (less than 300 Hz), resistance heating dominates. Application of low frequency power is discussed in literature and can be called electrical resistance heating (ERH). Fig. 1 shows a diagram of the ERH process. Field testing of ERH is an ongoing activity and has been reported in the literature on several occasions.
Electrical resistance heating occurs when an electric current flows through the reservoir. The electrical energy is converted to heat. Because the electrical path is provided by in situ water, formation path is provided by in situ water, formation temperatures should be kept below the boiling point to maintain electrical continuity. The scope of the current work is limited to low frequency, single phase applications. The objectives are to provide an improved hand method for screening ERH projects, and to present the results of projects, and to present the results of detailed finite difference simulation study.
The hand method of screening ERH projects that is presented in this paper was projects that is presented in this paper was developed using a thermal reservoir simulator incorporating the radial power model to describe the in situ ERH heating pattern. The radial power model is a fully pattern. The radial power model is a fully implicit, single phase, thermal reservoir simulator. Fluid flow and current flow are 1-D radial. Heat losses to the overburden and underburden are 1-D vertical.