Oil Production Response To In Situ Electrical Resistance Heating (Erh)

Abstract

An oil well can be stimulated by applying AC current to the formation in a single well. This type of stimulation can be called electrical resistance heating (ERH). The viscosity reduction which resultsfrom a higher temperature around the wellbore increases the oil production rate. This process has been tested in thefield and the performance successfully matched with reser-voir simulation. This study was performed to find a simple method of estimating steady state stimulated production rate.A two-dimensional simulator was developed and run for 52 cases which covered a variety of reservoir conditions. This sen-sitivity analysis showed thatfourparameters accountedfor most of the variation in production rate. The parameters were ini-tial oil viscosity, formation thickness, drainage radius and induced temperature change.Thepredictive equation takes theform ofsteady-state radial Darcy's Law with a modified oil viscosity term. The modified oil viscosity is a weighted average between the initial oil vis-cosity and the minimum oil viscosity at the wellbore. The weight-ing factor was matched to the reservoir simulation results by regression analysis. The use of this simple predictive equation agrees well with simulation results for steady state j7ow. Introduction Oil production can be stimulated by applying electrical power in the formation. The electrical power causes a temperature in-crease which reduces oil viscosity and results in increased oil production rates.Electrical energy is converted to heat in the formation by a combination of electrical resistance heating (ERH) and electro-magnetic power absorption, depending on the electromagnetic power frequency. This study was confined to electrical resistance heating (ERH), which is the major source of heating when low frequency (60 Hertz) AC electric power is used.The literature reveals several papers dealing with the possi-bility of using the ERH process for stimulating oil recovery,'-1). Pilot studies have also been initiated in Canada, United States, Mexico, and other countries with varying degrees of success(1,3,6,7). One of the earliest examples of electrically stimulating oil recovery was reported by World Oil in 1970(l). The method was designated as the "Electrothermic Heating Process". The Keywords: Stimulation, Simulation, Heavy oil, Electrical heating, Ther-mal recovery. Paper reviewed and accepted for publication by the Editorial November-December 1988, Volume 27, No. 6 process used an AC current applied around the wellbore. The heat was reported to improve production of low APT gravity Oils uP to 300%. Single-phase AC electric power was used to avoid metal corrosion associated with DC electric power. _ Flock and Tharin(2) mentioned mufti-well ERH as a possi-ble recovery method. They proposed using electrically heated water in secondary recovery projects to increase displacement efficiency. They also pointed out poor efficiency in electric pow-er generation was a major drawback to the ERH method. As a result, Flock and Tharin considered ERH as a preheat for mo...