Finite Element Modeling of Reservoir Heating By An Electrical Cable

Abstract

Heat, mostly in terms of steam latent heat of vaporization, has been injected into heavy or extra heavy reservoirs worldwide to assist producing the in-situ oils. More recently, heat has been introduced directly into the reservoir by means of placing an electrical cable at the middle of the well in front of the target interval. Design of these electrical cables which supply a specific amount of heat energy per cable length, W/m, when placed in front of the target zone, have been evolving from manufacturing point of view to benefit oil operations worldwide in many ways. The purpose of this study is to investigate the heat transfer effects from the electric cable into stagnant gases of the wellbore media, casing, and reservoir porous media which are surrounding the electric cable. Two types of wells, vertical and horizontal have been studied. The objective is to calculate heat requirement to establish desired temperature distribution beyond the sandface. The mathematical model used to study the heat transfer effects were built by a finite element model software package. In case of cased hole, the heat transfer from the cable propagates through stagnant gases and enters the casing before entering the porous media. In case of open -hole completion, the heat from the cable is transferred to stagnant gases in the wellbore before entering the porous media. Effects of different heating amounts in W/m on the sand-face temperature and deep into the porous media have been investigated for vertical and horizontal well configurations at different energy input conditions. Finite element model results were compared with other similar studies. Results of the finite element modeling show that for all cases including vertical and horizontal wells, the sand-face quickly heats up. As time goes on, a distance into the porous media is also heated up which in return assists oil recovery from a larger vicinity from the well. Heating via electric cables can be beneficial in wellbore cleaning from paraffin, wax and hydrate build ups thus initiating oil recovery from near wellbore area. Total reservoir heating can provide In-situ upgrading of the heavy and extra heavy oils.