Abstract

Most of the world hydrocarbon reserves represent extra-heavy oils. Exploitation of most of these reservoirs has not been carried out mainly due to the difficulty to produce the high-viscosity of extra heavy oils. Cold production can be achieved in the Orinoco Oil Belt through advanced horizontal wells. However, in many cases the drawdown exerted creates gas or sand production problems or excessive water production when an aquifer exists. Primary recovery factor under these conditions rarely go beyond 6%; and 3% in the presence of an active aquifer.

On the last decade several thermal mechanisms have been studied to increase the recovery of these types of reservoirs. This study analyzes the effect of bottom-hole electric heating on the production and recovery factors of extra-heavy oil reservoirs. The study was carried out by numerical simulation, analyzing the most influential parameters through an experimental matrix of 24 cases run in a horizontal well of 2000 feet. Four types of oils were studied, 8.1, 10, 12 and 15°API gravity. Reservoir thicknesses used were 300 feet and 80 feet. Two different heating rates were used (1.6e07 and 5e07 BTU/Day). The boundary conditions used in the model correspond to the installation of a typical downhole pump in Orinoco Belt. Several parameters were analyzed such as pressures, temperatures, viscosities, production rate, gas-oil ratio, in order to determine the effect of the heating.

Based on this study, electric heating represents a good option for good sand quality reservoirs with low API gravity oils where a small change of temperature generates great change in viscosity. Special grid refinement must be performed within the wellbore in order to allow the simulator to accurately estimate the properties and conditions in this area where significant changes occur. Electric heating reduces the viscosity near wellbore and increases the bottom-hole pressure avoiding excessive gas liberation near the well. This creates favourable conditions for production delaying an oil relative permeability drop. Based on the simulations studied, this method increases the recovery factor up to 60% the one obtained in cold production for a typical extra heavy oil.

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