Feasibility of using electrical downhole heaters in Faja heavy oil reservoirs

Abstract

Abstract The Orinoco Belt (Faja) in Venezuela contains one of the largest resources of heavy and extra-heavy oil in the world. Due to the production decline of conventional light crude, projects must focus on increasing the recovery of heavy and extra-heavy oils using thermal and non-thermal methods. Steam-based thermal recovery processes are more efficient in low pressure reservoirs; however due to their depth, the initial pressures of the reservoirs in the Faja are relatively high, in the range of 600 to 1,500 psi with viscosities typically greater than 2,000 cp. For the above reasons, it is important to decrease the pressure of the reservoirs with primary production techniques to facilitate the economical implementation of steam injection based methods. The initial production of heavy and viscous oils can be accelerated by the adequate use of downhole heaters that, by providing energy to the vicinity of the well, decrease oil viscosity and increase the oil production rate. A consequential advantage of using downhole heaters as a preamble to a steam injection process is that they accelerate early production and reservoir pressure decline while the equipment associated with steam injection, including steam boilers, insulated pipes and proper facilities are designed, ordered, installed and commissioned. This paper analyzes the effects of downhole heaters as a stimulation method through the use of a numerical model of a representative field in the Ayacucho area of the Orinoco Oil Belt. The study has been divided in three parts. The first part relates to the use of downhole heaters in thick sands, stimulating both vertical and horizontal wells in the reservoir. The second one evaluates the temporary application of downhole heaters in horizontal wells for a limited period of time to accelerate production and pressure decline, followed by a full implementation of a Steam Assisted Gravity Drainage (SAGD) process. The third part of the paper covers basic economical analyses perfor ed using estimated capital and operating expenses with oil production curves from each case, to assist in the comparison of their worth using common economic parameters. Introduction Heavy oil reservoirs are increasingly being developed because of their great potential, the necessity to compensate for the decline of conventional oil production and by the favorable opportunities created by current high oil prices that make these kinds of projects more profitable. Countries like Canada, Russia, and Venezuela are directing their efforts to develop this kind of unconventional oil reservoirs. The technology to produce heavy and extra-heavy oil is still under accelerated development to meet the challenges to efficiently produce and procure the proper facilities for thermal operations.