Downhole Electrical Heating for Heavy Oil Enhanced Recovery: A Successful Application in Offshore Congo

The development of heavy oil reservoirs is one the future targets of the major oil companies worldwide. Most of the heavy oil fields are produced through cold production methods leaving behind significant amounts of unproduced reserves. Today several EOR (Enhanced Oil Recovery) techniques and, in particular, thermal methods are available to achieve higher recovery factors. However, some technologies, like the downhole electrical heating have been recently improved, allowing enhancement of production, therefore, improvement of the recovery factor with relatively low investment cost with respect to the high costs involved in the implementation of the thermal technologies. In order to increase the production of a heavy oil reservoir in the offshore Congo, a study of down hole electrical heating application have been carried out showing encouraging results. The aim of the study was to evaluate the benefit associated to the application of this technology through the reservoir modeling. Significant results were achieved in terms of increasing of the recovery factor. The use of heat to increase the reservoir temperature showed good results in terms of heavy oil viscosity reduction starting from 1,000 cP at reservoir conditions (34°C) down to much lower values throughout the production time resulting in increased production rate and consequently, higher recovery factor from this reservoir. The first application of this technology has been performed in a long horizontal well section of about 500 meters length completed with production sand screen. The electrical heating mineral insulated three phase cables were deployed throughout the horizontal well section by means of a dedicated completion tail pipe. Several design challenges have been faced to properly centralize the heating cables and clamp the same around the completion tail pipe due to the well design constraints. This paper will describe the results of the reservoir modelling analysis, the completion planning activities and the lessons learned during the operations.