Vacuum Insulated Tubing Efficiency for Offshore Steam Injection: Case Study from Emeraude Field Congo

Abstract This paper validates the thermal efficiency of Vacuum Insulated Tubing (VIT) for offshore steam injection application on Emeraude Field (Congo). It includes field measurement of thermal dissipation prior to VIT installation, steam injection logging tool interpretation, thermal losses modelling of offshore steam injection, and well monitoring data post-installation. It is concluded that VIT improved steam quality from 35% up to +95%, leading to significant steam generation cost savings and overall EOR efficiency improvement. PERENCO/CONGOREP started offshore steam injection in Emeraude in April 2010 from the new MOAB platform, with 4 steam injector and 9 producer wells. The purpose of the project was to pilot offshore steam injection, using an inverted 5 spot pattern on the R2 reservoir. In 2013, steam PLT runs and temperature monitoring measured that steam quality downhole was only 35%, meaning that 65% of latent heat was lost by thermal conduction and sea water convection along conductor pipe. Following these observations, thermal model simulation was performed, which confirmed the severity of thermal losses along the submerged casing section (60m water depth at MOAB location). Moreover, shallow water bearing reservoirs were showing temperature increases in neighboring production wells, revealing unexpected sub-surface thermal losses. A remedial option was identified as the implementation of vacuum insulated tubing on steam injectors. PERENCO and MAJUS collaborated to take advantage of a workover opportunity in July 2015, and fast-tracked VIT installation using 3″1/2 ID VIT tubings down to 308m. Steam injection was resumed immediately, and we observed a positive insulation effect in neighboring wells. With only 0.8t/hour steam injection, EMM-511 well demonstrated the same thermal impact as a 2t/hour non-insulated injector. Steam savings allowed the boiler to be run on fuel gas only, reducing the need for extra fuel oil consumption. From September 2015, decreased water cuts were also noticed in neighboring production wells, unlocking an additional bottleneck. New steam PLT runs have not been made yet, but these indirect observations confirmed thermal loss predictions of +95% steam efficiency with VIT as predicted by thermal modelling. CONGOREP will continue to adapt Thermal EOR strategy to respond to offshore conditions. By implementing MAJUS vacuum insulated tubings on the EMM-511 well, we demonstrated the fundamental impact of thermal insulation in offshore environment. By increasing steam quality up to +90%, we significantly reduced fuel oil consumption, improved thermal efficiency, and reduced water breakthrough on producing wells. VIT technology has been field proven for offshore steam injection with increasing steam efficiency and overall thermal efficiency. Thermal simulation predictions were validated by field monitoring and positive impact was demonstrated on neighbouring wells.