Challenges and Risk Management Strategy for Enhanced Oil Recovery Projects in Carbonate Reservoirs of a Giant Field in Middle East

摘要

Late Cretaceous – Early Tertiary carbonate reservoirs of the giant Wafra Field, located in the Kuwait - Saudi Arabia Divided Zone, hold huge resource of heavy oil in 3 reservoirs, namely 1st Eocene, 2nd Eocene, and Maastrichtian. More than 50 years of primary production from these high porosity, moderate permeability carbonates has recovered less than 5% of this volume and the ultimate recovery is not expected to exceed 10%. Low primary recovery is attributed to oil gravity, viscosity and drive mechanism. Suitable EOR technology is needed to unlock these huge resources. In absence of any commercial analogs, application of EOR technology carries enormous risks in terms of technical viability, reserves recovery and resources commitment. Proper understanding of the reservoir and optimization of EOR technology are essential to mitigate these risks to a manageable level. This paper will discuss the process used to meet various challenges and mitigate risks of EOR application in 1st and 2nd Eocene reservoirs through exhaustive screening studies, pilot projects and testing innovative technologies. Detailed screening study suggested the suitability of steamflood for 1st Eocene and both waterflood and steamflood for the deeper 2nd Eocene reservoir. Both projects have serious challenges due to reservoir nature, uncertainty in reservoir characterization, non-availability of fresh water, lack of proven technology for processing produced water for steam generation, disposal of excess produced water, fuel for steam generation, and safe environment for workers, public and wild life. These challenges make the EOR projects very high risk ventures. These risks are being managed through extensive G&G and simulation studies, exhaustive screening work and properly designed pilot projects. Five pilot projects are under implementation to resolve the number of uncertainties and manage associated risks in the high reward EOR process for these reservoirs. This paper will share the strategy, work flow, uncertainty management and risk mitigation plan for these pilot projects and innovative technology being tested to manage challenges in full field application of EOR in carbonate reservoirs. Sharing of processes and innovative technology with industry will lead to success in mitigation of risks in EOR projects in carbonate reservoirs.