Recent Developments and Remaining Challenges of Enhanced Oil Recovery

Abstract

R&D Grand Challenges - This is the second in a series of articles on the great challenges facing the oil and gas industry as outlined by the SPE R&D Committee. The R&D challenges comprise broad upstream business needs: increasing recovery factors, in-situ molecular manipulation, carbon capture and sequestration, produced water management, higher resolution subsurface imaging of hydrocarbons, and the environment. The articles in this series are examining each of these challenges in depth. The R&D Grand Challenges Series, comprising articles published in JPT during 2011 and 2012, is available as a collection on OnePetro (SPE-163061-JPT). The world is changing. Some look back and some look forward. Some look at the challenges of ramping up enhanced oil recovery (EOR) in the past and some look at the opportunities for doing so now. This article will provide a broad view of recent developments and the remaining challenges for readers who are not EOR specialists. There has been a renaissance in chemical EOR during the past few years because of major advances in the technology and high oil prices. Thermal and miscible gas methods are much more mature with the exception of processes such as co-injection of gases and surfactants for mobility control. The synergy between the EOR processes and improved reservoir characterization and formation evaluation, reservoir modeling and simulation, reservoir management, well technology, production methods, and facilities is significant and not as widely recognized as it should be. Polymer flooding is the simplest and most widely used chemical EOR process. Polymer flooding has been used commercially since the 1960s; more oil is produced by polymer flooding than all of the other chemical EOR processes combined. Adding polymer to the water increases its viscosity. The benefit of polymer flooding increases as the oil viscosity and/or the reservoir heterogeneity increases. Polyacrylamide copolymers or hydrolyzed polyacrylamide (HPAM) polymers are by far the most widely used polymer for EOR. Much higher molecular weight HPAM is now available than when it was first used in the 1960s and 1970s. The quality of commercial HPAM polymer has also improved dramatically and the price relative to crude oil has decreased. In the early 1970s, oil sold for about USD 3/bbl and HPAM polymer for about USD 1.50/lb. Now oil is about USD 100/bbl and HPAM stays about the same price. About 1 to 2 lbs of polymer are needed to produce an incremental barrel of oil, which means the polymer cost is about USD 1.50/bbl to USD 3/bbl. This helps explain why the number of polymer floods is increasing exponentially and about 1 billion lbs of polymer will be used for EOR this year. Most early polymer floods were done using very small amounts of polymer (i.e., low polymer concentrations and small pore volumes of polymer solution), but now we know polymer floods perform much better at large polymer concentration.