A Guide to High Pressure Air Injection (HPAI) Based Oil Recovery

Abstract

In recent years, high pressure air injection (HPAI) has proven to be a valuable IOR process, especially in deep, high pressure, low permeability fields where other recovery processes are uneconomic. This paper will provide engineers and engineering managers with a wide-ranging look at the key factors that should be addressed when considering a high pressure air injection (HPAI) based IOR process in a light oil reservoir. The paper is based on many years of involvement of the authors both in the laboratory and the field, as well as drawing on published literature. The main focus is on key design and operating criteria that must be considered, including reservoir screening, air injection design, ignition, and monitoring. The benefits and potential risks of HPAI are also discussed. Along with the discussion of design and operating criteria, the paper contributes significantly in the comparison of oxidation/combustion kinetics for light oils versus heavy oils (HPAI versus in situ combustion), as well as in a discussion of the oil mobilizing effects of a gas flood compared to an advancing thermal (combustion) front. Introduction In recent years, High Pressure Air Injection (HPAI) has received considerable attention as an effective IOR process, based primarily on the success of several projects located within the Williston Basin, and the vision and initiative by Amoco Production Company (now BP) in forming an industrial consortium to develop a state-of-the-art HPAI laboratory. This has led to increased interest from companies in exploring the suitability of the HPAI process for application in their onshore and offshore reservoir holdings. The intent of this paper is to provide managers as well as engineers with a reference that discusses several design and operational issues that are important to consider. It is based on the authors' nearly thirty years of research and consulting in the area of in situ combustion and HPAI. While the paper was not intended as a review of the large body of existing HPAI literature, there are several useful references that serve as a starting point for understanding the process. The papers by Erickson, et al.1 and Kumar, et al.2 provide good summaries of the HPAI projects that were started by Koch Exploration Company in the Buffalo Red River Units and the Medicine Pole Hills Unit located in the Williston Basin; these projects continue to be operated, currently by Continental Resources, Inc. Watts, et al.3 describe a newer project started in the nearby Horse Creek Field by Total Minatome Corporation, and a paper by Fassihi, et al.4 discusses the light oil air injection process and addresses various recovery mechanisms based on field and laboratory data. Fassihi, et al.5 discuss the economics associated with two separate air injection projects at West Hackberry, Louisana, and the Medicine Pole Hills Unit, N. Dakota. Moore, et al.6,7 describe strategies for design and operation of successful air injection-based processes, and highlight the significant differences between air injection in light and heavy oil reservoirs. Yannimaras and Tiffin8 and Tiffin and Yannimaras9 describe laboratory testing of the HPAI process at the Amoco Production Company laboratory using the combustion tube and the accelerating rate calorimeter, while Greaves, et al.10 describe light oil recovery by air injection, based on laboratory work at the University of Bath, U.K. Field-specific numerical simulations of the HPAI process have been described by Kumar11, Glandt, et al.12, and Kuhlman13. Finally, two classical air injection design papers by Nelson and McNeil14 and Gates and Ramey15 are important reading for anyone involved in the design of air injection-based IOR processes. As stated previously, this list does not represent the complete literature on HPAI, but represents an excellent starting point in learning about the process.

Recovery Factors in High-Pressure Air Injection Projects Revisited

“…During the combustion process between oxygen and oil, two possible reaction pathways exist: the first are referred to as "bondscission" reactions, and the second are called "oxygen-addition" reactions (Moore et al 2002). During bond-scission reactions, the oxygen reacts with the hydrocarbon molecules to principally produce carbon dioxide, water, and energy; in other words, these are traditional complete-combustion reactions.…”

“…Fortunately, for many high-pressure light oils, bond-scission reactions are the favored reaction path, and airinjection processes tend to operate there quite readily under a wide range of operating conditions (Moore et al 2002).…”

“…The subsequent impact of the oil displaced directly by the combustion zone will depend on the effectiveness of the generated flue gas on oil displacement from outside the thermal region. If oil displacement from the regions not directly affected by the thermal zone is high, the air/oil ratios (AORs) associated with the displacement of oil by the combustion zone will be so high that air injection to that portion of the reservoir will be stopped long before the combustion has advanced any appreciable distance within the reservoir (Moore et al 2002).…”

Enhanced Oil Recovery: An Update Review

“…The success and expansion of Buffalo and Medicine Pole Hill in North and South Dakota have contributed with the increase of HPAI projects in the area. Although all HPAI reported by Moritis [18] in Montana, North and South Dakota have been developed in the same low permeable dolomitic formation (Red River A, B and/or C), air injection have proven to have high potential to improve oil recovery and revitalize both mature and waterflooded carbonate reservoirs [190,191]. This will be especially true in fields located in remote locations with no access to CO 2 sources.…”

Technical Challenges for Offshore Heavy Oil Field Developments

“…Screening criteria for air injection projects and some recent successes in deeper reservoirs have been documented. 13 Problems with air injection processes include additional corrosion concerns, damage to or loss of wells to combustion front breakthrough, or erosion from high velocity gases. Tight emulsions and excessive oxygen requirements resulting from the high levels of coke deposition of heavy oils can also occur.…”