Is High-Pressure Air Injection (HPAI) Simply a Flue-Gas Flood?

Abstract

High-pressure air injection (HPAI) is an enhanced oil recovery (EOR) process in which compressed air is injected into a deep, light-oil reservoir, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated temperature to produce carbon dioxide. Over the years, HPAI has been considered a simple flue-gas flood, giving little credit to the thermal drive as a production mechanism. The truth is that, although early production during a HPAI process is mainly due to re-pressurization and gasflood effects, once a pore volume of air has been injected the combustion front becomes the main driving mechanism. This paper presents laboratory and field evidence of the presence of a thermal front during HPAI operations, and of its beneficial impact on oil production. Production and injection data from the Buffalo Field, which comprises the oldest HPAI projects currently in operation, were gathered and analyzed for this purpose. These HPAI projects definitely do not behave as simple immiscible gasfloods. This study shows that a HPAI project has the potential to yield higher recoveries than a simple immiscible gasflood. Furthermore, it gives recommendations about how to operate the process to take advantage of its full capabilities. Introduction High-Pressure Air Injection (HPAI) is an emerging technology for the enhanced oil recovery (EOR) of light oils that has proven to be a valuable process, especially in deep, thin, low-permeability reservoirs(1-7). A number of successful high-pressure air injection projects in light oil reservoirs have been documented in the literature(8-10). Most of these projects have been operating for many years, attesting to their technical and economic success. The improvement in recovery of light oil by HPAI involves a combination of complex processes, each contributing to the overall recovery. These processes include flue gas sweeping, field re-pressurization, oil swelling, viscosity reduction, stripping of the lighter components of the oil, and thermal effects. Early production during the HPAI process is related to re-pressurization and gasflood effects; hence, the influence of the thermal zone is secondary during the early life of an injector. The oil displaced directly by the thermal front will depend on the effectiveness of the generated flue gas on oil displacement from outside the thermal region.

Using DSC/TG/DTA techniques to re-evaluate the effect of clays on crude oil oxidation kinetics

“…At 200°C, bond scission begins to predominate in LTO reaction to form the carbon dioxide and water, which leads to the decreasing diversity of oil mass loss in air and nitrogen flow. As a result, the total mass loss of oil in presence of air is greater than that of nitrogen during the period of temperature reaching to 360°C Montes et al(2010). pointed out that oxygen addition reaction usually occurred at about 150°C below while the bond scission occurred in 250-300°C,which was close to the experimental results of this paper.…”

Potential for In Situ Combustion in Depleted Conventional Oil Reservoirs

“…Laboratory combustion tube tests indicate that the thermal front is an important displacement mechanism for light oils. As described by Montes (2010), fluid recovery (oil plus water) is almost in direct proportion to the volume burned. This behavior was implied by Erickson (1994) in his landmark paper introducing the air injection process in the Williston Basin.…”

Characterizing the Fuel Deposition Process of Crude Oil Oxidation in Air Injection

“…Simultaneously, the content of the CO 2 in the effluent gas reached up to approximately 15 %. According to Montes et al, 33 a CO 2 level of exceeding 12% indicated that combustion-like reactions occurred. The above-mentioned data implied that the combustion reaction was dominated for the further oxidation of the formed coke.…”