Is High-Pressure Air Injection (HPAI) Simply a Flue-Gas Flood?
Bibliographic record
Abstract
Abstract High-Pressure Air Injection (HPAI) is an 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 as a simple fluegas 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 repressurization 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 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 are definitely not behaving 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 on 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 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 combustion front will depend on the effectiveness of the generated flue gas on oil displacement from outside the thermal region. For many years, there has been some discussion regarding the effective driving mechanisms associated with the HPAI process; some authors have assumed it is essentially attributable to the in-situ generated flue gas displacement and consequently the process is analogous to a flue-gas injection, while others recognize the thermal nature of the process. Clara et al.11, explained the air injection technique applied to light-oil reservoirs, and proposed a laboratory strategy for evaluation of an air injection project. It was stated that regardless of the oxidation zones, the air injection process in a light oil reservoir is comparable to a flue-gas injection process. Hunedi et al.12, presented results of an exhaustive EOR screening based on successful field trials and physics of the oil recovery mechanisms for each method; with the possibility to be applied in eight oil fields (30.2 to 41.3 ° API) in the Euphrates Graben.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".