Performance of Air Injection vs. CO2/Water Injection in a Tight, Light-Oil Reservoir: A Laboratory Study
Bibliographic record
Abstract
Summary This paper outlines the results of an early-stage comparative study of air-injection-based and immiscible-carbon-dioxide (CO2)/water-injection-based enhanced-oil-recovery (EOR) processes for a 30+ °API tight, light-oil reservoir. This was accomplished by embedding multiple low-permeability core plugs in crushed reservoir-core material to create a composite core that was contained in a 1.84-m-long core holder. The objectives of this unscaled experimental work were to understand the suitability of each EOR process for a low-permeability reservoir; to define process parameters before a potential field pilot; and to understand the relative merits of each EOR process to mobilize light oil from a tight matrix to a fracture network. A detailed experimental investigation was conducted at realistic reservoir conditions to evaluate the feasibility of an air-injection-based EOR process. The air-injection results were compared with those from an immiscible CO2/water-injection EOR experiment using the same experimental setup and reservoir conditions. Both the air- and CO2/water-coreflood tests were performed at 10 340 kPag (1,500 psig) and 99°C in a 100-mm diameter, 1.84-m-long composite-core holder using 38-mm-diameter reservoir core plugs (that represented the matrix) mounted within the crushed reservoir-core material (that represented the fracture); inert helium gas was used to pressure up the core holder to reservoir pressure. Permeability of the core plugs was from 0.3 to 3 md, while the permeability of the crushed core material was 1 to 3 darcies. Air injection was performed as a standard, one-dimensional combustion-tube test with injection of 2.3 pore volumes (PVs) of air to burn 71% of the packed core length (including helium, a total of 4.3 PV of gas injected). The CO2/water coreflood was performed with the injection of 2.86 PV of CO2 followed by an extended soak period, then a second injection of an additional 2.86 PV of CO2, followed by the injection of 2.6 PV of water. The pretest and post-test core-plug measurements of oil saturation show that the air-injection process removed significantly larger quantities of hydrocarbons than the immiscible-CO2/water-injection process. Relative to the initial conditions of the core plugs for the air-injection experiment, more than 95% of the hydrocarbons were removed (note that some fraction of original oil was consumed as fuel). In the post-test CO2/water-injection core plugs, oil recovery was in the range of 30 to 55% of initial oil in place (IOIP). These findings suggest that, under an appropriate field design, both processes have the potential to recover incremental oil from tight reservoirs. However, the air-injection process might be better suited to mobilize oil, because of thermal expansion, than the CO2/waterflood process.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".