Performance of CO2 Huff-and-Puff Process in Fractured Media (Experimental Results)
Bibliographic record
Abstract
Abstract In this study, the performance and efficiency of CO2 huffand-puff process for improving oil recovery and subsequent storage of CO2 in fractured porous media is examined and the results of experimental tests are presented. The experimental set up consisted of a high-pressure stainless steel cell made specially to hold a cylindrical core with spacing around it to simulate fractures surrounding matrix. The matrix was saturated with normal decane, which was used as oil during these experiments. Total six sets of huff-and-puff experiments, using CO2 as solvent, were conducted for pressures of 250, 500, 750, 1000, 1250, and 1500 psi. Each set of the huff-and-puff experiments were conducted by injecting CO2 in fracture system surrounding the core (injection step). Then, the system was shut-in for a period of 24 hours to allow CO2 to diffuse from fracture into the oil in matrix (soaking period step). At the end of soaking period, the pressure was released and the oil production was measured (production step). The above cycle was repeated until no more oil was produced. The results obtained show that CO2 huff-and-puff process improves the oil production from fractured reservoirs, significantly. These results also indicate that the oil recovery is higher for huff-andpuff experiments conducted at higher pressures. Introduction Implementing huff-and-puff processes, through utilizing various miscible and immiscible solvents, for improving oil recovery from oil reservoirs has been tested by various researchers through laboratory investigations, as well as field tests. Most of the works reported, either in the laboratory or field trials, are limited to the conventional single porosity reservoirs. Cyclic CO2 injection was originally proposed as an alternative to cyclic steam stimulation for heavy oil reservoirs. However, it has found wide applications in light-oil reservoirs (1). An immiscible CO2 huff-and-puff pilot project was carried out by Turkish Petroleum Corporation in Camurla Field that has a heavy crude oil of 11–12 °API (2). The laboratory tests, reservoir studies, and design of injection and production facilities were done by IFP (Institute Fran?ois du Petrole). The results of this early application of huff-and-puff immiscible CO2 project were not economical in all stages due to the lack of equipments and some field problems. However, significant reduction in the oil viscosity and interfacial tension resulted in improving oil recovery in some stages of this project. Also, there was an evidence of dissolution of calcium carbonate by carbonic acid which resulted in improving permeability. Another study by Monger and Coma showed that waterflood residual oil can be displaced by CO2 huff-and-puff process in a light crude oil Berea core (3). They also pointed out that, there is less sensitivity to the soak period, and operating at the minimum miscibility pressure (MMP) is not critical to the ultimate recovery. Later on, an evaluation of CO2 huff-and-puff tests on 28 wells in Texas by Haskin and Alston confirmed that soak time period has not significant impact on the oil recovery under immiscible condition (4).
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| 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".