Experimental Analysis of CO2-Sequestration Efficiency During Oil Recovery in Naturally Fractured Reservoirs
Bibliographic record
Abstract
Abstract With urgent need of greenhouse gas sequestration and booming oil prices, underground oil/gas reservoirs seems the only value added choice. A great portion of current CO2 injection projects in the world is in naturally fractured reservoir. The matrix part of these reservoirs constitutes the major oil storage unit and this oil is targeted during CO2 injection. It is our intention to show that this media could also be used as permanent CO2 storage unit while recovering oil in it. These reservoirs, however, are complex in nature and the physics of the matrix-fracture interaction process during CO2 injection is still not known to great extend. To ease the complex nature of the problems, experiments were performed on artificially fractured (single) Berea sandstone cores saturated with n-decane. CO2 was injected at constant rates into the fracture while maintaining the high pressure into the core and the system. Injection and production data were monitored and collected using continuous data logging system. After continuous injection diffusion of CO2 was allowed to occur by shutting down the system for a specific period of time and then following a blowdown period to produce oil recovered by diffusion from matrix to fracture. At different pressure steps, produced liquid was analyzed using gas chromatography while the produced gas measured using continuous flow meter. The CO2 storage capacity of the rock with change in the pressure and the amount of oil recovered during blow down period was analyzed. The results of the continuous injection experiments were used to obtain diffusion coefficients by matching the simulation results. Using dimensionless analysis and matrix-fracture diffusion groups, a critical number for optimal recovery/sequestration was obtained. The pressure decay behavior during the shutdown was analyzed in conjunction with the gas chromatograph analysis of produced oil sample collected during blowdown after the quasi-equilibrium reached during pressure decay. This led to insights into the governing mechanism of extraction/condensation and miscibility for recovering lighter to heavier hydrocarbons during pressure depletion from fractured reservoirs.
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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 | 0.000 | 0.001 |
| 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) | 0.001 | 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 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".