Experimental and modeling assessment of CO2 EOR and storage performances in tight oil reservoir, Yanchang oilfield, China
Why this work is in the frame
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Bibliographic record
Abstract
Previous experimental studies have shown that CO 2 injections can significantly enhance oil recovery in tight oil reservoirs and sequestrate CO 2 permanently. However, performance varies in places when the technologies are scaled up in field pilot tests. Therefore, investigating CO 2 EOR (Enhanced Oil Recovery) and storage mechanisms during CO 2 injection in field-scale tight sandstone reservoirs is crucial. In this study, laboratory Pressure-Volume-Texperature (PVT) tests and field pilot tests of CO 2 injection in a tight oil reservoir of the Yanchang oilfield in the Ordos Basin were analyzed. Reservoir simulations of CO 2 injections, including continuous and water alternative gas injections, are conducted after history matching. Laboratory PVT results show that oil viscosity decreases from 5.10 to 2.38 mPa·s as pressure reduces from initial formation conditions to atmospheric pressure, and swells oil to 1.50 times at a saturation pressure of 240.0 bar, which is larger than the minimum miscible pressure of 178.0 bar from the slim tube test. Reservoir simulation results of continuous and WAG injection scenarios show that oil production increases with CO 2 injection rate, and oil recovery increments are 21.6 % and 19.3 %, respectively, for Case 3 and Case 5. This is because reservoir pressure increases with more injected CO 2 , resulting in higher displacement efficiency, and larger amounts of CO 2 can also lead to higher sweep efficiency in the lateral directions. However, CO 2 EOR efficiency decreases gradually after the CO 2 breakthrough. In addition, CO 2 migration in the lateral direction relates to the CO 2 injection rate. The areas of dissolved CO 2 are larger than those of gaseous CO 2, especially for WAG cases, while both increase with CO 2 injection rate due to a larger pressure gradient. The amount of CO 2 through structural trapping for the continuous injection cases is higher than solubility trapping, followed by residual trapping. Differently, the amounts of gaseous CO 2 are close to those of the dissolved CO 2 for the WAG cases due to water injection. The findings in this study are significant for understanding and demonstrating the CO 2 EOR, storage mechanisms in lab and field scales, and provide a valuable reference for scaling up the technologies in tight oil reservoirs.
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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 it