Experimental Investigation of Shale Wettability and Its Alteration Mechanisms in Supercritical CO<sub>2</sub>–Brine–Oil Systems: Implications for CO<sub>2</sub> Storage and Enhanced Oil Recovery
Bibliographic record
Abstract
Abstract CO2 is highly effective at enhancing shale oil recovery while facilitating geological sequestration. The interaction between supercritical CO2 (ScCO2) and shale significantly alters the wettability, a key factor influencing both the oil recovery efficiency and the CO2 storage capacity. A novel investigation was carried out to explore the dynamic characteristics of the CO2–brine–oil–shale multiphase system and the mechanisms underlying wettability alteration using samples from the Yanchang shale formation in China. The wettability of shale samples was characterized by high-temperature and high-pressure contact angle tests, while quantitative analysis of the mineral composition was conducted through ScCO2-shale reaction experiments combined with XRD. FTIR and zeta potential tests determined the types and amounts of surface charged groups, and 3D surface morphology scanning reflected structural changes. Results showed that ScCO2 injection significantly weakened the water-wetness of shale. Temperature and pressure were key external factors: increasing temperature shifted the wettability from water-wet toward neutral-wet, while higher pressure drove it closer to oil-wet. After ScCO2 treatment, significant alterations in the physicochemical properties of shale were observed, which fundamentally influenced its wettability. The content of clay minerals, encompassing both hydrophilic and hydrophobic phases, was reduced, whereas the proportion of hydrophilic quartz increased. The decrease in hydrophilic hydroxyl groups (OH), increase in oleophilic oxygen-containing groups (C–O–C), and reduction in the zeta potential collectively altered the multiphase interfacial forces, thereby impacting the spreading behavior of liquids on shale surfaces. ScCO2 also increased shale surface roughness at the nanoscale, which can alter fluid distribution by providing additional adsorption sites and modifying the spreading behavior of fluids. These findings provide theoretical support for artificial wettability regulation, aiding shale oil recovery and CO2 storage.
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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 | 0.000 |
| 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) | 0.001 | 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".