Chalk Surface Area Evolution during Flow of Reactive Brines: Does Oil Play a Role?
Bibliographic record
Abstract
Prolonged injection of magnesium chloride (MgCl 2 ) brine into water-wet chalk cores leads to dissolution of calcite and precipitation of magnesium-bearing minerals. In low permeable and highly porous chalk, the mineral surfaces dominate multiphase flow properties. The hydrophobic/hydrophilic behavior of these mineral surfaces is subject to changes when aged in oil at high temperature over time, and from mineral dissolution and precipitation processes. In this study, we evaluate to which extent chemical interactions induced by the continuous MgCl 2 brine injection modify the water wetness of chalk samples saturated by oil/water mixtures and compare the evolving results to a 100% water-saturated parallel reference test. The potential of MgCl 2 brine to improve the oil recovery after the freely movable hydrocarbons are produced is also assessed. In situ wettability measurements were carried out during the injection program using chromatographic separation, where the delay in the increase of effluent concentration of the adsorbing sulfate ion was compared to a nonaffine tracer. These measurements were performed every 10 days to estimate the evolution in mineral surface area in contact with water. The results show an increased delay time for the sulfate ion, linked to an increase of the mineral surface area. This is observed in both water-wet and mixed-wet cores, but is found to be more dominating in the mixed-wet samples. This implied that oil, which was adsorbed on the mineral surfaces, got mobilized in addition to an increased overall specific surface area as new magnesium-bearing minerals precipitated and grew during the MgCl 2 brine flow. This is supported by continuous effluent analysis displaying a reduced magnesium and increased calcium concentration. Petrophysical analysis of cores before and after flow displayed trends along the axis of the sample. Changes in density and specific surface area were more dominant on the inlet side than the outlet side. Even though magnesium (Mg 2+ ) ions in the injection brine increased the available water-wet area in the samples, the nonequilibrium chemical reactions did not lead to additional oil recovery.
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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".