Quantitative Analysis of Mechanisms for Water-Related Sand Production
Bibliographic record
Abstract
Abstract It is well known that saturation changes of the rock-wetting phase or alterations in wetness can lead to sand instability, therefore sand production. Several possible mechanisms are discussed in the paper, among which chemical reactions between water and sand and the changes of capillary force as a part of cohesive strength are focused upon quantitatively. Based on the time frame of sand production record, four major possible chemical reactions between reservoir sand and formation water are identified and analyzed, including quartz hydrolysis, carbonate dissolution, ferruginous deposits and clay swelling. Those reactions increase sand instability either through altering the surface energy of the sand and physically changing the shape and size of cement, (known as Rebinder effect), or locally increasing the pressure gradient. The possibility to quantify the effects of those reactions is discussed and the main difficulties are pointed out. Resorting to an analytical model at the grain scale, which accounts for meniscus behavior and properties in two-phase liquid systems and expresses the results in terms of capillary bond force and a tensile strength in a Mohr-Coulomb plot, the manner and magnitude of the capillary force influence on sand stability after water breakthrough are quantitatively described. It is found that, at grain scale level, the capillary cohesive force is one to three orders higher than the destabilizing seepage force from fluid pressure gradient, depending on particle sizes. Therefore it should not be neglected in the analysis of sand instability. Furthermore surface tension of fluids is found to be linearly related to capillary bond force and therefore to rock strength (tensile strength or UCS), the magnitude of which highly depends on the sand particle size, especially when particles are small. The model is able to successfully explain many reported phenomena about both capillary force and water-related sand production. As a conclusion, changes of capillary force with water saturation may have more influence on sand failure than chemical reactions in weakly consolidated sandstone at the beginning of water breakthrough. After some critical water saturation, the capillary strength diminishes and chemical reactions may become dominant over time.
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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) | 0.001 | 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 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".