Characterization of Weakly Cemented Sands from Geophysical Logs
Bibliographic record
Abstract
Shear strength is a critical parameter in evaluating the sanding potential of weakly cemented sands in oil-bearing formations. The current state-of-the-practice is to use empirical correlations (e.g., relating unconfined compressive strength to velocity logs) developed almost entirely for high-strength rocks that grossly overestimate the strength of weakly cemented sands. The objective of this study was to develop a methodology for estimating the strength of weakly cemented sands from commonly measured geophysical logs. An extensive laboratory testing program was first performed on a simulated weakly cemented sand from an oil well. An empirical model was developed that links porosity, horizontal effective stress, and the stresses at failure to synthetic compressional and shear wave velocities calculated using a modified Biot-Gassmann theory. A procedure was then established to infer unconfined compressive strength (qu), real cohesion (c'r) and tangential friction angle (j't) from the estimated stresses at failure. The model and the procedure were then applied to wireline log data from an oil-bearing formation, and there was reasonable agreement between estimated and measured values of strength. This methodology has the potential to estimate strength parameters of weakly cemented oil bearing sand directly from density/porosity logs and compression wave velocity logs.
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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) | 0.000 | 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 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".