Near surface velocities at Ekofisk from Scholte and refracted wave analysis
Bibliographic record
Abstract
Summary Life of Field Seismic (LoFS) permanent seabed seismic system has been installed and operating at the Ekofisk field since 2008. High quality active source seismic and passive seismic data have been recorded in the field and effectively used for management of the reservoir and overburden. In this paper we demonstrate how horizontally propagating surface waves from active source seismic data allow us to estimate near surface seismic velocities and associated anisotropy. We also show how the observed time dependent velocity changes are empirically associated with strain and stress changes from production induced subsidence. We base our analysis on Scholte waves, which are dispersive surface waves that propagate horizontally under the seabed, and critically refracted compressional (CRC) waves, which are P-waves that propagate horizontally along the seabed starting with the critical offset. The results indicate that the average seismic velocity is related to the expected principal stress magnitude, and seismic anisotropy is related to stress change preferential directions
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".