Vertical Seismic Profiles through Gas-Hydrate-Bearing Sediments
Bibliographic record
Abstract
Vertical seismic profiles (VSPs) are commonly used for linking borehole information with surface-seismic surveys. Since Ocean Drilling Program (ODP) Leg 146 offshore Cascadia, VSP surveys have been conducted in all major gas-hydrate drilling campaigns, both offshore and onshore. We have compiled results from VSPs during ODP Legs 146 (1993, Cascadia margin), 164 (1995, Blake Ridge), 204 (2002, Hydrate Ridge), the onshore Mallik campaigns in 1998 and 2002, as well as the Nankai Trough exploratory wells. We also give a brief overview of other recent VSP operations conducted to investigate gas hydrates. All of these campaigns included zero-offset VSPs, including a shear-wave VSP at the Mallik sites. Zero-offset VSPs proved invaluable for tying seismic surveys to borehole data and also for interpolating data gaps in sonic logs. Compressional-to-shear conversion was observed in both constant-offset and walkaway VSPs allowing measurement of shear-wave velocity offshore. Seismic anisotropy determined from walkaway VSPs indicated a preferential alignment of clay platelets within the Blake Ridge and gas-hydrate-bearing veins on Hydrate Ridge. Finally, a unique approach, resonance scattering, emerges as a promising tool to quantify the lateral heterogeneity of gas-hydrate deposits. Some challenges still remain for VSP operations in gas-hydrate-bearing sediments, particularly offshore due to the proximity of gas hydrates to the seafloor. Conventional VSPs have now matured to be a standard tool for gas-hydrate wells. The recent rapid developments of VSP technology, both on the acquisition and evaluation side, enable us to make new and exciting insights into natural gas hydrates.
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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 | 0.001 | 0.001 |
| 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) | 0.002 | 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".