Landing with confidence and accuracy in a big bore subsea gas producer – an integrated approach for setting a critical casing point in the Jansz-Io field development
Bibliographic record
Abstract
As part of the Gorgon Stage 2 project, a total of four production wells were installed at a new manifold within the Jansz-Io gas field. A key well construction challenge was the placement of the 12 ¼″ section total depth (TD). Due to the presence of reservoir depletion, the mud weight required to drill the sandstone would be insufficient to prevent wellbore collapse in the Barrow Shale immediately above the reservoir. Hence, the casing design called to isolate the entire Barrow Shale interval by placing the 9 ⅝″ production liner shoe immediately inside the reservoir. To avoid damaging the high-quality sandstone in the upper reservoir, it was desired to limit the reservoir penetration to less than 1 m true vertical depth (TVD) at 80° inclination. Chevron recognised several challenges in landing the wells, which included: seismic uncertainty of the reservoir top, poor resistivity contrast and the lack of significant markers in the overburden. Conventional methods such as near-bit gamma ray carried high risk because the sensor offset to bit is close to the penetration limit. Therefore, a new approach of integrating a deep directional resistivity (DDR) tool and an at-bit resistivity measurement to make the casing point decision was proposed. With this new approach, all four wells were landed, with actual reservoir penetration less than 1 m TVD. The real-time data from the DDR tool allowed the operator to efficiently drill the section, only reducing the rate of penetration immediately prior to entering the reservoir. The at-bit resistivity tool, drilling parameter changes and cuttings identification were beneficial to confirm reservoir entry and call section TD.
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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 | 0.002 | 0.001 |
| 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 | 0.001 |
| 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".