Life of Well Isolation Implemented in Major North Sea Development
Bibliographic record
Abstract
Abstract The Buzzard field operated by Nexen is the largest oil discovery in the North Sea since the early 1990s. About 27 production wells, of approximately 9,000 ft total vertical depth (TVD), will be drilled during the field life. Maximized life of well isolation is imperative. The production liners are being cemented with a life-of-well engineered solution. The reservoir section consists of two discrete oil-bearing sandstones. Oil recovery will be maximized by water injection from subsea wells. Isolation of the production sands enhance management of the waterflood and thus maximize the producible volume. The challenge was to develop a cement system that could achieve and maintain isolation throughout the life of the field. A finite element-based analysis tool was used to build a model of the reservoir section. The model was then used to predict the forces on the cement sheath throughout its life under all load conditions, including those caused by pressure and thermal changes during drilling, completion, and sustained production. The model predicted that a conventional cement sheath could fail in three modes: debonding at the formation, compressive shear, and radial cracking. A cement sheath with lower Young's modulus, higher tensile strength, and shrinkage compensation was required. A series of designs were tested to select the optimum solution that met the life-of-well needs. The successful implementation of this new approach to cementing required special planning and organization. To date, 13 wells have been cemented with the life-of-well solution, with no operational problems and indication of good placement. Bond-log results differ from those expected from conventional slurries because of elastic components in the life-of-well slurry. Special data processing techniques have been developed to allow evaluation using conventional bond logs; these are presented in this paper. Analysis, design, and field implementation discussed in this paper can be applied to field development in other locations where zonal isolation during the well life is critical.
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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".