Successful Installations and Predictable Performance of Solid Expandable Drilling Liner in Greater Ekofisk Field, Offshore North Sea
Bibliographic record
Abstract
Abstract Drilling the lower overburden section in specific parts of the Greater Ekofisk Area (GEA) fields can be very troublesome. Wells in these parts may intersect shales with high gas content in the upper section (requiring high mud weight) and unstable zones with massive lost circulation risk (requiring low mud weight) near the base of the interval. These challenges have raised the need for a contingency drilling liner to "split" the section in two parts. Rather than changing the basic well design, the operator fronted the development of an 8-5/8″ expandable drilling liner with high collapse resistance for this purpose. This string provides 8.514″ post-expansion drift ID that accommodate an 8 ½″ bit size for the reservoir section, which is critical for GEA well design strategy. In the past five years, the operator has successfully installed 31 800 ft of 8-5/8″ expandable liner in 27 different wellbores with near perfect track record. The average liner length installed is 1 140 ft per wellbore, with an average installation time of 2.8 rig days. The solid expandable tubular (SET) drilling liner has been utilized both as part of the planned well design and as contingency liner. It has, on occasions, been worked down with parameters outside the stated specifications and still been successfully expanded afterwards. The 8-5/8″ expandable liner is now a proven system and has been one of the key enablers to achieve well objectives by maintaining hole size in a predictable manner. It provides a better drilling window for reservoir drilling and reservoir liner cementing compared to a conventional 7-3/4″ liner alternative. It also enables further contingency solutions in case other difficulties arise in the reservoir section. This technical paper describes how the operator in the overcame a significant geological challenge by working with an expandable pipe supplier to develop a unique size and strength of expandable liner that fits with the base case GEA well design. The paper also reviews the installation experiences, associated risks, performance, and key learnings with expandable liners.
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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".