A Review of Conventionally Undrillable Wells with Ultra-Narrow Pressure Windows Successfully Drilled Utilizing MPD Over the Last Five Years in USA and Canada
Bibliographic record
Abstract
Abstract Managed Pressure Drilling (MPD) has been used on multiple projects by several operators in different regions of North America to drill through formations that had ultra-narrow (or conventionally undrillable) pressure windows. As illustrated by the case studies discussed here, a combination of Constant Bottomhole Pressure (CBHP) MPD, Anchor Point MPD, and Pressurized MudCap Drilling (PMCD) MPD variations helped drill through several of these formations, trip in and out safely, log and core hole-sections, and run liner or casing to the target depth and cement it in place. Thus, MPD successfully enabled the operators to tap into these otherwise unattainable reserves. Typical challenges include formation/wellbore instability, shallow-water flows, over-pressured formations, low FIT/LOT, fracture pressure/wellbore strength regression, and moderate to severe losses. A few anomalous formations with uncertain pressure regimes resulted in severe to total losses on one well, while an adjacent well drilled at similar depths resulted in high-pressure influxes with ensuing well-control consequences. A detailed evaluation of historical data, comprehensive hydraulic analysis, appropriate MPD design and planning, and use of technologically advanced, reliable, efficient, and well-maintained equipment were critical factors that led to the success of these MPD projects. Above all, utilizing knowledgeable, experienced, and well-trained MPD personnel helped integrate MPD with the existing rig systems and teams and consistently solve the seemingly insurmountable drilling challenges safely and reliably.
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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 | 0.004 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.017 | 0.029 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".