Reducing Cost and Risk with Cemented-Back Monobore Well Construction in the Cardium Formation
Bibliographic record
Abstract
Abstract Operators in the Cardium formation of central Alberta are increasingly adopting a cemented-back monobore well design to reduce costs and improve operational efficiency. Extensive field data from more than 360 wells completed by an operator working in this formation demonstrates the operational advantages and substantial cost savings gained by adopting a monobore well design. This paper details the evolution of well construction for open hole horizontals in the Cardium, and provides cost and operational comparisons between drilling different wellbore sizes, running different casing sizes, and using different stage tools to cement from the heel of the well back to surface. The operator completed 77 wells in the Cardium using 177.8 mm intermediate casing through the build section and a 159 mm open hole lateral with 114.3 mm liner before evolving to a cemented-back monobore design. Analysis of the field data determined that 171 mm vertical and build sections of the wellbore, and a 159 mm open hole lateral with 114.3 mm casing is the optimal cemented-back monobore design, allowing for easier casing installation and providing substantial cost savings by eliminating the intermediate casing. Monobore ball-drop completion systems require a stage tool to cement from the heel of the well back to surface. By implementing a stage collar that closes mechanically rather than with a wiper plug or dart, the operator was able to reduce wellbore integrity risks and considerably lower drill-out costs before stimulating the well. The operator has completed more than 220 wells using this stage collar with 100% success. The geology of the upper formations was managed using invert drilling mud to control wellbore stability and downhole pressure, rather than intermediate casing, to successfully adopt a cemented-back monobore well design. The steps detailed in this paper to eliminate intermediate casing from wellbore construction, identify optimal wellbore sizes and reduce drill-out costs have proven to be successful in the field and can be applied to a variety of formations around the world.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".