Variations of Managed-Pressure Drilling Currently Practiced:Offshore Case Studies
Bibliographic record
Abstract
Abstract Managed Pressure Drilling in marine environments is well on the path of widespread understanding and industry appreciation of potential for the technology. From years of evolutionary development on land programs, particularly in the United States and Canada, a number of offshore drilling decision-makers have now become ‘first adopters’ of this technology with significant success and with good control of the well at all times during the drilling process. Perhaps the best way to quantify this statement is to mention that, to date, all first adopters of MPD from offshore rigs plan future MPD projects. Unlike conventional circulating drilling fluids systems that are open to atmosphere on the rig floor, MPD tools and technology enable the circulating fluids system to be likened to the hydraulic characteristics of a pressure vessel. Several variations of MPD enable the effective wellbore pressure profile (e.g., equivalent mud weight) to be adjusted significantly with mud in the hole at the time, particularly beneficial when drilling in narrow formation pore pressure to fracture pressure margins and when the pressure environment limits may be relatively unknown. One variation of MPD addresses severe loss of circulation and excessive mud costs. Another addresses employee health, safety and environmental aspects that may be associated with drilling with conventional opento- atmosphere mud returns systems at the rig floor. A closed and pressurizable mud returns system is the enabling technology for most, but not all, applications of MPD. Drilling with a closed mud returns system reflects a relatively modest step change from conventional methods; most offshore rigs can accommodate the specialized equipment space requirements, benefits vs. cost are attractive, and the‘MPD way of looking at drilling hydraulics’ is relatively easy for drilling decision-makers and regulatory agencies to comprehend. Therefore, this paper will speak only to the ‘lower hanging fruit’ MPD techniques that are enabled by drilling with a closed and pressurizable mud returns system orannulus. More precise pressure management throughout the wellbore is an objective of all variations of MPD. Unexpected downhole pressure environments may be dealt with more efficiently with enhanced control of the well and usually with less interruption to the drilling program when such surprises are encountered. An influx of formation fluids is not invited in MPD. Although some MPD tools and techniques are rooted in Underbalanced Drilling technology, this is a major distinction between MPD and UBD. A properly planned and implemented MPD program is likely to see fewer hydrocarbons produced to the surface that if the prospect had been drilled conventionally. This work will define MPD, introduce the audience to its unique terminology and explain its Variations with pressure-depth maps. As each variation addresses specific well construction and drilling challenges, examples of each that have been practiced to date will be described. In consideration of operator confidentiality, several that are in the advanced stages of planning willbe addressed only in very general terms.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".