Transient Thermal Model of Drilling Fluid in Wellbore under the Effect of Permafrost Thaw during Drilling in Arctic Region
Bibliographic record
Abstract
Abstract The arctic could hold about 30% of the world's undiscovered gas and 13% of the world's undiscovered oil according to an assessment by the United States Geological Survey (USGS). While, arctic oil and gas exploration is faced with various challenges such as the extremely cold polar environment, the ice scour, the permafrost. Permafrost is the perennially freezing soil (actually freezing pore water), and it can be an important geologic hazard and constraint. Permafrost is very common in arctic region, about one-half of the total land area of Canada and Russia and 85% of Alaska is underlain by permafrost. Besides, sub-bottom permafrost is also wide spread phenomenon of Arctic offshore areas. At present, the traditional thermal models of wellbore use an algebraic approximation to describe the heat transfer between wellbore and formation. Thus a new model should be established considering the effect of permafrost thaw during drilling in arctic region. As a matter of fact, the phase change of ice in permafrost needs to absorb heat from wellbore which can have an effect on the wellbore temperature. At the same time, migration of water from warm to cold regions will happen during the process of the thaw of permafrost. The migration of water will have an effect on the temperature due to the heat transfer along with the water. In addition, temperature in wellbore can be negative after long shut-in time due to the extremely cold polar environment which could lead to the blocking of wellbore. In this paper, a transient thermal model of wellbore during arctic drilling is established considering the effect of permafrost thaw in this paper. On the basis of the new model, a simulation of an arctic well is made and some conclusion are made from the case study: The temperature fields in wellbore and permafrost interact with each other. Besides, the temperature in wellbore drops to negative due to the extremely cold environment after long shut-in time, and the drilling fluid in wellbore could be frozen consequently. Long shut-in time should be avoided during drilling in arctic region. The new model established in this paper can determine more reasonably the wellbore temperature in artic permafrost region than the traditional model. A method to determine the reasonable shut-in time is given in this paper which can provide safety guidance during drilling in arctic permafrost region.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".