Bibliographic record
Abstract
Abstract With the high demand for oil and gas, operators are becoming increasingly interested in unconventional sources of hydrocarbon. One of the major sources in the world is heavy oil, which has been defined by the API as oil that has API gravity of less than 22.3 °API at 15.6 °C (60 °F) (extra heavy oil, or bitumen, has 10 °API or less). Because heavy oil does not flow on its own in the wellbore, a mechanism must be used to recover the oil by making it mobile. Among the different experimental and operational methods, steam-assisted gravity drainage (SAGD) has been the method of choice for the past few decades. This process uses steam to heat the immobile oil and reduce its viscosity so it can be extracted, usually by using pump jacks. These heavy oil wellbores need to be zonally isolated to help ensure that the reserves are produced properly without environmental or production optimization challenges. In Alberta and Saskatchewan, many wells are drilled and cemented in designated heavy oil fields where SAGD is applied to stimulate production. Most of these wells are successfully cemented, however, some wells experience zonal isolation failures that result in steam breakout or steam loss into non-targeted zones. While the problem may be related to the primary cement job, it may also have been created by post-cementing operations and/or conditions. Sometimes the problem may be temporarily solved by conventional methods, however, the ultimate remedy may have to be applied eventually. The long-term integrity of the cement sheath behind the casing should be planned with drilling, completion, production/injection and abandonment stages considered. A properly designed and engineered cement slurry system can help save a wellbore/field from additional unplanned expenses. The process is shown below:Cement slurries are designed under defined wellbore conditions and exposed to field conditions in the laboratory.The mechanical behaviour of the cement sheath under downhole conditions is studied using three-dimensional, finite element analysis software.The endurance of the cement sheath under applied conditions is predicted and optimized.Operation and placement of the selected slurry is studied to help ensure optimum execution. Stresses exerted on the cement sheath from wellbore operations during construction, injection or production that could damage the cement sheath are integral to the study. These conditions are analyzed to help engineers understand the post-cementing operational effects on the sealant system. This paper presents the design criteria for finding the fit-for-purpose sealant systems that can successfully protect wellbores under harsh environmental conditions of SAGD and cyclic steam stimulation (CSS) operations. Introduction The long-term integrity of a cement sheath throughout a well's life is the ultimate factor for determining whether the sealant will withstand the planned operations, production and injection that are planned for the well. In the case of heavy oil operations, the primary design considerations for a long-lasting sealant are the temperature and pressure regimes. The stresses caused by the extreme changes are exerted on casing, cement and the rock.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
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".