Wellbore Integrity During Production and Drilling Risk Analysis in Gas Hydrate Bearing Sediments by Coupled THMD Model
Bibliographic record
Abstract
Abstract Wellbore integrity in a gas hydrate bearing formation during drilling and production is a great challenge in the energy industry since a complex thermal-hydraulic-mechanical interaction with decomposed solid hydrate process is involved. A wellbore temperature increase and/or depressurization process may induce additional stresses and thermal and fluid flows, which may trigger wellbore instability, sand production, and undesired fracturing. Production-related wellbore integrity issues such as solid production during wellbore depressurization or heating are also widely observed and studied. To understand the thermal-hydraulic-mechanical behavior with hydrate decomposition (THMD) process and to simulate the THM responses of hydrate gas bearing sediments to wellbore pressure and temperature variations under a given in-situ stress regime during drilling and production, a fully coupled THMD model is presented in this paper. The conceptual THMD model with simplified semi-analytical solutions for the induced stress, pore pressure, and temperature at the wellbore and inside the formation is discussed. A linear Mohr-Coulomb criterion is utilized to define the onset of the wellbore instability or plastic yielding when sand production defined by effective plastic strain (EPS) is considered with a cohesion dependent on hydrate saturation. Numerical method with Laplace transformation is used to solve the transformed homogeneous PDE. We conclude that thermally- and hydration-induced stresses will affect wellbore integrity during hydrate gas production due to wellbore pressure reduction and temperature increase. Unlike the stress perturbation in the conventional gas reservoir, critical temperature and pressure for the equilibrium phase change must be surpassed to induce additional incremental stresses due to the hydrate decomposition. Additional fluid mass and energy transfer may take place with induced temperature and pore pressure because of the hydrate decomposition/recomposition. In addition, the hydrate saturation changes due to the typical drilling strategy applied may reduce the hydrate formation significantly, which will affect the design of production pressure control and management. Thus, pressure optimization is crucial for both maximum production and wellbore integrity.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 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".