Natural Gas Hydrate Equilibria in Brine Including the Effect of Inhibitors on Hydrate Formation
Bibliographic record
Abstract
Abstract Preventing hydrate formation is critical to safely and economically manage subsea tiebacks. Thermodynamic Hydrate Inhibitors (THI) and Low Dosage Hydrate Inhibitors (LDHI) help manage hydrate formation. Here, we use a novel isothermal approach using a PVT cell to experimentally find the hydrate equilibrium point of natural gas and brine. In addition, a constant temperature and pressure condition is used to compare hydrate formation with and without hydrate inhibitors. First, to better understand the novel isothermal technique, natural gas-brine equilibrium experiments were conducted. Secondly, a constant pressure and temperature approach is used to investigate Kinetic Hydrate Inhibitors (KHIs) and low dosage methanol performance on hydrate formation. The formation and dissociation points are detected through a sudden drop or peak in the pressure profile, respectively, and by visual observation. To evaluate inhibitor performance, the experiments were conducted at challenging temperatures between -0.5°C to 3°C, applicable to the environment offshore Newfoundland and Labrador. Two commercial KHIs and one THI were tested. Both KHIs showed good performance up to certain level of subcooling according to their concentration. However, KHI-B performed better at inhibiting hydrates compared to KHI-A despite its lower concentrations compared to KHI-A. The induction time for 1 wt% KHI-A under 10°C subcooling at a temperature of 0.75°C was 311 min. The induction time for 1 wt% KHI-B under 12°C subcooling at a temperature of 2.66°C was 184 min. Yet, in the case of KHI B, with half the concentration (0.5 wt%), no hydrate formed at temperature of 1.21°C and 10°C subcooling. Low dosage methanol (a common THI) was also assessed. Although the induction time under 10.36°C subcooling and constant temperature of −0.43°C was only 47 min, no hydrate formed within 22 hours at −0.12°C under 7.5°C subcooling. This work uses a novel experimental isothermal approach by PVT cell to investigate hydrate equilibrium and the effectiveness of different inhibitors. Hence, a better understanding of natural gas hydrate equilibrium in brine is developed. Based on significant costs associated with injecting high quantities of THI (e.g., methanol) to prevent hydrate formation, this work also compares the performance of KHIs and low dosage THI (methanol).
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".