Laboratory Testing of Novel Sealant for Leaky Wells
Notice bibliographique
Résumé
Abstract Many abandoned gas wells in western Canada leak gas to the surface. This paper presents the results of an experimental study to determine the possibility of using an asphalt-in-water emulsion as an efficient sealant for these abandoned leaky wells. A second application of this process would be to hinder the water flow from water producing formations. The asphalt-in-water emulsion used in the experiments had asphalt particles with an average particle size of around 4 μm and a 60% internal phase concentration. The emulsion exhibited a pseudo-plastic behaviour. Its viscosity ranged from 60 mPa •s at a shear rate of 60 RPM to 145 mPa •s at a shear rate of 6 RPM. The emulsion was found to be stable, even though it settled with time. Its original properties were retained after agitation and settling had occurred. Core flow experiments were performed in order to simulate injection in the near-wellbore region. The cores were prepared using silica sand with a 60 to 80 mesh size. The resulting cores had a porosity range of 25 to 32% and a permeability range of 2.5 to 9 Darcy. Experiments were performed under varying injection pressure conditions. In each case, solid plugs were formed and their length in the porous medium increased as a function of the injection pressure. In order to extend the length of the plugs, several anionic surfactants were tested as pre-flush solutions for conditioning the surface of the sand grains. This resulted in increasing the emulsion penetration into the cores. The basic mechanism of the process is to pressure up the emulsion next to a formation, forcing the emulsified asphalt to enter the porous medium and to form a flexible sealing plug. We surmise that the plug is formed through a combination of two pore blocking mechanisms: one by blocking the pores by the larger-than-pore droplets, and the other by adsorbing onto the sand grain surfaces. The experimental results showed that an asphalt-in-water emulsion can be successfully used to seal gas or water production from a high permeability formation. The study concludes with recommendations for further research required to implement the process in conventional or tight gas formations. Introduction Proper well abandonment is the final and critical step in the process of natural gas and oil exploitation. Depleted oil and gas wells produce small non-economic amounts of gas, often the result of gas migration either through the cracks, fractures and voids in the formation along the outer wall of the casing, or between the original cement and the formation. The gas may escape to the atmosphere by flowing around the surface casing or migrate into shallow aquifers. The current procedures for well abandonment involve placing a cement plug over the production zone and maintaining a column of water from the top of the plug to the surface. Sometimes, these procedures may not seal off all of the producing zones and remedial well abandonment treatments are needed. The Alberta Energy and Utilities Board indicates that there are more than 3,000 orphan gas wells, many of which are leaking gas to the surface.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».