Identification of Environmental Effects of Acid Gas Injection Using X-Ray Computed Tomography
Notice bibliographique
Résumé
Abstract With the increasing trend to dispose acid gases (H2S and CO2) generated from natural gas processing, by geologic sequestration, industry and government must carefully assess the compatibility of the rock formation and fluids with the intended injection stream to ensure safe and efficient facility operations. Recent geochemical analysis of carbonate cores, previously subjected to acid gas core displacement tests, prompted an examination of changes to porosity using x-ray computed tomography (CT). Results indicate that increases in porosity may be linked with the increases in permeability observed during the core injectivity testing. Visually distinct areas in the core suggested that changes were non-uniform implying regions of higher consolidation representing lower permeability. In addition, when several voids were subjected to detailed CT image analysis, we observed traces of halite (NaCl) crystals probably resulting from the desiccation of formation water by the extremely dry acid gases. This suggests that the increase in porosity could not be attributed to dissolution processes, but due to fine dislodgement of materials during the high pressure injection. Inadvertently, the permeability increases were resultant of both desiccation effects and particle dislodgement. Introduction Acid gas injection has been accepted as a practical way to dispose of the undesirable H2S and CO2 (acid gases) produced from natural gas processing. This technology allows the production of sour gas reservoirs to be economically viable and provides an environmentally friendlier option in comparison to other disposal alternatives. In order to successfully dispose of the acid gas in a safe and efficient manner, the process of selecting an adequate disposal formation includes assessment of various reservoir conditions in order to determine suitability. One of the requirements is to examine the compatibility of the mineralogy of rock formation and its fluid with the injection stream, usually accomplished through core sensitivity tests. Core Sensitivity Tests The objective of the core sensitivity test is to observe any significant changes in permeability, to ensure that impairment to injection will be minimized. This test is essential because of the potential to damage the formation as a result of the acid gas injection which could jeopardize injection or containment within the formation. Some potential formation effects which may include but is not limited to; desiccation, dissolution and dislodgement of fine materials (1). Desiccation occurs when the formation fluid has significant salinity and the acid gas stream is highly understaturated in water resulting in a salting out effect as the injected stream reduces the initial brackish pore fluids. Dissolution takes place when acid gases dissociate in formation fluids decreasing the pH and increasing the natural water-rock reactions of the reservoir. Fine dislodgement is generally experienced in poorly consolidated cores when subjected to the injection pressures and increased flow rates over the small surface area of the pores. An ideal core would be sufficient in size to allow for monitoring of all of these effects, especially the geochemical effects of dissolution and re-precipitation, if they occur (1). Unfortunately, in practical applications the selection of cores to choose from is limited when using a previously producing well to inject into a depleted hydrocarbon reservoir.
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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 | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 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 ».