Unconventional Shale Hydraulic Fracturing Under True Triaxial Laboratory Conditions, the Value of Understanding Your Reservoir
Notice bibliographique
Résumé
Abstract The Montney Formation of the Western Canadian Sedimentary Basin has emerged as one of the most prolific unconventional resource plays in the North American unconventional space. The authors propose a novel method to better understand the failure mechanics associated with hydraulic fracturing through laboratory testing under true triaxial conditions. This adds essential fundamentals with respect to upscaled field hydraulic fracturing operations in the formation. A representative source rock block recovered from outcrop was prepared into a cube and hydraulically fractured in the laboratory under true triaxial stress conditions. Field outcrop mapping of this quarry has confirmed that samples collected are of the same geological time and spatially equivalent to the source rock (Zelazny et al. 2018). This novel laboratory experiment mimics a single stage open hole hydraulic fracturing using a slickwater system, composed of surfactant, friction reducer, and biocide as the injection fluid. Micro-computed tomography (μCT) scans were used to identify the presence of preexisting fractures and bedding planes. A mini-well was drilled to the center of the cube, parallel to the direction of the minimum principal stress (σ3) and along the strike of the bedding planes, such that there is a 5 mm long down-hole open cavity. The existing true triaxial test system at the University of Toronto was retrofitted to accommodate a custom designed mini-packer system. Stresses were applied hydrostatically, and then differentially until the stress regime, replicating the field observed reservoir depth at about 2 km depth, was reached. The bottom hole was subsequently pressurized by pumping the injection fluid through the mini-packer. The test was numerically modeled in three-dimensions using the hybrid finite-discrete element method (FDEM) with the mechanical properties input determined through a series of standard laboratory rock mechanics tests discussed within. Post-test μCT of the tested cube revealed a fracture trace, and scan contrast was enhanced by injecting the cube with 5% wt potassium iodide solution. Interestingly, the highest fluid pressure recorded is slightly higher than σ3 whilst the plane of failure is normal to the intermediate principal stress (σ2) direction, which is parallel to the bedding planes. The results of the mechanical tests and hydraulic fracturing under true triaxial stress conditions reveal the significance and dominance of the macroscopic features and material anisotropy in dictating the overall strength and fracture plane orientation. Features which were unaccounted for in classical reservoir mechanics and the numerical model simulation, resulted in higher than predicted fracture initiation and propagation pressures than the laboratory experiment. This laboratory test approach allows a convenient and flexible method to capture the influence of the reservoir stress regime and its interaction with the sample anisotropy. Coupled with numerical simulations that encompass such features, this framework can benefit the industry by reproducing typical behavior observed in the field; thus, enhancing, improving, and increasing the efficiency of hydrocarbon recovery.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 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) | 0,000 | 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 tête enseignante, 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 ».