Real-time Downhole Monitoring and Logging Reduced Mud Loss Drastically for High-Pressure Gas Wells in Tarim Basin, China
Notice bibliographique
Résumé
Abstract This paper describes a real-time case study to prevent mud loss and blowouts while drilling a high-pressure gas well in Tarim basin, China. The complex geological structure, high tectonic stresses, and overpressured and fractured reservoir formations in the field present a huge challenge to drilling. Of the seven wells drilled in the field in 2005, two did not reach target depths, four experienced huge mud loss, and the other experienced a blowout resulting in lost control of the well. In early 2006, PetroChina teamed up with Schlumberger and Petroleum University of China to form a collaborative technical group to develop a better understanding of mud loss and blowout mechanisms. The key component of the study was to establish a geomechanical earth model based on offset well data prior to drilling, update the model using downhole monitoring and logging data during drilling, and predict a safe mud weight window in real-time. Real-time prediction of a safe mud weight window with annular pressure monitoring helped ensure that downhole annular pressure was maintained within the safe mud weight window during drilling and tripping. The study resulted in a 20-times reduction in mud loss and 10-times reduction in nonproductive time, and elimination of an extra casing. A better understanding of mud loss/blowout mechanisms was achieved and guidelines for preventing mud loss/blowouts specific for this gas field were developed. Introduction The target well is located in a highly fractured complex geological structure with abnormally high pore pressure in reservoir section. Of the seven wells drilled in 2005, two did not reach the target depth due to over pressure. Huge mud loss (averaged approximately 1500 m3 per well) was experienced in the other four wells. The mud loss was responsible for 42% of total drilling incidents, significant non productive time (33.38% of total NPT) and over budget (see Figure 1). An underground blowout occurred in a recent well resulted in lost control of the well. It has been observed that a mud weight slightly too high could hydraulically fracture the borehole and result in significant mud losses, and a mud weight slightly too low could lead to blowout with potentially disastrous consequences. It is therefore critical to be able to predict, in realtime, the extremely narrow safe mud weight window so that necessary measurements can be taken to mitigate the risks. In early 2006, PetroChina teamed up with Schlumberger and China Petroleum University to form a collaborative technical group to develop a better understanding of mud loss and blowout mechanisms. Based on the technical group's suggestion, a real-time pore pressure monitoring was conducted for an appraisal well to be drilled in 2006 in the field. The study primarily consisted of three stages - pre-drill planning, execution during drilling and evaluation post drilling. The key task of this process was to build and update a Mechanics Earth Model (MEM), which formed the basis for safe mud weight window prediction.
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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 ».