Search

Abstract Mud loss is the most serious formation damage in oil and gas well drilling engineering and is an unsolved technical problem. To prevent mud loss, it is necessary to accurately understand and identify three key factors of mud loss, including the location of the loss, the time of occurrence, and the severity of the loss. The diagnosis of mud loss is a prerequisite for the proper formulation of mud loss control techniques. It emphasizes the integration of predrilling, drilling, and postanalysis information to describe and characterize loss zones and predict potential loss zones. On the basis of the theory of engineering fuzzy mathematics, we develop a mathematical model for loss probability evaluation that combines logging anomaly features and engineering data to predict the location of losses from drilling mud and develop a loss formation identification method. The study of hydraulic fracture deformation through stress‐sensitive experiments and numerical simulations can predict the deformation and severity of loss channels, which can help optimize the loss of circulating material by adding drilling fluid. Loss pressure models have been developed based on mud loss mechanisms, and loss pressure for hydraulic fracture creation, connection, and extension has been studied to help identify loss mechanisms and types. Mud losses can be identified by unusual engineering characteristics, including sudden changes in drilling times, cuttings, and mud logging. Real‐time logging parameters can be used to monitor the loss process and hence predict the loss trend. The framework of loss diagnosis techniques is established, which helps in successful mud loss controlling.

Mud loss is the most serious formation damage in oil and gas well drilling engineering and is an unsolved technical problem. To prevent mud loss, it is necessary to accurately understand and identify three key factors of mud loss, including the location of the loss, the time of occurrence, and the severity of the loss. The diagnosis of mud loss is a prerequisite for the proper formulation of mud loss control techniques. It emphasizes the integration of predrilling, drilling, and postanalysis information to describe and characterize loss zones and predict potential loss zones. On the basis of the theory of engineering fuzzy mathematics, we develop a mathematical model for loss probability evaluation that combines logging anomaly features and engineering data to predict the location of losses from drilling mud and develop a loss formation identification method. The study of hydraulic fracture deformation through stress‐sensitive experiments and numerical simulations can predict the deformation and severity of loss channels, which can help optimize the loss of circulating material by adding drilling fluid. Loss pressure models have been developed based on mud loss mechanisms, and loss pressure for hydraulic fracture creation, connection, and extension has been studied to help identify loss mechanisms and types. Mud losses can be identified by unusual engineering characteristics, including sudden changes in drilling times, cuttings, and mud logging. Real‐time logging parameters can be used to monitor the loss process and hence predict the loss trend. The framework of loss diagnosis techniques is established, which helps in successful mud loss controlling. [ABSTRACT FROM AUTHOR]

Hard brittle shale in Shahejie Formation, Nanpu oilfeild, is the typical formation with wellbore instability. During drilling process, wellbore collapse and drilling leakage frequently occur. Currently, for wellbore instability in shale formation, most of researches focus on wellbore collapse with structural plane. However, in drilling process, due to rich structural planes, like bedding planes and fracture planes, drilling leakage in shale is serious, extremely restricting safe and effective drilling. Therefore, based on rock mechanical test, considering the characteristics of shale structural planes, combining mechanism of leakage from failure along matrix, failure along bedding plane or fracture and failure propagation, a novel model of loss of pressure in shale formation has been established, determining the distribution and influence factors of loss of pressure. Results indicate that bedding plane and natural fracture are typical weak plane, and are the major controlling factor of causing leakage in shale formation. Compared to homogeneity condition, loss pressure in shale with multiply structural planes is hugely smaller. Also, well trajectory with safe drilling is decreased, increasing the difficulty of drilling. Furthermore, under the influence of weak plane, it is unlikely to see the failure along rock matrix. Leakage firstly happens at natural fracture. Besides, natural fractures has larger influence on leakage compared to bedding plane. The research results can offer theoretical basis for drilling design in hard brittle shale formation, and also meaningful for safe and efficient drilling in shale formation. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)