This paper summarizes a quantitative risk assessment (QRA) performed on a new generation blowout preventer (BOP) and multiplexed control system to be used in water depths of up to 10,000'. Prevention of severe environmental damage and minimizing danger to personnel are the critical functions of a BOP. In order to assure high reliability in the systems, a risk assessment was performed on the design before final assembly. The reliability was examined in two manners, by development and quantification of a fault tree model of the systems and the development of a failure modes and effects analysis (FMEA). Both techniques yielded basically the same results, however the FMEA benefited from the insights gained during the more rigorous interdependency evaluation from the fault tree analysis. Application of QRA techniques can be used to improve the reliability of critical systems. The use of these techniques during the design phase allows reliability concerns to be addressed prior to initial system operation. The techniques are applicable to all types of automatic and manually operated mechanical, electrical, and control systems. The reliability of the systems examined is high due to the large amount of redundancy and continuous status monitoring of the system components. Component specific failure data was limited due to the uniqueness of the design, however representative data was developed based on generic sources, discussions with designers, and engineering judgment. The failure combinations, called cutsets, were reviewed with the designers to ensure that the model accurately reflected the systems. Importance measures were used to assess the relative importance of the various design features and the sensitivity of the results to the assigned failure data. Although the reliability of the BOP and control system was sound to be high, several recommendations resulted from the analysis results to improve or maintain the high level of reliability. Introduction Hydril Company has developed and built a blowout preventer (BOP) and control system for installation and operation onboard the Transocean Offshore Inc. drillship Discoverer Seven Seas. The BOP is designed for deepwater drilling operations up to 10,000 feet below sea level and incorporates the latest technology advances in micro-processors to increase system flexibility, system diagnostics, reduction in the electronic component count and the physical size required to house the components. In order to assess the overall reliability of the system, EQE International has developed and quantified a fault tree model as part of a quantitative risk assessment (QRA). The QRA process is composed of the following subtasks which are discussed in more detail following the backgrounddiscussion:Success Criteria Determination,System Boundary DefinationFault Tree DevelopmentFault Tree Quantification, andResults Interpretation Background BOP control system changes have been brought on by advances in technology and by the demand for increased capabilities associated with the control system:The new deep water stacks have more functions and monitoring capabilities which exceeds the capacity of the older control systems.The new multiplexed (MUX) control systems are software driven, computer based, networked systems. The operation, maintenance, and trouble shooting of the new MUX control system is significantly different from the older control systems.
A proprietary design using a pyro-mechanical, electrically initiated, kinetic energy enabled shearing action has safely and reliably delivered on the promise of "Shear Anything" and seal successfully. The kinetic blowout stopper (K-BOS) will shear anything in the well above the bit thus eliminating non-shearables from the oil & gas lexicon. Further a superior clean fish with minimal deformation is produced by the kinetic shearing action. The K-BOS will shut-in full flow and pressure blowouts in milliseconds with its simple protected hermetically sealed construction for unparalleled post–shearing sealing performance and dramatically reduce extremely deadly and damaging flammable and/or toxic gas releases. With unrivalled confidence and reliability with best-in-industry control system monitoring and function testing and actuation techniques, the K-BOS requires virtually zero maintenance because of its simple construction where the working components are not wetted by wellbore fluids until actuation, meaning lower costs and reduced NPT and downtime. Like the automotive air bag, the K-BOS is self-contained and meets US and International deregulation requirements regarding safety and logistics of pyrotechnic devices. Starting with ballistic modeling technology developed for the military, the models were adapted to the K-BOS application and predicted the outcomes of shearing tests with different common tubulars including traditional "unshearables." A testing regime has been conducted to validate the models, demonstrate repeatability of the results, and demonstrate that a post shear seal could be achieved. More than 30 test serials with the K-BOS 4-1/16″ prototype including empty well-bore tests, shear tests ranging from 5/16″ wireline to 3-1/2″ Drill Collar with a 1″ Wall Thickness. All tests to date have sheared the target tubular without failure. Multiple materials and configurations have been tested. In all the shearing tests, the K-BOS successfully sheared the target while achieving all safety objectives. The shear test program has validated the models and has also provided validation data allowing for adjustments to the modeling technology for this specific application and resulting in a high level of accuracy and precision in design and shear performance expectations. The shear testing also showed that the K-BOS can shear without damaging the seals and provides an adequate sealing surface after shearing. The K-BOS has successfully met technical readiness level 5 (API 17N scale) and is ready to move on to in the field scale shear and seal testing. These results and the continuation to continuing development further the prospects of ensuring the K-BOS achieves its mission to strengthen the industry's social license to operate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.