Automation of Mud-Pump Management: Application to Drilling Operations in the North Sea

Abstract

Abstract Drilling in the North Sea is confronted with an ever more challenging pressure management issue due to narrow geo-pressure windows in depleted reservoirs. Further, the occurrence of pack-offs can cause serious damage to the formation and contribute to non-productive time. To address these problems, automation of mud pump management has been developed over the last four years to minimize the chance of fracturing the formation while starting the mud pumps or circulating. To account for abnormal flow restrictions in the annulus, automatic actions are also an integral part of the mud pump automation described in this paper. Since the downhole conditions are continuously changing (depth, temperature, flow-rate, gel time, cuttings proportion, etc), the necessary safe guards to operate the mud pumps need to be updated constantly. Advanced transient temperature and hydraulic models are used to estimate, in real-time, the downhole situation. Based on the current context, evaluation of maximum pump rates and acceptable flow accelerations are performed and sent to the mud pump control system to be used as an envelope of protection. Furthermore, to assist the Driller during connections, the pump start-up procedure has been semi-automated in order to decrease connection time. Finally, an automatically triggered pump shutdown procedure is also available to minimize the consequences of a pack-off on formation fracturing. A first version of the system has been tested during the drilling of one well in 2008 in the North Sea. Based on the initial experience, a revised version has been used during the drilling of three wells drilled on the Norwegian Continental Shelf in 2009. The feedback from the Drillers involved in the testing has been used to improve the user friendliness of the system. The automation of the mud pump management has been well accepted by the drilling crews. However, the testing has shown that additional instrumentation at the rig site is necessary before such automation can be rolled out safely.