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

Abstract

Summary Drilling in the North Sea is confronted with an ever more challenging pressure-management issue because of narrow geopressure windows in depleted reservoirs. Further, the occurrence of packoffs can cause serious damage to the formation and contribute to nonproductive time. To address these problems, automation of mud-pump management has been developed over the last 4 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 (e.g., depth, temperature, flow-rate, gel time, cuttings proportion), the necessary safeguards 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. On the basis of the current context, evaluations 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-startup procedure has been semiautomated to decrease connection time. Finally, an automatically triggered pump-shutdown procedure is also available to minimize the consequences of a packoff 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 rigsite is necessary before such automation can be rolled out safely.