Monitoring and control of bottomhole pressure during surge and swab operations using statistical process control

This article for the first time uses a mixture of Statistical Process Control and Engineering Process Control to identify, monitor and control assignable and common causes during drilling operations. To this end, Control charts are applied on the output of the process controlled using EPC and points outside of the predefined control limits are identified. This method can use controllable input variables not used in EPC such as changes in weight of fluid entering the well, to fully control the process. The results show improvements on limits of EPC method using SPC for controlling bottomhole pressure in the acceptable range.