The main purpose of this case study is to understand and evaluate how an innovative methodology for sending MWD surveys uphole, based on cessation of surface RPM rather than fluctuation of mud flow rate, leads to more effective and higher performance Managed Pressure Drilling (MPD) operations while decreasing wellbore stability and HSE risks.
Conventional directional surveys are taken based on recycling of the mud pumps: mud flow is decreased below the MWD turn-on rate in order to switch off the tool and trigger the survey, and subsequently increased above this rate to switch the tool back on and send the survey uphole. Surveying based on RPM cessation is a different technique that takes and transmits a survey when the MWD detects that the rotation has stopped. This eliminates the need to recycle the pumps to take surveys and enables directional surveying with a full, unchanged flow rate. This surveying approach complements and supports applied annular pressure MPD operations, as downhole pressure control during pump recycling is one of the most challenging and critical aspects of MPD performance.
Drilling data from several wells of a West Africa MPD project that utilized this approach was evaluated from a drilling performance perspective. It was concluded that significant step changes in MWD surveying time and wellbore stability management were achieved. This surveying approach particularly reduced drilling risks intrinsically linked with formation pressure management: the constant mud flow rate while acquiring the MWD survey means that the surge and swab effects were minimized, without adding extra stresses on the formation and maintaining the borehole stability profiles within the critical limits. Moreover, this was achieved with a reduction in surveying time, leading to reducing drilling costs for the operator.
This paper explores how the application of this novel method of directional surveying enhances the application of MPD drilling techniques and reduces MPD-related challenges. RPM cessation surveys allow operators and contractors to push the drilling operations envelope in scenarios wherein extra fluctuations in the mud flow add significant risks. Furthermore, new studies with regards to wellbore stability optimization and stuck pipe prevention will be triggered in conventional and non-conventional drilling projects.