Abstract
Drilling wells with Managed Pressure Drilling (MPD) technology allows Operators to drill and complete wells that would be otherwise un-drillable or uneconomical when done conventionally. The use of a mud density below the pore pressure can significantly reduce the likelihood of partial or complete loss of circulation especially when drilling through possible fracture or weak zones for Deep Disposal well projects.
While drilling a Deep Disposal well, pore pressure was determined and confirmed through fingerprinting with the use of surface-applied pressure on connections. Drilling deeper into a different formation, total loss of circulation was experienced. The loss of mud in this scenario, without returns to the surface, can cause the fluid level to drop over time leading to a potential wellbore influx, that could result in the influx reaching surface. However, due to cross-flow between the high pressure zone and the loss zone, gas from the high pressure zone was not seen on surface. Managing these losses involved the successful placement of Loss Circulation Material (LCM) to re-instate circulation and the use of Managed Pressure Cementing procedures to set cement plugs to heal the loss.
This paper delves into this unique instance of how MPD techniques were utilized to manage this cross-flow event in the Deep Disposal well in Alberta while highlighting the safety considerations employed when deciding between changing wellbore fluid to Brine or maintaining Invert as wellbore fluid.
