A novel drilling solution, ‘Constant Bottomhole Pressure (CBHP) Managed Pressure Drilling (MPD) assisted Casing Drilling operation', was designed, planned and successfully executed for different operators on multiple directional wells in North America. These wells were otherwise not drillable either conventionally or with CBHP MPD using conventional drillpipe-BHA; and over the last few decades several operators tried and failed to reach the Target Depth (TD) on multiple occasions when drilling some of these formations.
One operator drilled in formations prone to severe faulting/fracturing and with very high permeability, while a different operator drilled through multiple weak zones interbedded with over-pressured and highly conductive regions. Both scenarios resulted in similar issues with fluid displacement, tripping/surge and swab, kicks and losses, running casing and cementing. The generic CBHP MPD solution with a conventional drillpipe-BHA even with ‘Anchor Point' CBHP MPD and its variations was not successful in either of these scenarios in drilling to the TD.
As demonstrated using case histories, the success in these projects was a result of combining two technologies – ‘CBHP MPD' and ‘Casing Drilling'. Pre-planning, understanding formation constraints, training, and having knowledgeable and experienced people involved, enabled safe and successful execution of CBHP MPD assisted Casing Drilling on these projects and helped CBHP MPD develop and reach new horizons.