Conventional vs. Casing Drilling Geometries (Courtesy SLB)
Prevailing pore pressure and fracture gradient determine the optimum casing design
Allows setting high-pressure conductor deeper
Allows larger tubing string, less back pressure, higher production
Casing drilling value: mitigate shallow hazards
Casing drilling's smearing effect and narrow annulus:
Higher circulating friction increases bottomhole pressure (Conventional vs. Casing Drilling Geometries)
Strengthens the wellbore by plastering drilling cuttings into the formation
Allows casing depths to be based on the prevailing pore-pressure and fracture gradients
Deepen the structural casing
Rapid growth of the shallow fracture gradient allows a deeper casing shoe for higher formation strength (and higher mud densities to mitigate hazards)
Fewer casing strings in the riserless section allow larger casing strings deeper in the well design
Mitigates the loss/kick cycle
Reduces the use of contingency casing strings
Larger drilling operating windows in the lower well sections
Decrease circulating friction, minimizing the fluid-loss/kick cycle
Create the opportunity for contingency casing strings
Larger hole section across the objectives
Larger completion
Increased production rates and improved economics
Reduced total well time — fewer hole sections and casing strings, with a single trip to drill the hole section and run casing