Challenge: Reduce trouble time and well cost due to lost circulation in severely depleted gas sands in a mature onshore field where the pore pressure/fracture gradient margin can be as narrow as 0.5 ppg. Reduce the equivalent circulating density (ECD) as low as possible without taking kicks.
Solution: Use liner and casing drilling to reduce mud weight, eliminate swab/surge, and eliminate heavy overbalanced trip margins. Use the dynamic annular pressure control (DAPC) system together with the HOLD rotating control device (RCD) to reduce the static mud weight below pore pressure and manage the backpressure to maintain the BHP above pore pressure during connections and cementing.
Results: Reduced drilling time by as much as 7 days in one well. Reduce drilling cost by USD 500,000 compared to a comparable offset well conventionally drilled with gas kicks, lost circulation, and high NPT.