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3 May 2021
We are drilling a hole at a depth of 4,000 ft with an 8 ½ in bit and a mud weight of 15 ppg, where the formation is abnormally pressurised. Formation pressure is 2400 psi, therefore a casing should be run at 4,500 ft to seal off this formation. There are Grade C-75 and N-80 casings available, C-75 Grade is 20.00 lb/ft (ID=6.456”, OD=7”) and N-80 is 17.00 lb/ft (ID= 6.538”, OD=7”). Analyse if both, neither or one of the casing Grades can withstand the formation pressure and will not collapse at the reported conditions. Use the API formulas and tables
We are drilling a hole at a depth of 4,000 ft with an 8 ½ in bit and a mud weight of 15 ppg, where the formation is abnormally pressurised. Formation pressure is 2400 psi, therefore a casing should be run at 4,500 ft to seal off this formation. There are Grade C-75 and N-80 casings available, C-75 Grade is 20.00 lb/ft (ID=6.456”, OD=7”) and N-80 is 17.00 lb/ft (ID= 6.538”, OD=7”). Analyse if both, neither or one of the casing Grades can withstand the formation pressure and will not collapse at the reported conditions. Use the API formulas and tables