An exploration well is to be drilled to a total depth of 16,000 ft. Relevant data are as follows: Drilling programme: 0 - 400 ft 26 in hole; 400 - 5200 ft 17 1/2 in hole; 5200 - 11000 ft 12 1/4 in hole; 11000 - 16000 ft 8 1/2 in hole. Mud programme: Down to 400 ft, mud weight is 65 pcf; Down to 5200 ft, mud weight is 67 pcf; Down to 11000 ft, mud weight is 73 pcf; Down to 16000 ft, mud weight is 87 pcf. Casing programme: 20 in casing to be set at 400 ft; 13 3/8 in casing to be set at 5200 ft; 9 5/8 in casing to be set at 11000 ft; 7 in casing to be set at 16000 ft. Formation fluid gradient: 0-5200 ft, Pf = 0.465 psi/ft; 5200-11000 ft, Pf = 0.48 psi/ft; 11000-16000 ft, Pf = 0.57 psi/ft. Table for Size, outside diameter (in.), Nominal 'weight (lb/ft), Grade, Coupling type: 20, 94, J-55, LTC; 20, 133, K-55, BTC; 9 5/8, 40, K-55, STC; 9 5/8, 43.5, N-80, BTC; 9 5/8, 58.4, L-80, BTC; 9 5/8, 58.4, P-110, BTC. Safety factors: Burst = 1.1, Collapse = 0.85, Tension = 1.8. The 12 1/4 in hole experiences a maximum, dog-leg severity of 4°/100 ft. Other sections of the well experience negligible deviation. Shock loads are to be included in the design of 9 5/8 in. Design suitable casing strings for 20 inch and 9 5/8 inch casing mathematically and by using graphs for the given hole sizes, taking into consideration the available casing grades and maximum expected pressures.