Q1: (20 Points) A 10% inch surface casing is to be set at 4500 ft with 10.6 ppg mud in the hole. Design the casing to achieve minimum cost. Only casing grades C-75 and J-55 are available. Burst Design: Assume an injection pressure that is equivalent to 0.4 ppg greater than the fracture gradient and a safety factor of 1.15. Assume the fracture gradient at 4500 ft is 0.75 psi/ft. Assume the casing is filled with formation gas which has a gradient of 0.1 psi/ft. Assume the external (backup pressure) outside the casing that resists burst is the normal pore pressure which has a gradient of 0.45 psi/ft. Collapse Design: Assume a lost circulation zone below the shoe which has zero pore pressure. Assume a safety factor of 1.1. Tension Design: Assume maximum tension is due to the weight of the casing. Assume a safety factor of 1.6.