SUPPLEMENTARY EXERCISES
(1) A 13|-in. surface casing to be set to a depth of 6,000 ft. The mud weight is 9.2 ppg, the expected formation pore pressure is 0.465 psi/ft and a bottomhole pressure of 4,600 psi is expected when drilling the next hole section. The design factors to be satisfied are: 1 for collapse. 1.2 for internal x’ield and 1.8 for tensile strength. Assume that all API J. K. L and P grades are available. Design this pipe for the worst possible loading conditions.
(2) Design a 9|-in. intermediate casing to be set to a depth of 10,500 ft. The mud weight and expected formation pressure are respectively: 9.8 ppg and 0.48 psi/ft. A bottomhole pressure of 7,570 psi is expected when drilling the next hole section (production pipe). Assume that all API K. L, X. С and P grades are available. Satisfy the same design factors used in Problem 1.
(3) Design a 7-in. production casing to be set to a depth of 13.500 ft. The expected mud weight and pore pressure are respectively: 11.5 ppg and 0.57 psi/ft. Assume a gas leak at the tubing hanger and satisfy the same design factors as in Problems 1 and 2. All API J, C,L, P and X grades are available.
(4) A 20-in. conductor pipe is to be set to a depth of 500 ft. Check the compres — sional load on this pipe if it is to support the strings designed in Problems 1, 2 and 3.
(5) The pore pressure and fracture gradient data shown in Table 3.31 is for a typical well. Develop a mud and casing program for this well and design individual casings based, in each case, on the assumption of worst possible loading conditions. Design factors for collapse, burst and tension are: 1.1, 1.2 and 1.8. All API casing grades are available.
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Table 3.31: Data for Question (5).
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