1. A casing string of 7O.D, is to be lowered to 9500 in 8.5 hole, 95/8 casing (I.D.8.68) is set at 7500. The well is filled with 11.0ppg mud, casing is fitted with float shoe and lowered empty. Pipe is 26 \# grade N80. a. Calculate the collapse resistance safety factor if the pipe is lowered empty till total depth (9500'). Casing collapse resistance is 5410 psi at zero tension b. To reduce collapse stresses, the pipe is filled with mud, how much mud should be put inside casing to have 1.25 collapse safety factor? c. Calculate the minimum tensile safety factor for empty pipe and for pipe filled with 90bbl of mud, shoe at 9500 ', and joint strength =519,000lb