A drilling rig uses a hoisting system to drill wellbores. After drilling a 25,000 ft well, it is established that the drilling bit needs to be replaced by tripping out (i.e. pulling out). The available engine horsepower for this operation is 3500 hp.

1. 1. Considering the following data, estimate the maximum travelling block speed when the length of drilling string is 1500ft.
      1. Average drag force is 0.0025 ???/?? per 1 ??/??? speed of drillstring,
      2. Weight per foot drill pipe = 22 lbf/ft,

• Weight per foot of drill collar = 170 lbf/ft,

1. Length of Drilling collar= 1200 ft,
2. Mud weight is 10 ppg,
3. Hoist efficiency is 79%

• Drawworks efficiency is 81%.
• Drillstring density is 65.5 ppg

1. Neglect the weight of the bit.
2. While pulling the drilling string out of the well, a fracture is created at the depth of 2000 ft where pore pressure is 880 psi and mud loss occurs until pressure equalises at that depth. Determine the height of mud column in the well after losing mud into the fracture.
3. Redo part A considering the calculated mud height in part B.