Drilling 412 Assignment 3 Fall 2020 PDF

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Assignment 3...

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DRLG 412, Assignment #3 Hoisting, Drill Collars & Drill Pipe - Module 3 & 4 Name:

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Assignment Instructions: You must show your work to get full marks. The assignment is out of a potential 50 points. You will get 75% of the marks for showing all of the appropriate steps and 25% of the marks for the correct answer. Use the engineering tables provided for your pipe weights and yield stresses. 1. A triple drilling rig is drilling a 222.2mm main hole section. The BHA includes 9 stands of 178mm x 57mm drill collars and 12 stands of 152mm x 57mm drill collars. The average length of the drill collars is 9.5m. Calculate the available bit weight in kilograms if we are drilling with 1100 kg/m3 mud weight and we are using a 20% safety factor. Remember 1 stand of pipe in a triple rig is 3 joints. (20) ANS: Drill collar design: Safety factor, S.F = 20% = 1.20 Mud weight = 1100 kg / m3, B.F  0.8626 1 drill collar length = 9.5m Buoyed weight of drill collars needed = WOB /9.81 (F = Mg, M = F/g) Max bit weight = Buoyed weight / S.F = 1100/1.2 = 917kg Air weight = Buoyed weight / B.F Density = Mass / volume = mud weight = 1100 Kg / m3 Weight of 3 of 178mm drill collars = 3 * 165.6 = 496.8 Kg Weight of 3 of 152mm drill collars = 3 * 122.9 = 368.7 Kg 1. Buoyancy Factor (BF) = 1 – MW (kg/m3 ) = 1 – (1100)/7848 = 0.8598 7848 2. Air weight = (Bit weight * S. F) / B.F = (917*1.2)/0.8598 = 1280kg Air weight = Buoyed weight / B.F 3. Buoyed weight = Air weight * B.F = 1280 * 0.8598 = 1101kg 4. WOB = Buoyed weight *9.81 = 1101 * 9.81 = 10801N 5. Total DC weight = Air weight / (1 – S.F) = (1280) / (1-0.2) = 1600kg Weight from 178mm = Total DC weight - smaller collar weight = 1600 – 368.7 = 1231.3kg Number of 178mm DC = 1231.3/496.8 = 2.47  3 (since the rig is a triple) 3, 152mm, weight =368.7kg Summary of the DC Design: 3, 178mm, weight = 1231.3kg 3, 152mm, weight =368.7kg

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2. Using all of the information from the previous question, what is the length of the BHA? Total DC in the previous example = 3, 178mm with 3, 152mm DC = 6 DCs * length of 1 DC = 6 * 9.5 = 57m 3. If you are drilling in a hard or rough drilling area where bit bounce is a problem, what change in your drill collar design in question 1 would you implement. (I am not looking for any calculations, just a 1-line answer.) (5) ANS: Safety factor of 25% should be used.

4. The rig from question #1 has 280 joints of 127mm, 29.02 kg/m grade E drill pipe and 250 joints of 127mm, 29.02 kg/m grade G drill pipe. The average stand length for all of the drill pipe is 28.80m. The drilling contractor has set a limit of 65,000kg as the maximum overpull margin for all drillpipe. How many joints of grade E pipe can we safely drill down and at what depth do we need to switch to grade G drill pipe. (NOTE: Ignore buoyancy and you must use whole joint lengths and not fractions of joint lengths. Drill pipe body yield, yield strength, body strength, & yield stress all mean the same thing.) (20) Grade E Number of joints = number of drill collars = 280 F = Mg = 65,000 * 9.81 = 637,650N – Maximum Yield stress = 179 439kg *9.81=1 760 297N – Overpull Margin = 65 000kg*9.81= 637 650N – Maximum Allowable Force = 1 122 647N – Maximum Load = 1 122 647 / 9.81 = 113 743kg – Drill Collar Load = 1600kg (from the example above) – Drill Pipe Load = 113 743 – 1600 = 112 143 kg – Length of Drill Pipe = 112 143 / 29.02 = 3864m – BHA length = Total length of the Drill collars in the example above = 57m – Total joint of Grade E drill pipe = 3864/57 = 68 joints - Maximum Depth = 3864 + 28.80 = 3893m

Grade G – – – – – –

Maximum Yield Stress = 251 215kg*9.81=2 464 419N Overpull Margin 65 000kg*9.81= 637 650N Maximum Allowable Stress = 1 826 769N Maximum Load = 1 826 769 / 9.81 = 186 215 kg Drill Collar and Grade E Pipe Load = 113 743kg (Maximum load from previous example) Additional Depth = (186 215 - 113 743) / 29.02 = 2497m

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BF= 1 – MW (#/gal) 65.5

or BF = 1 – MW (kg/m3 ) 7848

Common Drill Collar Sizes & Weights Drill Collar OD

Drill Collar Bore ID

Weight kg/m

4¾”/120mm 6”/152mm 7”/178mm

2¼”/57mm 2¼”/57mm 2 1/4”/57mm

69.7 122.9 165.6

9”/228mm 11’/279mm

3”/76.2mm 3”/76.2mm

285.7 445.0

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