Tubing Design: 2017 #74

Problem 74: A 16,000 ft tubing string has 5,010 psig on the tubing at surface and 10 psig on the annulus at surface. The mud weight in the tubing is 7.6 lb/gal and 8.2 lb/gal in the annulus. Which of the following statements is most FALSE? (for full wording see exam due to space limits here): (A) Collapse failure is a likely...; (B) Burst pressure is 500 psig...; (C) Collapse pressure is 6,800 psig...; (D) Burst failure is more likely...

The wording on this problem is deliberately vague. What is known: burst failure is not more likely the deeper one goes. Why? a) pumping down tbg creates higher pressure at shallower depths to overcome friction loss and b) additional string weight weakens the tbg more at shallower depth than deeper. So (D) is a first-pass answer.

But do a quick check on the other options to be safe:
(A) is possibly true as pipe is weaker in collapse.
(B) is possible since there is even currently 500 more psi delta in the tbg at surface.
(C) is possible too since that's the current pressure on the annulus at 16,000 ft, and tubing pressure is more likely to change in the future. So none of these can be "most false" when compared to (D).

Drill Line Tension: 2017 #72

Given new 2.5 inch 6X19 Extra Improved Plow Steel wire rope, what is the maximum tension that can be applied to the fast line while remaining below the API recommended design factor: for a) stuck pipe, b) hoisting, or c) casing, respectively?

This can be quickly solved without leaving 1 RIG 5. What I like about this break strength table is that I combine data from multiple sources most likely needed in real life, and merely ignore the rest. Remember, you can always interpolate for a quick, rough check on the rarer sizes, and this table meets this need.

The break strength is shown to be 604M lbf. Next, see the note: Design Factor API recommends a minimum 3 for hoisting, 2 for casing or stuck pipe, respectively. So: 604M/2, 604M/3, 604M/2, or (A).

Axial Stress: 2017 #71

Problem 71. Which action places the most axial force on a joint of 9 5/8 inch 47 lb/ft N-80 casing?

(A) Falling in a vertical hole at ½ foot per second until an abrupt & level impact.
(B) Injecting 10 lb/gal mud into the casing at 400 psig.
(C) Pulling it through a hole with a  3  0.6 per 100 ft dog leg severity.
(D) A & C are within 30% of each other & create the most axial force

Note this entire problem is solved on 6 DTC 1 (GB).
Answers are merely multiples of GB examples (lbf):

Use casing: 9.625 od & 8.681 ID (Redbook).
Δσz − shock = 1,780(Δv) = 1,780(1/2 ft/s) = 890 psi (1/20 Guidebook example)...
Fshock = Δσz − shock(As) = 890 lb/in2 (13.572 in2) = 12M...

Solution: A: 12M lbf (1/20 GB w/ conversion), B: 24M (1/10 GB), C: 17M (1/10 GB)

Duplex Pump HP: 2017 #66

Problem 66: A duplex pump has a stroke length of 10 inches, a 5 inch diameter liner, and a ½ inch rod. The pump is old and in poor physical shape but still has excellent volumetric efficiency and generates pressure at 2,000 psia with ease at 50 44 SPM (strokes per minute). The pump’s hydraulic pump power is closest to: (A) 170 hp (B) 180 hp (C) 190 hp (D) 200 hp.

See 1 RIG 3.
3.14159*0.25*2*10*((2*5^2)-(0.5^2))*(1/231) = 3.38 gal/stroke.
(2000-15 psi)(3.38 gal/srk*44 srk/min)/1714 = 173 hp or (A).

Multiphase Choke Pressure: 2017 #61

A multiphase oil mix (GOR of 800 SCF/STB) flows through a 12/64-inch wellhead choke at 200 bfpd. Choke pressure equations (Gilbert, Ros, Baxendell, or Achong) are compared. The maximum pressure difference? (A) 175 psg; (B) 150 psig; (C) 125 psig; (D) 100 psig. 

See 8 FAC 2. All numbers are the same except flow is 400 bfpd. To check the answer: divide high/low answers (1405 Gilbert/1105 Achong) by 2 (703/553) and subtract: 703-553 = 150 for (B).

Of course this is just to check. Always do problems as if the answer is not hidden in the Guidebook...