Drill Pipe
Exercises
1. Drill pipe strength is measured in terms of (choose one)
- Torsional yield strength
- Tensile yield strength
- Collapse resistance
- Internal yield
- (a) and (b) only
- (a) and (c) only
- (a), (b), (c) and (d)
Solution
Drill pipe strength is measured in terms of torsional yield, tensile yield, collapse resistance and internal yield.
2. You are designing a drill string for a new well, and have the option of using one of the following types of drill pipe:
4 1/2′′ , 16.60 lb/ft , Grade E, Internal-External Upset, with NC46 (XH) tool joint
4 1/2′′ , 16.60 lb/ft , Grade 95, Internal-External Upset, with NC46 (XH) tool joint
The drill string is to be used for a vertical well with a projected depth of 15,000 ft. The length of the bottomhole assembly will be 1270 ft, with a weight of 125,000 lb.
Based on tensile yield strength only, which grade of drill pipe should you use? As a safety factor, assume that there is no buoyancy (that is, use the weight of the string in air).
Solution
Tensile stress will be a maximum at the top joint.
Step 1: Calculate the total weight of the drill string in air.
Total weight = (weight of bottomhole assembly) + (weight of drill pipe)
Total weight =(weight of bottomhole assembly)+(weight of drill pipe)
Total weight =125,000+[16.60⋅(15,000−1,270)]=352,918 lbs
Step 2: Compare the total drill string weight to the tensile yield strength of the drill pipe.
- Cross-sectional area of 4 1/2; drill pipe body =
- Grade E: Minimum tensile yield = 75,000 psi ; joint yield strength = 4.407⋅75000=330,558 lb; less than total weight of string
- Grade 95: Minimum tensile yield = 95,000 psi ; joint yield strength = 4.407⋅95000=418,707 lb; greater then total weight of string
On the basis of drill pipe body alone, we must use Grade 95 pipe.
3. You are inspecting a string of drill pipe that has just been delivered to your rig, and notice a series of five markings stencilled at the base of the pin on a tool joint.
Explain what each marking means.
Solution
First marking: Company symbol.
Second and third markings: Month and year, respectively, that the tool joint was welded.
Fourth marking: Pipe mill code
Fifth marking: Pipe grade code
4. Determine the internal capacity of the following drill string:
Drill string:
7,800 ft of 5″, 19.50 lb/ft drill pipe (capacity = .01776 BBL/ft)
900 ft of 8″ OD, 150 lb/ft drill collars (capacity = .00735 BBL/ft)
Solution
Pipe capacity=(7800′⋅0.01776)+(900′⋅0.00735)=145.14 BBL
5. You notice some joints of drill pipe on the pipe racks that have red bands painted on the pipe body. Should these joints be picked up in the drill string?
Solution
The red bands indicate that these joints are scrap. Do not pick them up, but have them removed from the racks.
Assessment
1. The length of Range 2 drill pipe, which is the one most commonly used, is:
A .18-22 ft
B .27-30 ft
C .30-37 ft
D .38-45 ft
2. Collapse resistance is:
A .Resistance to twisting force
B .Resistance to axial tension
C .Resistance to external pressure
D .Resistance to internal pressure
3. Which of these statements about drill pipe tool joints is FALSE?
A .Tool joints are fabricated separately from the drill pipe tube and then welded on at the upsets.
B .A Full Hole (FH) tool joint corresponds to an API NC-40 numbered connection.
C .Tool joint specifications usually include information on recommended makeup torque.
D .Five threads per inch is the standard for fabricating tool joints.
4. Of the five markings that identify tool joints the third one:
A .Designates the pipe mill code
B .Designates the month in which it was welded
C .Designates the company symbol
D .Designates the pipe grade code
E .Designates the year in which it was welded
5. What would be the annular capacity, opposite the pipe body, for a 9 7/8-inch hole containing 5-inch, 19.50 lb/ft drill pipe?
A .0.0242 bbl/ft
B .0.0586 bbl/ft
C .0.0704 bbl/ft
D .0.0897 bbl/ft
6. Which of these is NOT a recommended guideline for proper drill pipe handling?
A .After inspecting pipe on the racks and applying thread compound, re-install the thread protectors before moving the pipe onto the catwalk.
B .When breaking connections, use the weight of the drill string as a back-up to keep the pipe from turning in the rotary table.
C .Make up connections slowly to prevent galling of threads.
7. “Required” API procedures for inspecting tool joints include:
A .Outside diameter measurement
B .Box swell measurement
C .Magnetic particle inspection
D .A through C
E .B, and C
8. In a vertical or “straight” hole, the portion of the drill string that is most subject to bending is __________________.
A .just below the uppermost drill collar
B .several stands below the surface, in the drill pipe body
C .in the pipe body, roughly halfway between the rotary table and the bottomhole assembly
D .in the tool joint, roughly halfway between the rotary table and the bottomhole assembly
E .in the tool joint nearest to the drill collars
F .in the drill pipe body just above the tool joint nearest to the drill collars.
9. What is the endurance limit of a material?
A .The stress that causes immediate failure of a material.
B .The stress at which cracks in the material become visible.
C .The stress at or below which the material will not fail, regardless of how many stress cycles it undergoes.
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