Many drill pipe failures occur in the drill stem because of fatigue damage previously accumulated when the failed joint of pipe was run directly above the drill collars. This accelerated fatigue damage is attributed to the bending stress concentration in the limber drill pipe rotating to the stiff drill collars.
Two factors that cause extreme bending stress concentration in the bottom joint of drill pipe are:
1. Cyclic tensional whipping that moves down through the rotating drill pipe into the stiff drill collars.
2. Side to side movement, a well as the vertical bounce and vibrations of the drill collars that are transmitted up to the bottom joint of drill pipe.
Drilco`s Heavy-Water drill pipe is an intermediate-weight drill stem member, with a tube wall approximately 1 in. (25.4 mm) thick. This compares to approximately 3/8 in. (9.5 mm) wall thickness for regular drill pipe and approximately 2 in. (50.8) wall thickness for drill collars. Heavy-water drill pipe provides a graduated change in stiffness between the limber drill pipe above and the rigid drill collars below. This graduated change in stiffness reduces the likelihood of drill pipe fatigue failures when Heavy-Water drill pipe is run in the critical transition zone of destruction. Performance records complied during the past few years show that running Heavy-Water drill pipe above the drill collars definitely reduces drill pipe fatigue failures. Heavy-Water drill pipes heavy-wall design resist the high-stress concentration. Because of this construction, Heavy-Water drill pipe can be inspected by the same technique used to prevent drill collar failure.
The number of joints of pipe that should be run in the transition zone is important. Based on successful field experience, a minimum of 18 to 21 joints of Heavy-Water drill pipe are recommended between the drill collars and the regular drill pipe in vertical holes. Thirty or more joints are commonly used in directional holes.
Exercise 1.
Vocabulary to be remembered:
drill pipe
drill collar 1. , 2. ()
accumulate [ ] (), ()
fatigue damage
joint 1., 2., 3., , ,
4. (.) ,
stress concentration
bending 1., 2., 3., ,
limb 1. , ; 2.
stiff , , , ,
cyclic ,
pipe whipping (. )
bounce 1., , , 2.
bucking 1., , 2.
to graduate 1., 2.
drill stem 1. ( ),
2. ( )
to comply [ ] ,
run , (. )//
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(. ).
tool joint , .
upset 1. ; 2. ; 3. ; .
Exercise 2.
Answer the following questions:
- Why do many drill pipe failures occur in the drill stem?
- What are two factors that cause extreme bending stress concentration in the bottom joint of drill pipe?
- What do performance records complied during the past few years show?
- How can we prevent drill collar failure?
- How many joints of heavy-water drill pipe are recommended between the drill collars and the regular drill pipe in vertical holes?
- How many joints are used in directional holes?
Exercise 3.
Find the proper Russian equivalents to the given English terms:
- transition 1.
- accelerate 2.
- attribute 3. ,
- cyclic 4.
- pipe whipping 5. ,
- transmit 6. ,
- cumulation 7.
- rigid 8.
- zone of destruction 9. ,
- fatigue damage 10. ,
Exercise 4.
Complete the following sentences.
1.Many drill pipe failures occur 2. Two factors that cause extreme bending stress concentration 3. When drill pipe is subjected 4. Moving these joints 5. Heavy-water drill pipe provides 6. This graduated change in stiffness 7. Performance records complied 8. Because of its construction 9. The number of joints of pipe 10. Based on successful field experience
Exercise 5.
Translate into English.
1. . 2. . 3. ( ) . 4. . 5. , . 6. . 7. .
TOOL JOINTS.
One of the primary purposes of drill pipe is to transmit drilling torque from the rotary table driving kelly bushing to the drilling bit at the bottom of the hole. It also provides a means whereby fluid may be circulated for lubricating and cooling the bit and for the removal of cutting from the well bore.
Drill pipe connections require different treatment than drill collar connections. Drill pipe tool joints are much stiffer and stronger than the tube and seldom experience bending fatigue damage in the connection. Therefore, tool joint connections are normally selected based on tensional strength of the pin connection and tube and not on bending strength ratios as in drill collar connections.
Drill collar connections differ in that they are a sacrificial element and can never be made as strong as the drill collar body. The repair is also different. Cutting off the old connection and completely remachining a new one can renew a drill collar connection; whereas chasing the threads and refacing the shoulder because of its short length can only rework a drill pipe connection. Leaking fluid, careless handling causes the most common damage occurring to drill pipe tool joints, thread wear or galling, and swelled boxes due to outside diameter wear.
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As with drill collars, the break-in of new drill pipe tool joints is extremely important for long life. Newly machined surfaces are more susceptible to galling until they become work hardened. Therefore, the connections should be chemically etched by a gall-resistant coating to hold the thread compound and protect the newly machined surfaces on the initial makeup. Extra care is essential to ensure long and trouble-free service. Thread protectors should be used while drill pipe is being picked up, laid down, moved or stored.
Be sure to thoroughly clean all threads and shoulders of any foreign material or protective coating and inspect for damage before the first makeup. If kerosene, diesel or other liquid is used, some time should be passed before applying thread compound to the connections. When applying compound, be sure to cover thoroughly the entire surface of the threads and shoulders of both pin and box connections. It is preferable to use a good grade of zinc thread compound that contains no more than 0, 3% sulfur. Proper initial makeup is probably the most important factor affecting the life of the tool joint connections.
Exercise 1.
Vocabulary to be remembered:
tool joint ,
torque
rotary table 1. ; 2.
driving kelly bushing
kelly ,
center 1., , 2., 3., 4.
cutting [ ]
pin . ( ), ()
ratio [ ] 1., , ,
2., ,
to chase threads
shoulder 1., , , 2.,
rework ()
to handle -
galling 1. (), 2., 3.
swell , ,
break-in 1., , 2.
susceptible [ ] to
etch [ ] 1., , 2.
coating 1. , 2., 3.
make up (, , )
grade [ ] 1., , , 2.,
.
proper , ; ; ; ; .
Exercise 2.
Answer the following questions:
1.What is the primary purpose of drill pipe?
2.Do drill pipe connections require different treatment than drill collarconnections? Explain why?
3.What should be done to renew a drill collar connection?
4.What is extremely important for long life of drill collars?
5. How can we protect the newly machined surfaces on the initial makeup?
6. When should thread protectors be used?
7. What thread compound is preferable to use and why?
Exercise 3.
Find the proper Russian equivalents to the given English terms:
1. lubricate 1.
2. refacing 2.
3. remachining 3.
4. susceptible 4.
5. coating 5.
6. sufficient 6.
7. thread protectors 7.
8. leaking fluid 8.
9. rotary table 9. ,
10. to chase threads 10.
Exercise 4.
Complete the following sentences:
1. One of the primary purposes of drill pipe is 2. Drill pipe connections require 3. Drill collar connections differ 4. Cutting off the old connection 5. Leaking fluid 6. As with drill collars 7. Extra care is essential 8. If kerosene, diesel or other liquid is used 9. When applying compound 10. Its preferable to use
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Exercise 5.
Translate into English:
1. , . 2. - . 3. , . 4. , . 5. . 6. . 7. .
Unit 3.
