drill collars

Aug 14th, 2016
Studypool Tutor
Price: $5 USD

Tutor description

Word Count: 2658
Showing Page: 1/14
Drill CollarsIn the early years of rotary drilling , a typical bottomhole assembly (BHA) consisted of nothing more than a shortcrossover sub, or collar, between the bit and the drill pipe. Over time, drillers observed that penetration rates tendedto increase as more weight was applied to the bit,and so they began using BHAs with longer sections of heavy pipe(in keeping with the original terminology, these heavy joints of pipe have continued to be called drill collars).But even as these heavier BHAs brought improved bit performance, it became clear that applying more weight to thebit involved a trade-off: a greater potential for drill pipe failure due to increased compressive force and resultantbending or buckling.When drill pipe rotates in a compressed state, it experiences cyclic stress reversals. Each rotation of the stringcauses the drill pipe fibers to go from compression to tension to compression. This high cyclic stress bending causesmetal fatigue, which is cumulative and eventually leads to drill pipe failure ( Figure 1 ).Figure 1Buckling tendencies are greatest in the pipe body between the end upsets, which is the thinnest and most flexiblepart of the drill string. The abrupt change in cross-sectional area between the pipe body and the upsets sets up stressconcentrations just above and below the much stiffer tool joint.Thus, a fundamental objective in BHA design and drill collar weight selection is to "eliminate the potential for axial andtorsional b

Review from student

Studypool Student
" Excellent job "
Ask your homework questions. Receive quality answers!

Type your question here (or upload an image)

1827 tutors are online

Brown University





1271 Tutors

California Institute of Technology




2131 Tutors

Carnegie Mellon University




982 Tutors

Columbia University





1256 Tutors

Dartmouth University





2113 Tutors

Emory University





2279 Tutors

Harvard University





599 Tutors

Massachusetts Institute of Technology



2319 Tutors

New York University





1645 Tutors

Notre Dam University





1911 Tutors

Oklahoma University





2122 Tutors

Pennsylvania State University





932 Tutors

Princeton University





1211 Tutors

Stanford University





983 Tutors

University of California





1282 Tutors

Oxford University





123 Tutors

Yale University





2325 Tutors