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Патент USA US2111196

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March 15, 1938.`
H. G. TEXTER
2,111,196
WELL CASING JOINT
Filed Feb. 2e, 1935,
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INVENTOR.
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BY ÍÖ/WÍÉ/IAL’CÄÁM#
75;. 'ATTORNEYA’
atented
ar. l5, i3
2,111,196
WELL oasrNG .rorN'r
Howard G. Texter, rI‘ullsa, Ükla., assigner, by
mesne assignments, to The National Supply
Company, Pittsburgh, Pa., a corporation of
Pennsylvania
v Application February 26, 1935, Serial No. 8,278
4 claims.
(ci. 2st-.146i`
The invention relates to oil Well casing formed
of a plurality of lengths of tubes connected end
to-end by threaded joints.
f
In drilling an oil Well'the practice is, as the
5 drilling progresses, to line the hole with casing
:formed of seamless or other types of tubing,
depending, among other things, upon the loca
tion of thecasing and the size of the hole. For
example, a hole of relatively large diameter ma?)7
10 be drilled to_ a depth of 500 feet after which a
string of casing of a suitable relatively large di
ameter is placed in the hole. Thereafter the
drilling of a hole of- a smaller diameter proceeds
f
through and below the ñrst casing until it is
15 necessary or desirable to insert another casing
of smaller diameter than that at the top of
the hole, which procedure is continued until the
well is completely drilled; each string of casing
extending to the top of the well.
'20
>
In setting a string of casing, whether it ex
tends from the topto the bottom or to an in
termediate level in a well, successive lengths of
tubes are connected to each other at the top of
the well- and the casing progressively lowered,
25 the weight of the casing being sustained by the
bodies of the individual tubes and by their con
necting threaded joints. This makes it necessary
to provide joints of substantial strength and
high efficiency. Joint eliiciency, as understood
30 by those skilled in the art, and as hereinafter
used, is the percentage ratio of the ultimate
strength of the joint divided by the ultimate
strength of the connected tubing. Joint strength,
on the other hand, is measured by the actual
35 tensional pull required to produce failure of the
joint. . Joint strength includes ñrst the yield
point of the joint, and second the ultimate
strength of the joint at break.
It is occasionally necessary to pull a string of
casing
from a well by engaging the top of the
40
casing and progressively raising it and unscrew
ing the joints to disassemble the`Í casing as it is
pulled. For this purpose also, it is necessary to
provide joints having substantial' strength be
45 cause some of the joints must sustain the weight
' line of casing is accidentally dropped into a well
which makes it necessary to ñsh it out.
In providing joints for well casing the pre
vailing practice has been to endeavor to make
them as strong as possible, and'in fact as strong Ul
as the tensile strength of the tubes forming the
casing, which would be 100% efficiency. How
ever, this end has not been attained in joints
made according to the standard Well-recognized
speciûcations of the American Petroleum Insti
tute, particularly in joints for larger sizes of
casing, say l0 inches and upwards in diameter.
If a string of casing is provided with joints which
are as strong as the body of the tubing of which
the casing is formed, in the pulling of the string 15
it may break in the body of one of its tube
lengths or at a joint, and in either event a long
string of casing may stretch several hundred
feet over-all, with the bodies of the tubes, or
the joints, or some of them, stretching beyond g
their elastic limit which renders them unsuitable
for future use. If a string of casing breaks from
axial tension in the body of the tube the metal
thereof necks down to such an lextent that it is
diiiicult or impossible to engage the tubing by g
ñshing tools. Thus net_only is the casing lost,
but likewise the Well may have to be abandoned.
The object of my invention is to provide a
string of oil well casing having joints of high
strength but nevertheless of such strength with
relation to that of the tubes of which the casing
is formed that a break in the string will occur
at a joint. '
r In the practice of my invention I provide a
string of oil well casing formed of a plurality of .
tubes connected end-to-end by threaded joints,
each of which is so formed that its ultimate
strength under tension longitudinally of the cas
ing is not less than the yield point ofthe tubes
connected by the joint, and each of which has 40
an ultimate strength materially less than that of
the ultimate strength of its connected tubes. The
words “joint ultimate strength materially less
than the ultimate strength of the tubes” are
meant to deñne that llilmit at which the stress has
exceeded thc’yield point of the tube but not
of casing several thousand feet in length and as caused objectionable or material permanent elon
well as overcoming the frictional resistance be
gation or plastic flow. By thus establishing the
tween the casing and the wall of the drilled ` joint strength with relation to that of the tube
hole. Strings of _casing are frequently so pulled lengths, any break that occurs in the string will 50
50 from a Well when a dry hole is drilled, when a
be _at a joint rather than in the body of a tube
well has run its life and the casing has not been length, but the joints are nevertheless of such
destroyed or impaired by corrosion or otherwise, ‘ strength that none of them breaks before liability
when in the running of a string of casing it sticks of lmpairing their connected tube lengths by
in the well making it necessary to withdraw it stretching the tubes beyond their elastic limit.
55
and drill out the obstruction, and also when a
2
2,111,196
The invention is illustrated in the accompany- ‘ of tubes of diiîerent wall thickness as a matter
ing drawing of which Fig. 1 is a diagrammatic,
cross-sectional view of an ¿oil-well casing pro
gram, and Fig. 2 a longitudinal central sectional
view'of one form of joint that may be used in
the practice of the invention.
of economy, although that is not the prevailing
practice which is to form a string of casing from
tubes of uniform wail thickness. In the latter
event, all of the joints of the casing are of uni
form strength as well as of uniform eñ‘lciency.
By providing a string of casing With joints of
the herein described eiîiciency the advantages of
ing of a plurality of strings _of casing, which may my invention are attained, they being that in
l include an inner string 2 extending from the top ' case the string breaks when it is being pulled 10
to the bottom of the Well, an intermediate string from a Well or under other circumstances, it will
3 of larger diameter extending from the top to break at a joint rather than in the body of one
of its tube lengths which makes it difficult, and
an intermediate level, and a string 4 of still
sometimes impossible to ñsh the remainder of
larger diameter extending from the top to an in
the string from a well. Likewise by making my 15
15 termediate level above that at the bottom of
string 3. Each of the casing strings 2, 3 and 4 is joint eñlciency, throughout each string, approxi
formed of lengths of tubing connected to each mately 85%, rather than a materially higher
other by threaded joints 5,'6 and 'l respectively.V eñìciency, I am able to reduce the outer diam
The joints may be of any particular type so eters of the joints and increase the inner diam
eters with the attending advantages of smaller 20
20 long as their strength and eiìciency is made with
in the limits heretofore described. The joint, starting well diameter while maintaining the
`
disclosed in Patent No. 1,927,656 to Eaton and same bottoming well diameter.
According to _the provisions- of the patent
Burnish, and an improved form thereof disclosed
statutes, I have explained the principle'and mode
in patent application vSerial No. 7,212, ñled Feb
ruary 19, 1935, by George M. Eaton, is capable of operation of my invention, and have illus 25
of being made with high strength and eillciency. trated what I now consider to represent its best
Having reference to Fig. 1, a Well I is shown
as being provided with a casing program consist
I have found that by establishing the proper up
setting, machining and threading operations that
vthe George M. Eaton joint can be made to fulfill
30 the objects of my invention.
A joint of the Eaton type has been illustrated
in Fig. 2 of the drawing and includes threaded
male and female portions Ill and Il formed in
tegrally With the respective tube lengths.
In
35 making the joint, the pipe ends are upset to pro
vide the necessary thickness for strength and
then are machined internally and externally
to exact, desired, concentric diameters. Com
plernentary, sturdy, trapezoidal threads, and also
40 sealing surfaces, if desired, are the'n machined on
the male and female members with the taper of
the threads being relatively steep and with a
relatively small number of threads per inch.
The threads are preferably formed with ñat
45 crests and roots parallel to the axis of the jointlv
While the joint strength may vary within the
limitation that the ultimate strength of the joint
is not less than the yield point of its adjoining
tubes, and is materially less than the ultimate
50 strength of such tubes, the ef?ciency of each
joint is preferably about 85%.
It should be ap
' preciated that the particular strength of each
joint is related to that of the tubing tensile
strength which, of course, varies with the size
and wall thickness of the tubing. Thus if in a
embodiment.
However, I desire to have it un
derstood that ’Within the scope of the appended
claims vthe invention may be practiced otherwise
30
than as specifically illustrated and described.
I claim:
.
1. A string of oil-well casing formed of a plu
rality of tubes connected end-to-end by threadedl
joints, each joint being formed to have an ef
35
ñciency of about 85 per cent.2. An oil-well casing program comprising a
plurality of nested Strings of casing, the joints
of said strings being formed to have a uniform
efficiency throughout the program and each joint
being formed to have an ultimate strength not 40
less than the yield point of the casing joined
thereby but being materially less than the ulti
mate strength of such casing, whereby in case
any string breaks the break will occur at a joint
prior to material elongation of the string.
45
3. A string of oil-well casing formed of a plu
rality of tubes connected end to end by threaded
joints, the joints in at least the upper portion
of the casing being formed to have an efliclency
of about 85 per cent.
,
50
4. An oil-well casing program comprising a
plurality of nested strings of casing, the joints
of at least two of said strings being formed to
Vhave a substantially uniform eiliciency through
out the program and each joint being formed to 55
particular string of'vcasing of uniform internal
have an ultimate strength not less than the yield A
diameter, the Wall thickness of the tubes at the
mid length of the string is less than those at the
upper end, the strength of the joints connecting
point of the casing joined thereby but being m'a
60 the thinner walled tubes is less than that con
necting the thicker walled tubes at the top 0f the
string. However the joints are still of uniform
efîiciency. A string of casing may be thus formed
terially less than the ultimate strength of such
casing, whereby in case any string breaks the
break will occur at a joint prior to material 60
elongation of the string.~
HOWARD G.
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