Патент USA US2111196код для вставки
March 15, 1938.` H. G. TEXTER 2,111,196 WELL CASING JOINT Filed Feb. 2e, 1935, .2., MHTI.@ l l l l I I INVENTOR. I I I I I 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.