US 2971373 A
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Description (OCR text may contain errors)
Feb. 14, 1961 A. P. HELDENBRAND 2,971,373
METHOD FOR MINIMIZING DRILL PIPE FAILURES Filed July 5, 1957 INVENTOR. A. I? HELDEN/SEA/VD ATTORNEY United States Patent METHOD non MINIMIZING DRILL PIPE FAILURES Arthur P. Heldenhrand, SE. 35th, Oklahoma City, Okla.
Filed July 5, 1957, Ser. No. 670,069
5 Claims. (Cl. 73-99) This invention relates to an improved method and apparatus for minimizing failures of drill pipe of the type used in rotary drilling of oil and gas wells.
As it is well known in the oil and gas well drilling industry, drill pipe appearing to be in perfect condition often fails during a drilling operation, resulting in an expensive and time consuming fishing job to recover the lost portion of the drill string. Many testing devices have been designed to test the pipe for hidden defects between drilling runs while the pipe is on the surface of the ground. The majority of these testing devices rely upon the magnetic properties of the drill pipe and are effective only in locating severe pits or cracks in the drill pipe. Such testing devices do not indicate the presence of localized stress areas in the drill pipe, nor the minimum tension (either lengthwise or in torque) which the drill pipe will stand. Therefore, drill pipe which has been tested for cracks and corrosion will still frequently fail during a drilling operation.
It is a generally accepted theory that the joints in a drill string which will withstand the least tension, in either a longitudinal direction or in torque, will receive the major portion of the vibration and twisting of the drill string and fail prior to failure of the other joints. Heretofore, however, this theory has not been fully used in the field to anticipate drill pipe failures. It is known to place each joint of a drill string under longitudinal tension prior to running the pipe in a well to determine whether the pipe meets the minimum tension requirements promulgated by API and the various drill pipe manufacturers. However, this method is ordinarily used only after the pipe has been run through at least one drilling operation, and the method does not necessarily give an indication of the torque which the drill pipe will withstand. When analyzed, it will be appreciated that a joint of drill pipe permanently twisted, either intentionally or through use in a drilling operation, will have localized stress areas which are likely to cause a failure of the pipe during a subsequent drilling operation. It should also be noted that although the majority of drill pipe failures occur after the pipe has been in service for a period of time, some failures occur during the first use of the drill pipe. Therefore, new drill pipe does not always meet the minimum tension requirements for the intended use, even though the walls of the drill pipe are not corroded or cracked in any manner.
The present invention contemplates a novel method of checking the drill pipe before and after it is run in a well to anticipate drill failures. In its broader aspects, this invention contemplates the determination of the amount of twist permanently induced in each joint of a string of drill pipe occurring through use of the pipe, whereby those joints having localized stress areas and which will be the most likely to fail may be discarded. I also contemplate tensile testing the drill pipe prior to running the drill pipe in a well to minimize failures of the drill pipe during the initial use thereof. Further- "ice more, this invention contemplates novel apparatus for determining the permanent twist of drill pipe.
An important object of this invention is to minimize drill pipe failures and increase the economy of oil and gas well drilling operations.
Another object of this invention is to provide a novel method of locating those joints in a drilling string which have localized stress areas and which will be the most likely to fail during a subsequent drilling operation.
A further object of this invention is to determine the permanent twist induced in drill pipe during use of the pipe in a drilling operation. In conjunction with this objective, it is also an object of this invention to determine those joints of drill pipe which do not meet the calculated minimum tensile strength requirements for the pipe.
Another object of this invention is to provide simple and economical apparatus for determining the permanent twist of a joint of drill pipe.
Other objects and advantages of the invention will be evident from the following detailed description, when read in conjunction with the accompanying drawings which illustrate my invention.
In the drawings:
Figure 1 is a longitudinal sectional view, partially in elevation, of a point of drill pipe having a sighting device on one end thereof and a target device on the opposite end thereof.
Figure 2 is an enlarged cross sectional view of the punching mechanism used for marking the ends of a joint of drill pipe.
Figure 3 is an enlarged plan view of a portion of the target device of this invention.
Referring to the drawings in detail, reference character 4 designates a typical joint of drill pipe having an internally threaded box 6 on one end thereof and an externally threaded pin 8 on the opposite end thereof. It is to be understood that the specific design of the drill pipe 4 is immaterial, so far as the present invention is concerned. A sighting device, generally indicated at 10, is secured in the box 6 of the pipe 4; and a target device, generally indicated at 12, is secured on the pin 8 of the pipe. During testing of the pipe 4, the pipe will be supported in a substantially horizontal position by any suitable supporting mechanism (not shown).
The sighting device 10 comprises an externally threaded tubular member 14 of a size to be threaded into the box 6. A circumferential flange 16 is formed on the outer end of the member 14 to abut the outer end of the box 6 when the member 14 has been completely threaded into the box. The outer end of the member 14 is suitably machined to provide a circumferential shoulder 18 which receives a complementary shoulder of a tubular mandrel 20. It will be understood that the shoulder 18 aligns the mandrel 20 with the member 14, whereby the longitudinal axis of the mandrel 20 will be aligned with the longitudinal axis of the drill pipe 4. Apertured plates 22 are secured in the inner end of the member 14 and the outer end of the mandrel 20 to receive a suitable rod 24 and secure the mandrel 2t) rigidly on the shoulder 18 of the member 14.
The outer periphery of the mandrel 20 is machined smooth to slidingly receive a sleeve 26, with the sleeve 26 preferably being of a size to provide a friction fit on the mandrel 20, whereby the sleeve 26 will tend to stay in any angular position on the mandrel 20 in which it is placed. A suitable retaining ring 28 is threaded onto the outer end of the mandrel 20 to secure the sleeve 26 lengthwise on the mandrel against a circumferential shoulder 30 at the inner end of the mandrel.
A tube or pipe 32 is secured on the outer periphery of the sleeve 26 by means of a suitable pad 34, with 3 the tube 32 extending radially from the sleeve 26. The pad 34 may be secured to the outer periphery of the sleeve 26 in any suitable manner, such as by bolts, and the tube 32 is preferably welded to the pad 34. A tapered block 36 is secured in the inner end of the tube 32 to mate with the tapered inner end of a telescope support rod 38 which is telescoped into the outer end of the tube 32, whereby the support rod 38 is held in the tube 32 in a fixed angular position. A telescope 40 is supported by a bracket 42 on the outer end of the rod 38 in such a position that the telescope 40 extends parallel with the longitudinal axis of the pipe 4. The bracket 42 may be of any desired construction to permit adjustment of the telescope 40, but preferably is constructed so that the telescope 40 can be secured in a fixed position on the rod 38, whereby the telescope will be truly parallel with the longitudinal axis of the pipe 4. The rod 38 may be additionally held in the tube 32 by means of a set screw 44 threaded through the wall of the tube 32, if desired.
Another tube or pipe 46 is secured to the tube 32 in such a manner as to extend substantially parallel with the telescope 40 and the longitudinal axis of the pipe 4 and is utilized to receive a support arm 48 of a punch holding mechanism 50. The tube 46 may be welded to the tube 32 to make a rigid connection, and the arm 48 may be secured in the tube 46 by a suitable set screw 52.
The punch holding mechanism 50 (see Fig. 2) comprises a hollow housing 54 having a bottom wall 56 and open at its upper end. A bushing 58 is slidingly disposed in the housing 54 and issuitably bored to receive the upper enlarged portion of a center punch 60. The punch 60 extends downwardly from bushing 58 through an aperture 62 in the bottom wall 56 of the housin 54. A button-like member 64 is threaded into the upper end of the bushing 58 to hold the center punch 60 in the desired position in the bushing and to form a striking area for hand operation of the punch 60, as will be more fully hereinafter set forth. The bushing 58 and punch 60 are continually urged upwardly in the housing 54 by a suitable helical compression spring 66 anchored between the bottom wall 56 and the lower end of the bushing 58. A handle 68 extends transversely out from the bushing 58 through a C-shaped slot 70 in one side of the housing 54. It will be apparent (see also Fig. 1) that when the handle 68 is in the lower horizontal leg of the slot 70, the center punch 60 will protrude below the bottom wall 56 of the housing 54; whereas when the handle 68 is in the upper horizontal leg of the slot 70, the center punch 60 will be contained wholly within the housing 54. When the handle 68 is in the vertical leg of the slot 78, the bushing 58 and center punch 60 may be moved up and down to alternately extend and retract the center punch 60.
From the foregoing it will be apparent that the sighting device it) is mounted in the box 6 of the pipe 4 and is constructed in such a manner that the telescope 40 extends parallel with the longitudinal axis of the pipe 4. The supporting sleeve 26 may be turned on the mandrel 20 to move the telescope 40 around the axis of the pipe 4 for positioning the telescope 40 in the desired angular position. The punch holding mechanism 58 is supported on the instrument supporting sleeve 26 insuch a position that the center punch 60 is preferably in line with the telescope 40 and the longitudinal axis of the pipe 4.
The target device 12 comprises an internally threaded member 74 of a size to be threaded onto the pin end 8 of the pipe 4. An outwardly facing circumferential shoulder '76 is machined on the outer end of the member 74 to receive the inner end of a tubular mandrel 78. The inner diameter of the mandrel 78 is such to provide a snug fit of the mandrel on the shoulder 76, whereby the mandrel 78 will be aligned with the longitudinal axis of the pipe 4. Apertured plates 80 are secured in the outer end of the member 74 and the outer end of the mandrel 78 to receive a suitable bolt 82, whereby the mandrel 78 will be rigidly secured on the member 74.
The outer periphery of the mandrel 78 is machined smooth to receive an inner support sleeve 84. Another support sleeve 86 is telescoped over the inner sleeve '84, with the fit of the sleeve 84 on the mandrel 78 and the fit of the sleeve 86 on the sleeve 84 being such that the sleeves 84 and 86 will be retained in their relative angular positions by friction, yet the sleeves 84 and 86 may be turned by hand. The inner end of the sleeve 84 has a outwardly extending flange 88 thereon which abuts an outwardly extending flange 90 formed on the inner end of the mandrel 78. A suitable retaining ring 92 is threaded onto the outer end of the mandrel 78 to retain the sleeves 84 and 86 in the desired longitudinal positions on the mandrel.
A tube 94 is secured on the flange 88 of the inner support sleeve 84 by means of a suitable bolt 96. The bolt 96 is threaded into the flange 88 to retain the tube 94 in a radial position with respect to the sleeve 84, and, of course, the tube 94 will be turned about the axis of the pipe 4 upon rotation of the sleeve 84. Another tube 98 is secured in a horizontal position on the tube 94 to receive and support another punch holding mechanism 50 of the type previously described. The enter punch 60 of the respective punch holding mechanism 50 will be retained in line with the tube 94 and the longi tudinal axis of the drill pipe 4. a
A target supporting tube 100 is secured in a radial direction on the outer periphery of the outer support sleeve 86 by means of a suitable pad 102. The base portion 104 of a target 106 is telescoped into the tube 100 to support the target radially with respect to the sleeve 86 and the pipe 4. It will 'be understood that the target 186 will be rotated about the axis of the pipe 4 upon turning of the sleeve 86 on the inner sleeve 84, or upon turning of both sleeves 84 and 86. Support rod 104 may be secured in the tube 100 by a suitable set screw 108 to prevent the target 106 from falling out of the tube 100.
As shown most clearly in Fig. 3, a latch 110 is pivotally secured by brackets 112 on the target supporting tube 100, whereby the latch 110 will pivot radially with respect to the sleeves 84 and 86 and extend toward the tube 94 mounted on the inner sleeve 84. The outer end 114 of the latch 110 is suitably designed, such as being bifurcated, to extend around the tube 94 when the latch is in a horizontal position, whereby the sleeves 86 and 84 will be locked together for simultaneous movement on the mandrel 78. A suitable stop (not shown) will be provided on the tube 94 or in the bracket 112 to limit the downward movement of the latch 110 and retain the latch in a horizontal position as shown in Fig. 1. However, the latch 110 may be swung upwardly, or outwardly, oif of the tube 94 to unlock the sleeves 84 and 86 for separate movement thereof.
As also shown in Fig. 3, degree markings 116 are provided on the inner end of the outer supporting sleeve 86, and a suitable zero marking (not shown) is provided 1 on the flange 88 of the inner sleeve 84, whereby the relative positions of the sleeves 84 and 86 may be determined. The markings 116 are arranged in such a manner that the zero degree mark on the sleeve 86 will be aligned with the zero marking on the flange 88 of the inner sleeve 84 when the latch 100 is connected with the tube 94. In this position of the target device, the respective punch 60 will be in line with the axis of the pipe 4 and a suitable vertical line (not shown) provided in the center of the target 106.
In practicing the method of this invention, I prefer to place each joint of a string of new drill pipe under tension along its longitudinal axis. Such a tensioning operation maybe performed by use of a tension machine as disclosed in my United States Patent No. 2,757,536. Basically, each joint is placed under tension by threading pulling members on the opposite ends of the joint and then forcing the pulling members apart. According to the method of the present invention, each joint of a string of drill pipe is placed under tension to its actual minimum yield point, and such information is suitably recorded. Each joint will, of course, be marked with a suitable identifying number or symbol so that each joint can be later identified with its original tensile strength. Those joints which begin to yield before the force exerted equals the minimum yield strength specified by API (that is, those joints not meeting API tensile strength requirements) should be eliminated and not used in the drill string. Those joints meeting or exceeding API specifications are used in the drill string. The fact that some joints exceed API specifications merely indicates that they are made out of better steel. In each instance, the actual tensile strength of each joint is recorded, as indicated above.
Following the tensioning of the drill pipe, the sighting device and the target device 12 are secured on the opposite ends of one of the joints of drill pipe, in the manner illustrated in Fig. l. The latch 110 of the target device 12 is secured on the supporting tube 94 of the respective punch holding mechanism 50 to align the target 106 with the respective punch 60. Also, the handle 68 of each punch holding mechanism 50 is moved into the upper horizontal leg of the respective slot 70 to retain the punches 60 in the housings 54 out of contact with the pipe 4. The support sleeves 84 and 86 are then moved on the mandrel 78 until the target 106 is aligned with the telescope 40. It will be understood that one operator watches through the telescope 40 while another operator turns the sleeves 84 and 86. When the target and telescope are aligned, the handle 68 of each punch holding mechanism 50 is turned into the vertical portion of the respective slot 70; whereupon an operator strikes the button 64 of each punch mechanism to drive the inner ends of the punches 60 into the outer periphery of the pipe 4 and provide an indentation in each end portion of the pipe. Since the punches 60 are aligned with the telescope 40 and the target 106, the indentations made by the punches will be aligned with the axis of the pipe 4. The handle 68 of each punch mechanism is then again moved back into the upper horizontal leg of the respective slot 70, and the sighting device 10 and target de vice 12 are detached from the joint 4. This operation is repeated for each joint of the drill pipe to be run into a well through a drilling operation. If desired, a circular indentation (not shown) may be punched into the pipe 4 around each of the indentations made by the punches 60 to facilitate subsequent location of the markings.
In addition to tensioning and placing aligned marks on each joint of the drill pipe, I also prefer that the length of each joint of the drill pipe be measured, and such information suitably recorded along with the actual tensile strength of each joint. The joints of drill pipe are then run in a well in tandem relation in the usual manner through a drilling operation.
Upon removal of the drill pipe from the well, each joint is disconnected from the drill string, and the sighting device 10 and target device 12 are again attached to a joint in the manner shown in Fig. 1. Upon assembly of the sighting device 10 in the box 6 of the joint 4, the support sleeve 26 is turned on the mandrel 20 until the respective punch 60 is directly opposite the indentation previously made in the pipe 4. When locating the indentation, the respective handle 68 is turned into the vertical portion of the respective slot 70 and the center punch 60 held into contact with the outer periphery of the pipe. When the center punch is seated in the indentation, the respective handle 68 is moved into the lower horizontal leg of the respective slot 70 to hold the center punch in the indentation and align the telescope 40 in the same position it was when the indentation was made.
Upon assembly of the target device 12 on the pin 8 of the joint 4, the inner sleeve 84 is turned on the mandrel 78 until the respective punch 60 is aligned with the respective indentation in the pipe. The handle 68 is then moved into the lower horizontal leg portion of the slot 70 to hold the center punch 6t) in the indentation. The latch is then disengaged from the tube 94 and the sleeve 86 is turned on the sleeve 84 until the target 106 is aligned with the telescope 4-0. Whereupon, the relation of the markings 116 on the sleeve 86 with respect to the zero marking on the inner sleeve 84 Will indicate the amount of permanent twist induced in the pipe 4 by the drilling operation.
When such measurement is completed, the punches 60 are retracted into housings 54 and locked into position by the handles 68, and the sleeves 84 and 86 are aligned, with the latch 110 again engaged with the tube 94. These operations are repeated on each joint of the drill pipe removed from the well, whereby the permanent twist of each joint of drill pipe will be determined. Those joints having been twisted a substantial degree will have localized stress areas which make the joints likely to fail in a subsequent drilling operation; whereas those joints having negligible twist will be in substantially the same condition as prior to the first drilling operation and will be suitable for subsequent use. It will be understood that the permissible twist which may be induced in a joint of drill pipe will be dependent on the materials of construction, size of the pipe and many other factors. Therefore, at this state of the art, no maximum tolerable permanent twist can be specified for all drill pipe used. As a practical matter, those joints of drill pipe permanently twisted a substantially greater amount than the other joints of a drill string should be discarded and not reused in a drilling operation. Generally speaking, the ten percent of the joints having the highest permanent twist will be the most likely to fail and should be discarded prior to further drilling.
When the drill pipe is removed from a well, the length of each joint should also be measured and compared with the length of the joint prior to the drilling operation. Those joints which have been stretched through use in the well will undoubtedly take the major portion of the stretch of the drill string during a subsequent drilling operation. Therefore, those joints which were permanently stretched by the first drilling operation would be likely to fail during a subsequent operation and should be discarded.
As further assurance that the drill pipe will not fail in a subsequent drilling operation, each joint is preferably again placed under longitudinal tension in the manner previously described. Each joint is placed under tension to its actual minimum yield point, and the result obtained is compared with the original tensile strength of the joint. Those joints which do not meet the minimum API tension specifications are discarded as before, since such joints would take the majority of the vibration and tension of the drill string and be the most likely to fail. When a used joint of drill pipe does not meet the minimum longitudinal tension requirements, it usually indicates that the joint is worn on its outer surface or corroded through use.
The changes in tensile strength of drill pipe will vary with drilling conditions, but I have found that the variations usually follow a pattern, with the normal variations in a localized area being fairly uniform. In some areas, such as West Texas, when wear or corrosion does not take place, drill pipe is work-hardened through use, and the tensile strength of each joint measurably increases through use. However, when excessive workhardening occurs, the drill pipe becomes brittle and is likely to fail, particularly if subjected to rather sudden blows or shocks. Therefore, I prefer to discard those joints wherein the tensile strength has been raised more than twenty percent through use. Those joints having substantially the same, or an increase of twenty percent or less in tensile strength, may be re-used in a drilling operation with a minimum risk of failure.
In other areas, such as in Kansas, the tensile strength of drill pipe will decrease slightly, even though the pipe is not worn or corroded. In these areas, the drill pipe should be removed from the drill string when its actual minimum tensile strength decreases more than five percent from the original tensile strength. Thus, in any area, the drill pipe should be removed from the drill string when its minimum tensile strength increases more than twenty percent or decreases more than five percent from its original tensile strength. It is to be understood that the time the pipe has been in service and the amount of footage the pipe has drilled are of no consequence in determining the suitability of the pipe. If the pipe is placed in use and the tensile strength changes more than specified above, it should be removed from the drill string.
From the foregoing it will be apparent that the present invention provides a novel method and apparatus for minimizing drill pipe failures. The method may be practiced on drill pipe at any stage of a well drilling operation. The method gives evidence of localized stress areas in drill pipe induced through use of the drill pipe, whereby those joints most likely to fail during a subsequent drilling operation may be identified and discarded or removed from the drill string. Also, experience has shown that new drill pipe having the prescribed longitudinal tension, as described above, will ordinarily be suitable for use in at least one drilling operation, with a minimum likelihood of failure of the pipe. It will further be apparent that the present invention provides a novel apparatus for placing aligned marks on the opposite end portions of joints of pipe and for determining the amount of permanent twist induced in a joint of drill pipe.
Changes may be made in the combination and arrangement of parts or elements and steps or procedures heretofore set forth in the specification and shown in the drawings without departing from the spirit and scope of the invention as defined in the following claims.
1. A method of minimizing failures of drill pipe, comprising the steps of:
(a) placing aligned marks on the opposite ends of each joint of the drill pipe,
(12) running the drill pipe in a well through a drilling operation,
removing the drill pipe from the well and disconnecting each joint,
(d) measuring the angular displacement of said marks to determine the amount of permanent twist in eachjoint resulting from the drilling operation, and
(e) discarding those joints having the largest permanent twist.
2. A method of minimizing failures of drill pipe, comprising the steps of:
(a) tensioning each joint of the drill pipe to its actual minimum yield point,
(b) discarding those joints not meeting minimum yield strength requirements,
(0) measuring the length of each joint,
(d) placing aligned marks on the opposite ends of each joint,
(e) running the marked joints in a well drilling op eration,
(f) removing the drill pipe from the well,
(g) measuring the length of each joint removed and the angular displacement between said marks, and
(h) discarding those joints either permanently stretched or twisted.
3. A method as defined in claim 2 characterized further in that each joint removed from the well is again tensioned to its actual minimum yield point, discarding those joints not meeting minimum yield strength requirements by said second tensioning, and discarding those joints wherein the minimum yield strength has increased more than twenty percent or decreased more than five percent from the strength thereof determined by the firstmentioned tensioning.
4. A method as defined in claim 1 characterized further in that said marks are placed on each joint by mounting a sighting device on one end of the joint and a target device on the opposite end of the joint, aligning the sighting and target devices, and punching an indentation in the outer periphery of the joint adjacent each end of the joint on the line of the sighting and target devices.
5. A method as defined in claim 4 characterized further in that the angular displacement of said indentations is measured by mounting the sighting and target devices on the opposite ends of the joint, with each device aligned with the indentation adjacent thereto, then turning the target device until the devices are aligned, and measuring the degrees the target device was turned.
References Cited in the file of this patent UNITED STATES PATENTS 958,736 Ferris May 24, 1910 11,667,995 Steinle May '1, 1928 2,673,613 Irwin Mar. 30, 1954 2,712,756 Greer et al. July 12, 1955