US 2117357 A
Description (OCR text may contain errors)
May 17, 1938. B. l.. PETERSON 2,117,357
WELL DRILL PIPE Filed Jan. 29, 1937 ATTOR N EYS Patented May 17,1938
PATENT FFICE WELL DRILL PIPE Bert L. Peterson, Wooster, Ohio Continuation of application Serial No. 82,464, May 29, i936. This application January 29,
1937, Serial No. 123,020
(Cl. 28E- 146) 4 Claims.
.10 sections joined together at their extremities by means of threaded couplings, the bending stresses tend to localize at the joints, since the threaded connections are inherently weaker than the body portions of the pipe sections intermediate the 15 connections. This concentration of the bending in the pipe at the couplings and joints has a tendency to injure the threads, and in some instances even causes them to fail completely so that the lower portion of the drill pipe or tool .20 may be lost in the well, necessitating its being fished out.
In the past it has been sought to overcome the tendency of bends in the well drill pipe to injure the threaded joints by providing substan- 25 tially nonflexible couplings and joints of relatively thick wall sections as compared with the drill pipe. The great rigidity of such joints and couplings apparently results in increased localizing of the bending stresses at the mating threads,
.3.0 and does not materially eliminate the injurious effects caused by bends in the pipe.
The injury to the threaded connections which may be said to be caused by bending in the well drill pipe is sometimes increased by mud cut- 35 ting. According to established practice in drilling wells a drilling liquid or mud is forced to the bottom of the well through the tool or drill pipe, and after passing out the bottom thereof is forced up the outside of the tool or pipe and 40 `inside the well casing in order to carry the cuttings from the drilling operation to the top of the well for removal. The liquid or mud is recirculated through the system, and in its passage through the well drill pipe is necessarily 45 maintained under considerable pressure. Consequently, if the bending in the pipe causes any opening or separation between the `threads of the coupling members or tool joints, the mud is forced into such openings and between the 50threads. This mud `is extremely corrosive and `abrasive because of small particles of cuttings and the like carried in suspension. With a prolonged drilling operation with the pipe full of the cuttings so as to cause openings between the 5,5 threads, the Amud gradually eats away portions of the threads to cause ultimate failure of the joint or coupling.
The present application is a continuation of my application Serial No. 82,464, filed May 29, 1936. `In that application I disclosed a Well drill 5 tool joint particularly adapted to join successive stands of a well drill tool pipe together. Each stand of such well drill pipe is, however, composed of a plurality of sections of pipe which are preferably secured together by threaded couplings. It has been found that bending of the well drill pipe during operation causes stresses which appear to concentrate at all the threaded connections so that the deleterious effect of this bending is encountered not only at the joints connecting the successive stands of the drill pipe but also at the couplings which join the pipe sections comprising each stand of the well drill p1pe.
It is, therefore, an object of the present in- .20 vention to provide for use in a rotary well drill pipe or tool flexible joints and couplings for securing the sections of pipe together, so that such couplings and joints have sufficient inherent flexibility to reduce the stresses on the mating threads holding the drill pipe together and thereby reduce thread failures, and the resilient Wabbling and separation of the pipe sections during use.
A more specific object is to provide such joints ,30 and couplings provided with relatively fiexible portions intermediate the ends thereof, which flexible portions are arranged to flex under bending strains in a drill pipe.
A further object is to provide in such well drill joints and couplings increased flexibility in the Zone that is provided for Wrench engagement.
The present invention may be embodied in a well drill pipe joint or coupling construction having the mean diameter of its body portion reduced with respect to the mean diameter of the `drill pipe with which such joints and couplings coupling positioned between and securing the ends of drill pipe sections;
Fig. 3 is a section taken on the line 3-3 of Fig. 2; and
Fig. 4 is a longitudinal sectional view of a modified form of drill pipe coupling.
Referring to the drawing by numerals of reference which are used to designate like parts in each of the several views, the well drill pipe joint illustrated in Fig. l is seen to comprise a pair of tool joint parts I and 20. The joint part I0 is provided with a pin end portion II arranged to engage a box-threaded end portionv 2I of the joint part 20. Preferably threads I3, to connect the joint parts I0 and 2li, are formed with a substantial taper in accordance with well known well drill pipe joint constructions in order to facilitate the breaking of the joint, and the reassembly thereof. The end I2 of the joint part II) opposite the pin-threaded end I I is provided with a socket to engage an end of a section of well drill pipe 3l) by means of threads 33. Preferably the ends 3l of the well drill pipe sections 3U are upset and thickened, as shown, to provide reinforcement for the threads 33 and insure a relatively strong and rigid connection, as well known in the art.
In a similar manner the end of the joint part 20 opposite the box 2i is provided with a socket 22 to receive an upset end 3l of another well drill pipe 33 secured thereto by means of threads 33.
Intermediate the socket end I2 and the pin end II body portion I 4 of joint part II! is formed with a reduced diameter with respect to the diameter of the well drill pipe 3). Likewise body portion 24 of the joint part 20 intermediate the box end 2| and socket end 22 thereof is of reduced diameter with respect to the diameter of the well drill pipe 33.
In forming the body portions I4 and 24 so as to provide therein sections of reduced diameter with respect to the diameter of the Well drill pipe 3D, regard must be had to both the outside diameter A and inside diameter B of such body portions. For example, the body portion I4 of the joint part Ill has an outside diameter A and an inside diameter B. If the outside diameter A and inside diameter B are added together and divided by 2 substantially the mean effective diameter C of the body portion I4 is determined. In this connection, it is to be understood that by mean diameter is meant that diameter denning a circumference at which, if all the metal of the cross-section were uniformly concentrated, the resistance to bending would be substantially equal to the actual resistance to bending at the particular cross-section.
The body portion 32 of the well drill pipe 30 also has an outside diameter D, inside diameter E, and mean effective diameter F determined by dividing the sum of the diameters D and E by 2. The outside diameter A of the body portion of the joint parts is less than the outside diameter D of the well drill pipe and the inside diameter B is less than the inside diameter E of the well drill pipe. Because of the relationship between the cross-sectional areas of the body portions of the joint parts and the body portions of the drill pipe the mean effective diameter C of the joint part is less than the mean diameter F of the drill pipe.
If desired, to obtain increased flexibility and resiliency, the outside diameter A of the body portion of the joint may be made less than the inside diameter E of the well drill pipe, it being understood that the greater the reduction in mean diameter of the body portions of the joint parts the greater will be their inherent flexibility and resiliency. The reduction of the internal diameter B of the body portion of the joint part may be relatively greater than the reduction in outside diameter A of such portion so that the thickness of the wall of the body portion of the joint is maintained at least equal to or preferably thicker than the wall of the body portion 32 of the pipe section 30. Thus, by suitable regulation of the diameters, the resistance of the body portion of the joint or coupling to bending strains may be regulated relative to the resistance of the body portion of the pipe sections. However, in the commercial manufacture of joints and couplings in accordance with the present invention, it is desirable that in forming the joint parts the cross-sectional area of the body portions of reduced diameter is preferably maintained substantially equal to the cross-sectional area of the body portion 32 of the well drill pipe. In this manner the tensile strength of the body portions of the joint parts is not reduced with respect to the tensile strength of the pipe sections. However, due to the reduction in mean diameter of the body portions of the joint parts the resistance to bending thereof is substantially less than that of like lengths of well drill pipe. Accordingly, any bending strains imposed on the pipe during the drilling of a well will tend to deform the body portions of the joint parts and relieve such strains which would otherwise be apt to cause excessive stresses in the threads I3 and 33.
By increasing the lengths of the body portions of reduced diameter I4 and 24 the flexibility and resiliency of the joint parts is likewise increased. It is, however, undesirable to have such body portions of excessive length because of commercial limitations in the manufacture thereof. Ac-
cordingly, it is proposed to form each of the body portions of reduced effective mean diameter of a length substantially greater than the outside diameter A of the reduced diameter body portion. An effective and desirable length is one substantially twice that of the outside diameter A, as clearly shown in the reduced diameter body portion 24 of the joint part 20.
Satisfactory results have been obtained by the use of body portions of reduced diameter which are slightly longer than the internal diameter of such body portions an-d the present invention may include such short body portions, although the longer body portions are more desirable.
In order to facilitate the breaking and assembly of the joint it is desirable to provide means for engaging the joint parts with suitable wrenches. The outside surface 25 of the box end 2I serves as a suitable seat for a wrench to engage the joint part 20. The joint part Ill, however, which has the pin-threaded end II positioned within the box end 2| of joint part 20 is provided with a plurality of wrench lands I5 which are formed circumferentially about the reduced diameter body portion I4 adjacent the pin end II and spaced from one another and the enlarged pin end by annular grooves I 6. The outside diameter of the wrench lands I5 is desirably equal to the outside diameter of the box 2l so that the wrenches used in connection with the well drill pipe may be interchangeably applied to the joint parts IIJ and 20. ends I2 and 22 of the respective joint parts similarly have an outside diameter which is equal to that of the box end 2l sol that they may likewise The socket 'ai liest be engaged by the same size wrenches as engage the box end 2l and wrench lands I5. The wrench lands I5, because of being separated and relatively thin, do not materially strengthen the body portion I4 of the joint part against bending 4strains so that the lands do not objectionably interfere with the eiectiveness of such body portion to absorb such strains. It is desirable that the mean diameter C of the body portions of reduced diameter be substantially uniform throughout substantially the entire length of such body portions in order that the flexing thereof shall be substantially uniform. It is tobe understood, however, that the invention may be practiced by forming the body portion of reduced diameter having a varying mean diameter.
As previously mentioned in drilling a well, it is often necessary to remove and replace the well drill pipe in the casing a number of times before the well is completed. It is customary to assemble a well drill pipe in stands. Each stand includes several lengths or sections of well drill pipe, each section being 20 or 30 feet long. In removal of the well drill pipe from the Well casing, the usual practice is to withdraw from the well several sections of pipe comprising one stand, break the Vjoint between sections and withdraw another stand. Thus a plurality of stands are successively withdrawn from the casing and disconnected from the remaining stands. Accordingly, in the well drilling process some of the joints or couplings will be disconnecteda number of times, whereas others, such as those connecting the several sections of a single stand are rarely disconnected.
lThe well drill pipe joint, as described above and illustrated in Fig. 1 of the drawing, is such as may be desirably applied to connect successive stands. It is, however, desirable that bending strains which occur intermediate the ends of a single stand of pipe be absorbed by a flexible and resilient element in order to minimize stresses which would otherwise be apt to cause failure of the threaded connections securing the several sections of a single stand together.
The present invention contemplates a suitable coupling to relieve the strains at the threaded connections joining successive sections of Well drill pipe. Such a coupling is illustrated in Figs. 2 and 3, in which well drill pipe sections 30 have upset ends 3| secured in sockets 40 and 4I of a coupling by means of threads 42. Intermediate the sockets 48 and 4I of the coupling is a body portion 43 of reduced diameter with respect to the diameter of well drill pipe sections 30. 'I'he inside and outside diameters of this body portion 43 bears a similar relationship to the inside and outside diameters of the well drill pipe sections 3l] as the respective diameters of the joint part IB, so that the mean diameter of the body portion 43 is less than the mean diameter of the pipes 30.
By decreasing the internal diameter of the body portion 43 a relatively greater amount than the external diameter is decreased, the effective cross-sectional area of the metal forming the body portion 43 of the coupling may be maintained substantially equal to or even greater than the cross-sectional area of the body portion of the pipe section 30. In Fig. 3 the relationship between the diameters and the cross sectional areas of the body portion 43 of the coupling and the body portion 32 of the well drill pipe are shown to advantage. It is clear from Fig. 3 that the shaded portion G which represents one-half of the area of a cross-section of the body portion 43 of reduced diameter, is substantially equal to the shaded portion H which represents one-half of the area of the cross-section of the body portion 32 of a well drill pipe 30. Accordingly, it is apparent that, although the resistance to bending of the body portion 43 of the coupling is substantially less than the resistance to bending of the body portion 3l] of the well drill pipe, the tensile strength, which is a function of the crosssectional area, need not be materially impaired.
The relationship g between the cross-sectional areas of the body portion 43 of the couping and the body portion 32 of the well drill pipe described in connection with Figs. 2 and. 3 may likewise be applied to the cross-sectional areas of the body portions I4 and 24 of the joint parts I0 and 2U, as compared with the cross-sectional area of the pipe.
It is preferable that the reduced diameter body portion 43 be of considerable length in order that bending stresses will not be concentrated over a short length. As mentioned in connection with the tool joint shown in Fig. 1, the longer the reduced diameter body portion is made, the less concentrated and less severe will be the bending stresses in such portion. The stress in the body portion of reduced diameter appears to vary with the length of such body portion; with relatively short lengths `the stress is greater than with relatively long lengths.` Satisfactory results are obtained when the length of such body portion is substantially equal to its internal diameter, but it is preferable, as shown in the drawing, that its length be considerably greater than its diameter.
In order to further avoid concentration of stress in the coupling, the shoulder portions 44 which lie intermediate the body portion 43 and end socket portions 4i) and 4I are preferably constructed with a smooth contour so that there is a gradual transition fromthe cross-sectional area of socket or box portions and 4I to the cross-sectional area of the body portion 43. Thus, there is an avoidance of sharp cracks and corners, and a minimum localization of ben-ding stress; the bending of the well drill stem absorbed by the coupling will primarily occur in the body portion of reduced diameter.
In Fig. 4 is illustrated a modified form of coupling. This coupling is to be used in a manner similar to the coupling shown in Figs. 2 and 3. Accordingly, the parts of the coupling which correspond to similar parts of the coupling shown in Figure 2 have been indicated by the same numerals of reference.
It is desirable in some applications to provide portions of substantial length longitudinally of the coupling to be engaged by wrenches in assembling and disassembling the coupling and oil drill pipe sections with which it is used. This is accomplished in the coupling illustrated in Fig. 4 by means of circumferential wrench lands 50 which are positioned adjacent the sockets 4U and 4I. These lands are relatively thin and are separated by annular grooves 5I. The outside diameter of the wrench lands is substantially equal to the outside diameter of the sockets 40 and 4I, so that wrenches may engage both the wrench lands and the sockets of the coupling. Portionsof the coupling are thus provided which are of considerable axial length for engagement with wrenches.
The reduced diameter body portion 43 has an eiective length which is substantially equal to the distance between the sockets 40 and 4I. Thus, increased flexibility is imparted to the coupling in combination with an extended wrench-engageable area without an increase in its length, which would be objectionable in the commercial manufacture of such couplings.
In the commercial manufacture of couplings and joints embodying the present invention, it is to be understood that various materials may be used which have the desired characteristics of elasticity, toughness and strength. Such materials may include various alloys of steel, such as alloys of steel with nickel and chromium. Furthermore, the metal may be heat treated to improve its quality.
It will thus be seen that I have provided an improved coupling or joining means for use in connection With well drill pipe with sufficient inherent flexibility with respect to the pipe sections included in the whole well drill pipe, so that the couplings and joint parts will absorb considerable of the bending induced in the drill pipe or tool during a drilling operation. In operation, the drill hole is seldom straight, and as the string of drill pipe is turned in the drill hole the bending stresses that are caused by each rotation of the pipe string are distributed not only in the body portions of the pipe but also in the tool or pipe joints and couplings between the pipe sections. The flexibility of the body of the tool joints and couplings described above also relieves the pin and box joints of a considerable portion oi the bending stresses that would otherwise be imposed on the threads by a conventional tool joint or coupling.
The substantial increase in the uniformity of the flexing of the drill pipe or tool materially prolongs the life of the threaded engagement between the sections and minimizes the galling and the injury of the section joining threads that results from the localization of strains at tool joints and couplings and greatly reduces the delay and expense that results from the galling of the threads and the separation of the string of drill pipe in deep well operations.
It is to be understood that the particular form and construction of the reduced diameter body portion of well drill pipe joints and couplings embodying the present invention may be considerably modied and altered from that shown in the accompanying drawing and described above, and
it is intended to include such modifications within the scope of the appended claims.
What I claim is:
1. Means for coupling adjacent ends of threaded drill pipe sections, comprising a sleeve having threaded ends for receiving the ends of the drill pipes, said sleeve havingy a relatively long body portion, the inside and outside diameters of Which are less than the corresponding diameters of the pipe sections to provide for a iexing of the sleeve at least equal to the amount of exing occurring in the pipe sections under operating conditions.
2. Means for coupling adjacent ends of threaded drill pipe sections, comprising a sleeve having threaded ends for receiving the ends of the drill pipes, said sleeve having a relatively long body portion, the inside and outside diameters of which are less than the corresponding diameters of the pipe sections to provide for a flexing of the sleeve at least equal to the amount of flexing occurring in the pipe sections under operating conditions, and said body portion having annular enlargements for receiving a pipe wrench or tongs.
3. Means for coupling adjacent ends of threaded drill pipe sections, comprising a pair of sleeves, each having a threaded end for receiving the end of a drill pipe, means for joining the sleeves together, and said sleeves having relatively long body portions, the inside and outside diameters of which are less than the corresponding diameters of the pipe sections to provide for flexing of the sleeves at least equal to the amount of iiexing occurring in the pipe sections under operating conditions.
li. Means for coupling adjacent ends of threaded drill pipe sections, comprising a pair of sleeves, each having a threaded end for receiving the end of a drill pipe, means for joining the sleeves together, said sleeves having relatively long body portions, the inside and outside diameters of which are less than the corresponding diameters of the pipe sections to provide for flexing of the sleeves at least equal to the amount of flexing occurring in the pipe sections under operating conditions, and annular enlargements on one of said sleeves for receiving a pipe wrench or tongs.
BERT L. PETERSON,