Well digging apparatus

D. E. STRA1T1FF

WELL DIGGING APPARATUS

2,653,794

Sheets-Sheet 1

Sept. 29, 1953

Filed April 25, 1949

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Sept. 29, 1953 d. e. straitiff 2,653,794

WELL DIGGING APPARATUS

Filed April 25, 1949 3 Sheets-Sheet 2

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arToeA/Eds

Sept. 29, 1953

2,653,794

D. E. STRAIT1FF

WELL DIGGING APPARATUS

Filed April 25, 1949

Sheets-Sheet 3

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fiT7ORNeYS

Patented Sept. 29, 1953

2,653,794

UNITED STATES PATENT OFFICE

2,653,794

WELL DIGGING APPARATUS Dorsey E. Straitiff, Beverly Hills, Calif. Application April 25,1949, Serial No. 89,507

Claims. (Cl. 255—1)

This invention relates to apparatus for the digging of wells and is particularly directed to a device having a relatively large number of power driven digging elements.

In a conventional rotary system for the boring of oil wells a bit is carried on the lower end of a drill pipe string and is rotated by power applied at the upper end of the drill pipe string near the surface of the ground. As the well hole is deep- _i , ened, additional sections are added to the drill pipe string. Conventional drilling bits are provided with hard cutting edges or with rotary cutters each formed of hard material or having cutting teeth surfaced with hard metal such as, for _ example, tungsten carbide. The bit and cutters ¹⁰are subjected to very severe service and only a relatively small number of teeth can be provided on the cutters because of limitations of space. Accordingly, there are relatively few cutting elements which can be brought into play against the ²⁰formation, and the result is that the bit must be withdrawn at frequent intervals and replaced by a new one. This requires that the drill pipe string be withdrawn from the hole and unjointed section by section and then reinserted in the i³same manner. As the well hole is deepened it is not uncommon to spend as much or more time withdrawing and reinserting the drill string as is spent during the drilling operation with the bit on bottom. 30

In accordance with my invention I provide a relatively large number of formation-contacting digging elements each formed of hard material or having a cutting edge surfaced with tungsten carbide or other hard metal. Since I employ a 35 very large number of these digging elements, a much greater depth can be cut before it is necessary to withdraw the device for replacement. Indeed,' under good drilling conditions it is contemplated that the device may operate satisfac- 40 torily for the full depth of the completed well.

Accordingly, it is the principal object of my invention to provide a large number of hard metal or hard surfaced digging elements engageable with the well formation. . 43

Another object is to provide a plurality of vertically extending chains having links provided with hard metal teeth for engaging the formation at the bottom of the well hole.

A more detailed object is to provide such a de- 50 vice having a central chain rotating in one direction between side chains rotating in the opposite direction in order that the well hole may not vary from the vertical for any great extent.

Another object is to provide a well digging de- 55 vice having vertically extending chains for contacting the well formation and having a novel form of power applying means for rotating the chains from a conventional rotary drill string.

Another object is to provide a well digging device of this type in which digging chains pass over coaxial sprockets for engaging the formation, certain of the chains being driven by driving sprockets positioned above the coaxial sprockets and certain other chains being driven by certain of the coaxial sprockets.

Another object is to provide a well digging device of this type for digging a noncircular hole, the device being provided with corner shoe elements for absorbing the reaction torque against the walls of the hole.

Another object is to provide a well digging device having parallel digging chains of varying length so that drive mechanism therefor does not overhang the outline of the hole dug by the chains.

Another object is to provide a well digging device having a plurality of vertically extending chains for contacting the well formation, each of the chains being trained over vertically spaced sprockets, the chains on the outer faces of the device being effective to dig either in an upward or downward direction.

Another object is to provide a well digging device having vertically extending formation-contacting chains, which device is adapted for vertical, horizontal, inclined or curved drilling.

Another object is to provide a device of this type incorporating shock absorbing means interposed between the rotary drill string and the hole deepening device at the lower end thereof.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

Figures 1, 2 and 3 are elevation views partly in section showing a preferred embodiment of my invention. In practice the structure shown in Figure 2 is interposed between the structure shown in Figure 1 and Figure 3, the lower end of Figure 3 illustrating the lower end of the device. The formation-contacting chains have been largely omitted in Figures 2 and 3 for clarity of illustration.

Figure 4 is a transverse sectional view taken substantially on the lines 4—4 as shown in Figure 1.

Figure 5 is a transverse sectional view taken substantially on the lines 5—5 as shown in Figure 3.

Figure 6 is an enlarged side elevation taken in

2,653,784 the direction 6—6 as shown in Figure 3 and illustrating the action of the digging teeth on the chains.

Figure 7 is a sectional elevation showing a modified form of mounting for the idler sprockets.

Figure 8 is a sectional elevation showing a modified form of gearing assembly.

Figure 9 is a transverse sectional view taken substantially on the lines 9—9 as shown in Figure 3.

Referring to the drawings, a nonrotary frame assembly generally designated 10 is carried at the lower end of a drill string 11 and supports a cutting head 12 at its lower end. A plurality of coaxial sprockets 13, 14 and 15 are mounted on the cutting head. A driving sprocket 16 is rotatably mounted on the upper portion of the frame assembly 10 and is aligned with the driven sprocket 13. A second driving sprocket IT is rotatably mounted on the frame assembly 10 and is aligned with the sprocket 14α of the double sprocket member 14. The other sprocket 14b of the double sprocket member 14 is aligned with the idler sprocket 19 rotatably carried by the upper portion of the frame assembly 19. The sprocket 15 is aligned with the idler sprocket 19, also rotatably mounted on the frame assembly 10. A formation-contacting chain 20 is trained over aligned sprockets 15 and 19 and similar chains 21, 22 and 23 connect aligned sprockets 14b and 18, 14α and IT, and 13 and 16. The individual links 24 of each of the chains are each provided with hard digging teeth 25 which may be surfaced with tungsten carbide or other hard surfacing material. The digging chains operate with verv little side clearance between them and engage substantiallv the full area of the bottom of the well hole. Since the individual links on each chain are staggered, and since each link carries a cutting tooth, the teeth cooperate to engage the entire area of the formation at the bottom of the hole. Power means is provided for rotating the outer chains 20 and 23 in one direction and for rotating the inner chains 22 and 21 in the other direction.

The frame assembly 10 and its associated parts are connected through telescoping members 26 and 2T to the lower end of a conventional rotary drill string II. A coil spring 28 internosed between the telescoping parts 26 and 2T forms a shock absorbing device described more fully hereinafter.

The drill string 11 is supported from the surface in a conventional manner and is rotated bv means of the usual rotarv machine (not shown). Hvdraulic fluid is pumped down the interior of the drill string, and this fluid emerges adjacent the lower end of the device near the sprockets 13, 14 and 15. The hydraulic fluid carries the cuttings from the hit un through the annular snac.e between the drill strln” and the well hole in the usual manner. Rotation of the drill string acts through a bevel rear assembly generally designated. 29 and a spur gear train generally designated 30 to rotate the driving sprockets 16 and IT in opposite directions. The driven sprockets IS and (6 are fixed tn a common shaft 31 so that they rotate as a unit. Conseouentlv when the sprockets 16 and IT are rotated in opposite directions the outer chains 20 and 23 rotate in one direction while the inner chains 21 and 22 rotate in the other direction. As the chains pass around the lower portions of the driven sprockets the digging teeth 25 are exposed and contact the formation at the bottom of the well hole.

Considering the various elements of this embodiment of my invention in more detail, the shaft 31 is rotatably supported in axially spaced bearings 32 carried within parallel webs 33 which are formed integrally with the drilling head 12. The double sprocket member 14 is rotatably mounted on the shaft 31 by means of bearings 8, while the sprockets 13 and 15 are each fixed to the shaft by means of a suitable key 9. Retaming nuts T are threaded to the ends of the shaft 31 to hold the parts in assembled relationship. The drilling head 12 is mounted for relative longitudinal movement with respect to the lower end of the frame assembly 10, and as shown in the drawings the connecting parts include a crosshead 34 fixed on the lower end of the member 35 and having parallel openings for the reception of threaded elements 36. Lock nuts 3T cooperate with each of the threaded elements 36 so that the threaded elements are adjustably positioned with respect to the cross-head 34. The threaded elements 36 are fixed at their lower ends to the drilling head 12. The longitudinal adjustment provided by the threaded elements 36 and lock nuts 3T enables the chains 20, 21, 22 and 23 to be tensioned before the drilling or digging operation commences.

The drilling head 12 carries a pair of upwardly projecting tubular parts 38 which are slidably received within parallel bores 39 provided in the member 35. Sealing rings 40 may encircle the tubes 30 to prevent leakage. Hydraulic fluid passing downwardly through the interior of the frame assembly 10 enters the tubes 38 and passes into the chamber 41 within the drilling head 12. As shown in Figure 6 the hydraulic fluid is then directed against the interior surfaces of the digging chains by means of suitably oriented nozzles 42.

Stationary stub shafts 43 and 44 are carried on the frame assembly 10 at a location considerably above the location of the driven sprockets 13, 14 and 15. It will be noted that a break in the frame assembly 10 is indicated in the region of the numeral 45. The digging chains are relatively long and the stub shafts 43 and 44 may therefore be mounted a considerable distance away from the driven sprockets 13, 14 and 15. Suitable bearing assemblies 46 and 4T are provided for mounting each of the idler sprockets 18 and 19 on its respective stub shaft.

Near the upper end of the frame assembly 10 are positioned the power shafts 48 and 49 for driving the sprockets 16 and IT. Each of these sprockets is secured on its shaft by any convenient means such as, for example, a press fit. The shafts are supported in axially spaced bearings 50 carried in shells 51 secured to the frame assembly 10. A spur gear 52 fixed to the shaft 48 rotates the driving sprocket 16. Similarly, a spur gear 53 fixed to the shaft 49 rotates the driving sprocket IT. The gears 52 and 53 are in mesh so that the shafts 48 and 49 rotate in opposite directions. The gear 52 is driven from a spur pinion 54 secured on the side face of the bevel gear 55. The bevel gear 55 and pinion 54 are rotatably mounted by means of bearings 5T on a nonrotary stub shaft 56 which is supported at both ends on the frame assembly 10. The inner end of the stub shaft 56 is carried on a plate 58 fixed to the frame assembly 10. The bevel gear 55 is driven from the bevel pinion 59 carried at the lower end of the hollow drive shaft

2,653,784

60. The drive shaft 60 is rotatably mounted in axially spaced bearings 61 and 62. A sleeve 63 is threadedly connected at its upper end to the housing 64 for the bearing 62. The hollow drive shaft 60 is threadedly connected at 66 to the connector element 67. A gland 68 may encircle a portion of the connector element 67 for applying pressure to the packing 69.

The connector element 67 may be directly attached to the lower end of the drill string 11 or, as shown in the drawings, it may be connected to a shock absorbing device which includes the telescoping members 26 and 27 and the compression spring 28. As shown in Figure 4, drive splines 70 extend axially of the member 27 and 15 fit within longitudinal recesses provided in the member 26. These splines carry the torque which is transmitted from the drill string 11 to the lower telescoping member 27. Radial pins 72 are threadedly mounted on the member 26 20 and extend outwardly into longitudinally extending slots 73 provided in the member 27. These pins cooperate with the slots to limit the extent of axial movement between the members 26 and 27. The member 27 is attached to the 25 lower end of the drill string ί I by way of connection pieces 74 and 75. An upwardly extending tube 76 is received telescopically within the member 75, and this tube is connected at 77 to the member 26. Packing 78 may be provided 30 between the members 74 and 76 and a gland 79 may be threaded within the member 74 for compressing the packing 78. The purpose of the packing is to prevent leakage of hydraulic fluid from the interior of the tube 76. The hydraulic 35 fluid passes downwardly through the tube 76, member 26, connector 67 and hollow drive shaft 60. The tube 80 is fixed within the lower end of the hollow shaft 60 and extends downwardly into a stuffing box 81 carried on the frame as- 40 sembly fO. The fluid then passes around the shells 51 and downward within the frame assembly iO and into the bore 39 in the member 35 at the lower end of the frame assembly 10. Suitable seals may be provided for each of the shaft bearings if desired in order to retain lubricant and to exclude the hydraulic fluid.

From this description it will be understood that the drive means including the drive member 60, the gearing 29 and gear train 30, as well _Mas the bearings for the drive sprockets 16 and 17, operate in a lubricant bath and are not exposed to the action of the hydraulic fluid which is pumped down the interior of the drill string 11. If desired a small lubricant-carrying pipe can be provided which communicates with the enclosed gear chamber and which extends downwardly through the frame assembly 10 and communicates at its lower end with the bearing assemblies 8 and 32 for the coaxial sprockets. βθ In the modified form of my invention shown in Figure 7 the idler sprockets 18a and 19α are mounted for independent vertical adjustment with respect to the frame assembly 10α. The pintles 43α and 44α for the sprockets 18α and 19α 65 respectively are fixed to brackets 90 and 91 which are adapted to be slidably mounted in ways or grooves 92 provided on the frame assembly i0α. Clamping bolts 93 serve to hold the brackets 90 and 9! in adjusted position on the frame assem- 70 bly 10α. Since the digging chains 20, 21, 22 and 23 are of different lengths, it is desirable to have independent means for adjusting the tension therein, and this is provided by means of the apparatus shown in Figure 7. 75

In the modified form of my invention shown in Figures 8 and 9, fiber bearings 100 replace the roller type bearings 61 and 62 shown in Figure 2. These bearings 100 rotatably support the hol5 low driving member 103 which is threadedly connected at its lower end to the bevel pinion 104. The bevel gear member 105 has the spur pinion 106 formed integrally therewith, and this member is rotatably mounted on fiber bearings 107. The wash pipe 108 is stationary and is secured to the frame assembly at 109 adjacent its lower end. This wash pipe 108 projects upwardly in telescopic relation through the bevel pinion 104 into the hollow drive member 103. Suitable packing 110 is provided in a recess in the driving member 103, and a gland 111 is provided for expanding the packing against the wash pipe 108.

The spur gear I (2 which is driven by the spur pinion 105 is fixed on the drive shaft 113 and serves to turn the driving sprocket 16α which is keyed to the shaft ί 13. A fiber bearing 114 rotatably supports the shaft 113 within the stationary tubular housing 115.

The driving gear 116 which is driven by the gear 112 is fixed on the drive shaft 117 and serves to drive the driving sprocket 17α which is keyed to the shaft. A fiber bearing 118 encircles the shaft near the gear 116, and this bearing is supported in a tubular housing 119. An outboard bearing assembly 120 is provided for the end of the shaft 117 opposite the gear 116. This bearing assembly 120 includes a fiber bearing element 121 carried in a housing 122, and this housing is supported on diverging fins 123 carried on the frame assembly 10α at their lovzer ends.

Suitable sealing elements 124 are provided on the driving sprockets IBs and 17α for confining lubricant within the shaft hearings and for lubricating the gears.

The ground-engaging chains for the driving sprockets IGa and 17α may be the same as that shown generally in Figures 2 and 3 or may comprise a five element assembly instead of a double triple element assembly. In any event, each of the links of the chain carries a formation-engaging tooth as clearly shown in Figure 6.

Since the digging device is powered by a rotary drill string having an axis of rotation extending longitudinally of the hole, the frame assembly of the device tends to turn in the opposite direction from the direction of rotation of the drill string. This torque reaction may be carried directly on the outer chains 19 and 23 as described above or corner torque-receiving shoes may be provided on the frame assembly to absorb this torque reaction substantially independently of the digging chains. These torque-receiving shoes may be mounted at vertically spaced intervals on the frame assembly 10α between the drilling head 12 and the lower idler sprocket, and as shown in Figure 9 each of these shoes J3S may be secured on the frame assembly 18a and be provided with a face 131 which engages a corner of the noncircular hole. Each of the shoes 139· may be provided with a relatively thin outwardly extending section 132 which is positioned between a pair of the digging chains and a transversely extending portion 132 which extends to the face i3. These torque-absorbing shoes i30 are mounted only on diagonally opposite portions of the frame assembly 10α and on the slack sides of the digging chains 19 and 23. The working diameter of these digging chains when passing over their respective sprock9,663,704

Ί ete is substantially the same as the over-all lateral dimension of the device including the torqueabsorbing shoes 130. Since one flight of each of the chains is slack during operation, these slack flights extend under the portions 132 of the shoes ISO and emerge therefrom at each end to pass around their respective sprockets. It will be noted that the outer links in each of the chains 20 and 23 have laterally extending teeth 25α which extend beyond the side face of the links to provide clearance for the frame assembly 10α.

In operation a shallow preliminary hole is drilled from the surface by conventional means. The frame assembly 10α and associated parts is then attached to the lower end of the drill string 11 below the rotary machine, and the drill string is lowered until the digging chains contact the bottom of the preliminary hole. Torque-resisting means are then applied to the frame assembly ίθα. This may be accomplished by clamping suitable arms to the sleeve 63 or other part of the frame assembly 10α above the upper driving sprocket 16. Such torque arms (not shown) extend radially and contact fixed elements of the derrick or substructure commonly employed in rotary well drilling operations. The drill string ί ( is then rotated by means of the rotary machine (not shown) and it is lowered into the hole sc that pressure develops on the digging teeth 25. The digging teeth enter the formation and deepen the hole. The cuttings are carried upwardly out of the hole by means of the stream of hydraulic fluid supplied through the interior of the drill string. After the hole has been deepened for a number of feet by the digging chains, the torque resisting clamps are discarded. The hole which is produced by the digging chains is noncircular in outline and therefore the walls of the hole prevent rotation of the frame assembly ί 9α and digging chains about the axis of the drill string. Continued rotation of the drill string 11 continues the digging operation of the chains 20, 2i, 22 and 23.

If the chains were all to rotate in the same direction, the action of the device would be to veer away from the vertical, but since the outer chains 20 and 23 rotate in one direction while the inner chains 21 and 22 rotate in the other direction, tliis tendency is eliminated. The torque imposed on the frame assembly ί 0 by the drill string ί ί is resisted by the side walls of the hole as it is deepened, and accordingly there may be some tendency of the device to wind or spiral gradually as the hole is deepened. This has no disadvantageous effect, however.

Conventional rotary drill bits are ordinarily designed only for cutting on the bottom of the hole. Occasionally formations are encountered which swell upon contact with the drilling fluid with the result that the hole becomes smaller as the bit deepens the hole. When it is desired to withdraw the bit for replacement, difficulty is encountered under such conditions because the bit is ineffective to drill in an upward direction. My improved digging device overcomes this difficulty because the digging chains will dig upwardly as well as downwardly. Thus, the digging teeth 25 are exposed as the links 24 of the digging chains travel around the drive sprockets and idler sprockets. Accordingly, the device may be used to dig itself out in the event that “heaving shale” or other swelling formation should be encountered. Furthermore, the fact that these digging chains are also effective to dig in an upward direction prevents possible sticking of the drilling unit in the hole by deposit of Alter cake or mud on the walls of the hole.

Since the digging chains may be made as long as is considered practicable, and since a very large number of digging teeth may therefore be employed, the hard surfaced teeth do not become dulled for a much greater length of time than is the case where only a few teeth are provided on the end of a conventional rock bit. Accordingly, it is unnecessary to withdraw the device from the well hole at frequent intervals for the purpose of replacing worn cutters.

While I have described my invention in connection with the digging of wells, it will be understood that the apparatus may also be used for digging horizontal, inclined cr curved holes or for digging other holes in the earth such as, for example, footings for concrete foundations, bridge piers, etc. Furthermore, the essential features of my invention may be employed in devices for forming or cutting noncircular holes in various materials.