Patent Publication Number: US-4580643-A

Title: Adjustable bearing section core barrel

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of earth-boring tools, and more particularly to a core barrel and a coring tool. 
     2. Description of the Prior Art 
     A coring tool is used to cut cylindrical cores from a rock formation, which cores are then retrieved for later laboratory analysis and examination. Thus, a coring tool generally comprises a coring bit which cuts a cylindrical core from the rock formation. As the core is cut, it moves within an inner gage of the coring bit, and is disposed within the outer tube or drill collars which are coupled to the coring bit. The drill collars are in turn coupled to drill pipe which constitutes the outer portion of the drill string and extends to the well surface. Within the outer tube of the coring tool is one or more sections of an inner tube assembly, including a core catcher disposed at the lower end of an inner tube shoe assembly. The core catcher is a device which engages the core through an interference fit and, when the coring tool has an upward tension placed thereon, jams between the core and the inner tube shoe assembly in order to seize the core, break it from the rock formation, and to retain it within the coring tool for retrieval at the well surface. 
     However, the inner tube assembly as manufactured and assembled in combination with various core bit designs does not have an exact length, but is characterized by a length which varies within a certain range. This range determines then the amount of spacing between the lower end of the inner tube assembly and the coring bit. This displacement is important in establishing the hydraulic communication from the interior of the drill string to the inner gage of the coring bit, and in providing a smooth transition between the inner gage of the coring bit and the lower end of the inner tube in order to minimize the disturbance of the core as the inner tube slides along the length of the core. 
     In order to accommodate these variations, the prior art practice in the field is to dispose a plurality of shims or washers within the coring tool in order to provide fine adjustments between the inner tube and coring bit. Generally, this requires disassembly of the cartridge cap from the safety pin in order to insert the shims or washers. This disassembly and assembly necessarily entails a certain amount of rig downtime during which all drilling operations are suspended. 
     Therefore, what is needed is some means whereby the longitudinal adjustment of an inner tube assembly within a coring tool can be quickly and easily made so that the loss of expensive rig time in the field can be avoided. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is an apparatus included within a coring tool whereby longitudinal displacement of the inner tube within the outer tube of the coring tool is selectively adjustable and lockable without requiring disassembly of the coring tool. The apparatus comprises a cartridge cap assembly which is disposed in the outer tube. The cartridge cap assembly is longitudinally adjustable within the outer tube and the inner tube is coupled to the cartridge cap assembly. Thus, by longitudinal adjustment of the cartridge cap assembly, the longitudinal displacement of the inner tube within the coring tool can be arbitrarily selected. The apparatus also includes a locking mechanism for locking the cartridge cap assembly within the outer tube in a selected longitudinal position. In the preferred embodiment, the cartridge cap assembly includes a radially expandable component and the locking mechanism co-acts with the radially expandable component to selectively fix the longitudinal position of the cartridge cap assembly within and with respect to the outer tube. 
     More specifically, the invention is an adjustable core barrel section in a coring tool, which includes an inner and outer tube. The adjustable section comprises an adjustable cartridge cap, a plurality of fingers and a frustoconical jam nut. The adjustable cartridge cap is telescopically disposed within the outer tube and is provided with external threading. The outer tube is similarly provided with corresponding or mating internal threading. By this means, the cartridge cap and the outer tube are threadably coupled together and are longitudinally displaceable with respect to each other by rotation of the cartridge cap within the outer tube. The plurality of fingers are defined in an upper portion of the cartridge cap. The plurality of the fingers are defined by corresponding plurality of longitudinally extending slots defined through the cartridge cap. The plurality of fingers are characterized by their radial resiliency. The cartridge cap in turn is coupled to the inner tube. Finally, the frustoconical jam nut is telescopically disposed within the plurality of the fingers of the cartridge cap. The jam nut is provided with exterior threading on its frustoconical surface. The plurality of fingers are correspondingly provided with mating internal threading. The jam nut and plurality of fingers are threadably coupled with each other thereby providing for longitudinal displacement of the jam nut within the fingers. By reason of this combination of elements, a longitudinal displacement of the jam nut with respect to the plurality of fingers causes the fingers to radially expand thereby locking the cartridge cap with respect to the outer tube, or allows the fingers to radially contract thereby freeing the cartridge cap with respect to the outer tube. 
     These and other details and embodiments of the invention can better be visualized and understood by now turning to consider the following drawings wherein like elements are referenced by like numerals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a core barrel assembly incorporating the invention. 
     FIG. 2 is a perspective illustration of a jam nut lock wrench used to unlock and lock the adjustable core barrel section. 
     FIG. 3 is a side elevational view of a cartridge cap rotating wrench used to adjust the core barrel section. 
     FIG. 4 is a cross-sectional view of the adjustable cartridge cap shown in isolation of the remaining portions of the core barrel assembly. 
     FIG. 5 is a longitudinal cross-sectional view of the jam nut used to lock and unlock the adjustable cartridge cap of FIG. 4 as shown in the assembled view of FIG. 1. 
     The invention and its various embodiments are better understood by now turning to the following detailed description. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention permits a longitudinal adjustment of the bearing assembly within the drill string from the top end section of the safety joint assembly, and does not require disassembly of the cartridge cap. This allows the longitudinal displacement between the core catcher and the inside diameter of the coring bit to be easily and quickly adjusted to a preselected distance, as well as generally providing for adjustment of the inner barrel within the coring tool. 
     A cartridge cap rotating wrench is used to engage the cartridge cap. The cartridge cap is then rotated in either direction to longitudinally advance or retract the cartridge cap within the safety joint assembly to which it is threaded. When the desired longitudinal position of the cartridge cap has been attained, a jam nut wrench is axially inserted through the cartridge cap wrench. The jam nut wrench has a socket projection which mates with a socket indentation in a jam nut which is threadedly coupled in the end of the cartridge cap. This threaded end of the cartridge cap in turn is comprised of a plurality of fingers, thereby allowing for radial expansion. The cartridge cap can then be locked within the safety joint assembly at the adjusted longitudinal position by advancing the jam nut and spreading the fingers of the cartridge cap. The invention is better understood by now turning to consider in detail the preferred embodiment as illustrated in FIGS. 1-5. 
     Turn first to FIG. 1, which illustrates a longitudinal cross-sectional view of a core barrel assembly, generally denoted by reference numeral 10. Core barrel assembly 10 in turn is comprised of a safety joint assembly 12, including a conventional pin and box connection 14 to which drill pipe or collar can be threadably connected. Safety joint assembly 12 in turn is threadably coupled to an outer tube 16. Outer tube 16 is next threadably coupled to outer tube sub 18. A plurality of wear ribs 20 may also be disposed on the outside of outer tube 16, and serve to absorb a substantial part of the friction of wear between the bore hole and the coring tool, which may arise due to an undergage diameter, diametral eccentricity or other irregularities in the bore hole. Outer tube sub 18 in turn is threadably coupled to lower outer tube sub 22, also provided with wear ribs 20. Finally, outer tube sub 22 is threadably coupled to shank 24 of a coring bit, generally denoted by reference numeral 26. Coring bit 26 is comprised of outer gage 28, crown 30, and an inner gage 32. In combination, each of these elements comprise the outer casing of the coring assembly. 
     Consider now the internal components within coring assembly 10, as depicted in FIG. 1. Beginning again at the top of the coring assembly, an adjustable cartridge cap 34, as will be further described in connection with FIG. 4, is threadably disposed within safety joint assembly 12. Adjustable cartridge cap 34 is provided with threading 36 which engages the threading defined in safety joint assembly 12. Safety joint assembly 12 in turn is threadably coupled in turn by threads 40 with internal matching threading defined in lower section 38 of the safety joint assembly. Lower section 38 is coupled to the upper section of safety joint assembly 12 by means of a friction ring 40 circumferentially disposed about the upper section of assembly 12 and locked thereto by means of an annular locking ring 42 which is mutually disposed within an annular groove defined in friction ring 40 and in the upper section of assembly 12. An internal pressure plug 44 is disposed in a radial bore 46 defined through lower section 38, and provides a means for selectively relieving any hydraulic overpressures which may be created within the interior of the drill string, and in particular outer tube 16. 
     Jam nut 48 is threaded into the upper end of adjustable cap 34. As will be better described and illustrated in connection with FIG. 4, the upper end of adjustable cartridge cap 34 is comprised of a plurality of fingers 50, which are radially expandable by the longitudinal engagement of jam nut 48 within the upper end of cartridge cap 34. 
     The lower end of cartridge cap 34 is rotatably coupled to a swivel assembly generally denoted by reference numeral 52. Swivel assembly 52 is comprised of a annular ball bearing 54 disposed within an annular raceway 56 of the lower end of cartridge cap 34, and in an adjoining annular recess 58 defined in bearing retainer 60. Bearing retainer 60 in turn is threadably coupled to an inner tube plug 62. Inner tube plug 62 and bearing retainer 60 thus form a single assembly which is rotatably free with respect to outer tube 16 by virtue of ball bearing 54. Therefore, as outer tube 16 rotates, ball bearing 54 allows inner tube plug 62 to remain stationary. 
     Hydraulic fluid is pumped down the interior of the drill string and enters core barrel assembly 10, as indicated by the arrows, and flows through the pin and box connection 14, through jam nut 48, down the interior of cartridge cap 34 and through bearing retainer 60 into inner tube plug 62. A steel ball 62 is selectively used to plug a longitudinal bore 66, thereby forcing the hydraulic fluid through a plurality of bypass ports 68 defined in inner tube plug 62. The hydraulic fluid is thus forced outwardly to an annular space 70 between inner tube plug 62 and outer tube 16. Although in the present invention, ball 64 is generally disposed and placed to seal bore 66, and thereby force hydraulic fluid through bypass port 68, it is entirely within the scope of the invention that ball 64 may be omitted to allow hydraulic fluid to freely flow into the interior of inner tube 72, or to such other apparatus and mechanisms lying below swivel assembly 52 which may be operative upon the application or withdrawal of hydraulic fluid and pressure caused by the blockage of bore 66 by ball 64. As is conventional in the art, ball 64 in such a case would be dropped into the drill pipe at the well surface, and ultimately would come to rest to lodge against the opening of bore 66. 
     The lower portion of inner tube plug 62 is threadably coupled to inner tube 72, into which the core is disposed. Inner tube 72 continues longitudinally downward within the core barrel assembly 10 through outer tube subs 18 and 22, and is ultimately threadably coupled to an inner tube shoe assembly 74. Inner tube shoe assembly 74 in turn is arranged and configured at its lower end to accommodate core catcher 76, and to be threadably coupled to an inner tube shoe pilot 78. Inner tube shoe pilot 78 is similarly arranged and configured to coact with core catchers 76, and provides an inwardly tapering frustoconical surface on which core catcher 76 rides. As core catcher 76 is longitudinally displaced downward within the inner tube, this surface serves to radially compress core catcher 76 against the core which is disposed through it. 
     Thus, inner tube shoe pilot 78 represents the lowermost portion of the inner tube string, and defines a gap 80 between inner tube shoe pilot 78 and the adjacent inner surface 82 of core bit 26. 
     Before considering the overall operation or adjustment of the inner barrel within core assembly 10, turn first to the longitudinal cross section of cartridge cap 34 shown in isolation from the other elements of the assembly 10. Cartridge cap 34 is clearly illustrated in FIG. 4 as including a plurality of fingers 50 defined by longitudinal slots 84 defined through cartridge cap 34. Thus, fingers 50 comprise a plurality of longitudinally extending fingers capable of resilient radial expansion is described below in greater detail. Alternate fingers 50 are provided with an extended, integral lug 86 for engagement with a cartridge cap wrench, again described in greater detail in connection with FIG. 3. The upper inside portion of fingers 50 is similarly provided with threading 88 with which jam nut 48 is coupled. In their unexpanded configuration, fingers 50 thus provide cylindrical internal threading. 
     Reviewing for a moment the remaining features of cartridge cap 34, an O-ring groove 90 is defined below fingers 50 in order to provide a hydraulic seal. The O-ring is shown in place in the assembled view of FIG. 1. Threading 36 is defined on a thickened shoulder portion 92 in the middle section of cartridge cap 34, which threading 36 as previously described is coupled to corresponding threading 38 defined in safety joint 12. Threading 36 in cooperation with threading 38 thus provides a means whereby the longitudinal position of cartridge cap 34 within the coring assembly 10 may be finally adjusted by rotation of cartridge cap 34 within coring assembly 10. 
     Below threading 36 a second O-ring groove 94 is defined, again shown in the assembled view of FIG. 1 with an O-ring in place. Cartridge cap 34 continues downwardly in an expanded bell housing to define a shoulder 58 into which ball bearing 54 will be disposed. Ball bearing 54, as shown in FIG. 1, is then retained within shoulder 58 by means of inner tube plug 62, and cartridge plug 57 on one hand, and bearing retainer 60 on the other, all of which are disposed, at least in part, within the lower portion of cartridge cap 34. 
     Before considering the tools used to adjust cartridge cap 34, turn now to FIG. 5 wherein a longitudinal section of jam nut 48 is illustrated. Jam nut 48 includes a hexagonal socket 96 defined at its upper end, and includes exterior threading 98 along its outer surface which are engageable with threading 88 defined in the interior of fingers 50 of cartridge cap 34. The outside surface defined by threads 98 of jam nut 48 define a frustoconical shape. In the illustrated embodiment, the angular taper of the exterior surfaces, or of the envelope of threading 98 of jam nut 48, define an angle 100 of 0.75 inches of taper per foot. Thus, jam nut 48 is characterized by a downwardly tapering frustoconical exterior shape with a hex head socket drive 96 formed in its upper portion. The degree of taper can of course be selected at any other value determined by design parameters. 
     Turn now to FIG. 3, which illustrates a cartridge cap rotating wrench generally denoted by reference numeral 102. Wrench 102 includes a hollow cylindrical body 104 with a radial driving handle 106 for hand grasping at one end, and a plurality of annularly disposed teeth 108 at the opposing end. Teeth 108 are arranged and configured to easily slide between lugs 86 of fingers 50, and when thus engaged thereby provide a convenient means for manually applying a torque to cartridge cap 34 through drive handles 106. 
     FIG. 2 illustrates a jam nut lock wrench, generally denoted by reference numeral 110. Jam nut lock wrench 110 is similarly comprised of a cylindrical body 112 having drive handles 114 disposed at one end, and provided with a hex head 116 at the opposing end. Hex head 116 is arranged and configured to appropriately mate and correspond with hex head socket indentation 96 in the upper end of jam nut 48. 
     The operation or adjustment of the inner barrel within coring tool 10 can now be explained. As coring tool 10 is assembled on the well platform, the interior components, including inner tube 72, are disposed within the outer portions of the drill string, and are threaded therein by means of threading 36 and 38 provided in cartridge cap 34 and safety joint 12, respectively. Cartridge cap 34 is threaded into safety joint 12 by means of wrench 102. When the approximate correct displacement 80 has been obtained between the lowermost end of the inner tube, in the illustrated embodiment a pilot shoe 78, jam nut 48 is then loosely threadably coupled into threading 88 of fingers 50, if not previously in place. As long as jam nut 48 is loosely threaded within fingers 50, jam nut 48 will not expand fingers 50, and will generally rotate with cartridge cap 34. Wrench 110 is then disposed through the hollow cylindrical bore 118 of wrench 102, and engaged with jam nut 48. Jam nut 48 is then tightened, thereby radially expanding fingers 50. Gap 80 is monitored, and wrench 102 appropriately adjusted as jam nut 48 is tightened by means of wrench 110. When the appropriate displacement 80 has been verified, jam nut 48 is then finally tightened, thereby securely locking cartridge cap 34 in place. Wrenches 102 and 110 are then removed, and core barrel assembly 10 connected by pin and box connection 14 to the drill string, and thereafter lowered into the bore hole. 
     Thus, it may be appreciated that according to the invention a mechanism and design is provided which allows very accurate, easily controllable, fine adjustments of the inner tube longitudinal displacement. When the coring bit is changed, or any other adjustment or change made to the inner tube, displacement 80 may be quickly and accurately readjusted by means of appropriate manipulation through the use of wrenches 102 and 110 without requiring any disassembly whatsoever of core barrel assembly 10 or cartridge cap assembly 34. 
     Many modifications and alterations may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. The illustrated embodiment has been set forth only for the purposes of example, and should not be taken as limiting the invention as defined by the following claims.