Abstract:
A coiled tubing hanger assembly for supporting coiled tubing in a well including, as a first element, a mechanically-assisted slip assembly characterized by multiple slip segments inserted in a tapered slip bowl located in the midsection of a coiled tubing head. The conical slips are constrained to move in concert in the tapered throat of the tubing head midsection by means of a slip retainer ring and rest on a rack cylinder slidably positioned in the bore of the midsection beneath the slips. The rack cylinder is typically fitted with lands and grooves that engage a pinion gear attached to a slip-operating mechanism to facilitate manually raising and lowering the rack cylinder and the slips together, causing the slip teeth to selectively engage and disengage the segment of coiled tubing extending through the slips and the bore of the rack cylinder, into the well. A pack-off assembly is located in the bore of a lower body secured to the midsection of the tubing head for sealing the coiled tubing against well pressure and pack-off screws are radially seated in the lower body to apply pressure to the pack-off assembly for achieving this purpose. A top bonnet is bolted to the top of the midsection and seats a slip cone shaped to engage the top inside surfaces of the slips to maintain the slips in the proper configuration in the midsection.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to devices and apparatus for suspending tubing, and coiled tubing in particular, in an oil or gas well and more particularly, to a manually-operated coiled tubing hanger assembly for suspending coiled or conventional tubing in a well without the necessity of “killing” the well. The coiled tubing hanger assembly of this invention is characterized by multiple, mechanically-assisted, tapered and collectively conically-shaped slip segments constrained to operate in concert by a retainer ring and positioned in the correspondingly tapered slip bowl of a specially designed tubing head, which includes a top bonnet, a midsection and a lower body, typically bolted together. In a preferred embodiment the slips rest on a rack cylinder having a central longitudinal bore and typically fitted with lands and grooves, which lands and grooves engage a pinion gear attached to one end of a slip-operating mechanism to facilitate manual vertical movement of the rack cylinder, and thus the slips, in the midsection. This action effects selective release and engagement of the slips with a segment of tubing such as coiled tubing, extending through the tubing head, to control insertion and retrieval of the tubing into and from an underlying well. A pack-off assembly is located in the lower body of the tubing head for sealing the coiled tubing hanger assembly against well pressure and the packing seal in the pack-off assembly is facilitated by tapered or bevelled-end pack-off screws extending radially through the lower body to engage the bevelled pack-off plate above the seals in the pack-off assembly. The conical base of a slip cone engages the correspondingly-shaped top inside surfaces of the slips when seated in the midsection and the top bonnet, to maintain the slips in proper functional orientation in the tubing head. A cylinder landing ring is seated in the midsection and lower body interface to limit downward travel of the rack cylinder. 
     As the downhole pressure in oil and gas wells decreases with time, it is sometimes desirable or necessary to insert tubing in the well to provide a mechanism for more readily removing fluids from the well and prolong the life of the well. Traditionally, it has been necessary to “kill” the well or terminate production by application of hydrostatic pressure in the well, to achieve this objective. A well is “killed” or production is terminated from the well, typically by pumping a fluid such as water into the producing interval to create a hydrostatic head of sufficient magnitude in the well to overcome the well pressure, thereby terminating production. One of the problems inherent in “killing” a producing well which has relatively low pressure, is the difficulty and sometimes impossibility, of restoring the well to production after the desired swabbing, cleaning or workover operation has been accomplished. These and other well maintenance operations are expensive, generally because of the time required to effect such steps as removing the “christmas tree”, setting up the necessary apparatus for maintaining the well, placing tubing in the well, (under circumstances where such tubing is deemed necessary), placing a tubing head on the master valve, setting the conventional, usually gravity-operated slip segments and the necessary packing, replacing the “christmas tree” and subsequently attempting to bring the well back into production. If the well cannot be brought back into production, then the time and money expended in the effort has obviously been wasted. 
     The use of coiled tubing as an alternative to running a production tubing string has received increased attention through the years. Under circumstances where the coiled tubing can be manipulated in a tubing hanger and anchor assembly which is compatible with the needs of the operator, many of the well operating objectives can be accomplished. This is especially true under circumstances where the coiled tubing is designed to keep marginal wells unloaded. For example, the coiled tubing can be used as a cycling string to delay or replace the need for much more expensive or less efficient forms of artificial lift. Furthermore, the coiled tubing can be secured in the slip bowl of the coiled tubing anchor assembly with a close tolerance and can be quickly and easily adjusted up or down, as desired. Other advantages of running coiled tubing in the place of conventional tubing strings in wells will be hereinafter apparent. 
     2. Description of the Prior Art 
     Gravity-operated slip assemblies and related equipment of various design have long been employed in the oilfield for suspending pipe and tubing in oil and gas wells. Such assemblies usually consist of multiple, segmented wedges which are tapered and are provided with horizontally-extending teeth located on curved inner surfaces, which teeth are designed to engage and cut into the pipe or tubing to prevent relative movement between the tubing and the slips. The slips usually include several segments which together conform to a tapered, usually conical slip bowl provided in a tubing head and facilitate engagement of the slips by gravity radially about the pipe or tubing when the slips are released inside the slip bowl responsive to contact between the tapered outside surfaces of the slips and the slip bowl in the tubing head. Lowering of the pipe or tubing after release of the slips results in a radial compressive force which urges the segment teeth against the pipe or tubing until the teeth cut into the pipe or tubing wall sufficiently to support the weight of the tubing in the tubing head. The teeth provided in the curved inner face of each slip segment are configured and oriented to engage and cut into the pipe or tubing in an optimum manner, in order to prevent relative movement between the slip segments and the suspended pipe or tubing. 
     Various devices have long been known in the prior art for supporting casing and tubing in oil and gas wells. An early “Casing Head” is detailed in U.S. Pat. No. 1,400,940, dated Dec. 20, 1921, to C. S. Clarke. The Clarke device includes a clamping member which is adapted to grip a pipe by wedging into engagement with the pipe, responsive to the weight of the pipe. A “Safety Clamp For Diamond Drill Rods” is detailed in U.S. Pat. No. 1,458,906, to N. W. Morisette. The device includes a clamp device having a housing fitted with a sliding element having teeth and a rotating clamping apparatus that selectively engages the teeth to clamp a workstock extending through a bore defined by the teeth. U.S. Pat. No. 1,575,998, dated Mar. 9, 1926, to W. H. McKissick, details a “Tubing Spider” which includes an annular carrier from which slips are suspended, with an operating mechanism for elevating the carrier, such that the slips are retracted into the body of the spider relatively outwardly of the depending guide flange into selective contact with tubing extending through the device. U.S. Pat. No. 2,071,637, dated Feb. 23, 1937, to M. P. Laurent, details a “Slip” characterized by a bushing shaped to fit within a rotary table and a downwardly-tapered, circular seat in the bushing, along with multiple downwardly and inwardly-inclined slideways recessed into the seat of the bushing and slips having outer inclined faces fitting within the slideways, the inner faces of the slips also have a mortised recess opening at the top. An insert having a tenon thereon engages each of the recesses. U.S. Pat. No. 2,896,292, dated Jul. 28, 1959, to R. B. Kinzbach, details an “Automatic Tubing Spider Assembly” which includes a spider body formed with radially-disposed wings having recesses to receive corresponding, radially-movable gripping members pivotally carried on links which are pivotally secured to the spider body. The links are shaped in the configuration of cams provided in camming engagement with the gripping members and with the spider body, thus providing supporting connection between the gripping members and the spider body, as well as between the gripping members and the tubing, when the members sustain a load. U.S. Pat. No. 3,791,661, dated Feb. 12, 1974, to Charles E. Giles, details a “Collet and Collet Fixture”. The collet and collet fixture allows an adjustment in the height of a workpiece held in the collet. The collet is locked into position from the bottom by the fixture, providing a secure positioning of the collet and accurate machining of the workpiece. Other patents detailing typical slip-operated tubing head designs are U.S. Pat. No. 3,287,035, dated Nov. 22, 1966, to Greenwood; U.S. Pat. No. 4,334,342, dated Jun. 15, 1982, to Hall; U.S. Pat. No. 4,326,587, dated Apr. 27, 1987, to Gauthier, et al; U.S. Pat. No. 4,554,971, dated Nov. 26, 1985, to Cobb; and U.S. Pat. No. 4,646,827, dated Mar. 3, 1989, also to Cobb. 
     It is an object of this invention to provide a new and improved tubing hanger assembly for suspending tubing in an oil or gas well using a mechanically-assisted slip assembly to selectively engage and disengage the tubing. 
     Another object of this invention is to provide a tubing hanger assembly for running tubing, and coiled tubing in particular, in an oil or gas well, which assembly is characterized by multiple, bevelled, collectively conical slip segments loosely connected by a retainer ring and mounted in the correspondingly conical throat of a tubing head. A rack element such as a cylindrical rack cylinder is located in the tubing head beneath the slips and is fitted with teeth or lands and grooves engaged by a pinion gear attached to a slip-operating mechanism, for selectively manipulating the cylinder and the slips upwardly and downwardly in the tubing head and facilitating controlled engagement and release of the slip segments in the slip bowl of the tubing head with tubing placed in the well. 
     Another object of this invention is to provide a new and improved coiled tubing hanger assembly for use in a specially designed tubing head to suspend coiled tubing in oil and gas wells, typically without “killing” the wells, which hanger assembly includes as the first element, multiple, tapered slip segments clustered in a slip assembly by a retainer ring and disposed in the tapered slip bowl of the tubing head, a cylindrical rack cylinder located in the tubing head beneath the slip segments and engaging the slip segments, teeth or lands and grooves provided on the rack cylinder for engagement by a pinion gear attached to an externally-projecting slip-operating mechanism, to facilitate selective rotation of the pinion gear by manipulation of the slip-operating mechanism, raising and lowering the rack cylinder and the slips in the tubing head and controlled engagement and disengagement of the coiled tubing by the slips. 
     A still further object of this invention is to provide a coiled tubing hanger assembly for running coiled tubing in a well, which assembly includes a specially designed tubing head having a bonnet, a midsection and a lower body, with a tapered or conical throat provided in the midsection for accommodating multiple, tapered slips assembled in a correspondingly conical configuration on a slip retainer ring and seated on a cylindrical rack cylinder located in a midsection bore communicating with the tapered throat, the rack cylinder having lands and grooves engaged by a pinion gear attached to a slip-operating mechanism. Manual manipulation of the slip-operating mechanism effects selective raising and lowering of the rack cylinder and the slips in the midsection bore and tapered throat, respectively, and selective engagement and disengagement of the slip teeth with the coiled tubing extending through the tubing head adjacent to the slip teeth. A pack-off assembly in the lower body prevents well pressure from interfering with operation of the coiled tubing hanger assembly. 
     SUMMARY OF THE INVENTION 
     These and other objects of the invention are provided in a new and improved coiled tubing anchor assembly which, in a preferred embodiment, is characterized by multiple, collectively conically-shaped slip segments positioned in the slip bowl of the midsection of a tubing head, each of the slip segments provided with slip teeth and bevelled or tapered outer surfaces for engaging a correspondingly tapered or conical throat in the midsection. The slip segments are constrained to move vertically in concert in the tapered throat of the midsection by means of a retainer ring and are seated on a rack cylinder having lands and grooves and also vertically and slidably disposed in the midsection bore. The teeth of a pinion gear engage the rack cylinder lands and grooves and the pinion gear is mounted on a slip screw that extends through the wall of the midsection to an external lever or slip screw in the slip-operating mechanism, such that manual manipulation of the lever or slip screw rotates the pinion gear and raises and lowers the rack cylinder and the slips for selectively engaging and disengaging the slip teeth with the coiled tubing extending through the tubing head and into the well. In a preferred embodiment the tubing head further includes a bonnet, typically bolted to the top of the midsection and a lower body bolted to the bottom of the midsection, which lower body includes a packing assembly for sealing the suspended tubing from well pressure. A slip cone is also provided in the bonnet for limiting upward movement of the slips and a cylinder landing ring is seated in the midsection-lower body interface for limiting the downward travel of the rack cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood by reference to the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a preferred embodiment of the assembled coiled tubing hanger assembly of this invention; 
     FIG. 2 is an exploded view of the coiled tubing hanger assembly illustrated in FIG. 1; 
     FIG. 3 is a perspective exploded view of the lower body element of the coiled tubing hanger assembly illustrated in FIGS. 1 and 2, more particularly illustrating internal pack-off assembly elements and a preferred pack-off screw and packing design; 
     FIG. 4 is an exploded view of the midsection element of the coiled tubing hanger assembly and the respective internal slip cone, slip assembly rack cylinder landing ring and slip operating mechanism elements for seating in the midsection; 
     FIG. 5 is a longitudinal sectional view, taken along line  5 — 5  of the assembled coiled tubing hanger assembly illustrated in FIG. 1; 
     FIG. 6 is a sectional view, taken along line  6 — 6  of the midsection element of the tubing head illustrated in FIG. 2; 
     FIG. 7 is a sectional view of a preferred embodiment of the slip-operating mechanism; and 
     FIG. 8 is a perspective view of a partially assembled slip assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to FIGS. 1,  2  and  5  of the drawings, a preferred embodiment of the coiled tubing hanger assembly of this invention is generally illustrated by reference numeral  1  and is characterized by a tubing head  2 , which includes a top bonnet  3 , bolted to the top of a midsection  8 , the bottom of which midsection  8  is, in turn, bolted to a lower body  34 . The top bonnet  3  is characterized by a bonnet bore  3   b , internally-threaded top bonnet apertures  3   a  and bottom bonnet apertures  4 , the latter of which receive threaded studs  14 , extending through midsection stud apertures  9  of the midsection  8  and secured in place by means of stud nuts  14   a . The lower body  34  is likewise attached to the bottom of the midsection  8  by means of additional threaded studs  14 , which project through lower body stud apertures  35  and engage the internally threaded midsection apertures  9   a  and are secured by companion stud nuts  14   a . A midsection access  8   a  and a lower body access  34   a  facilitate wrench access to the respective stud nuts  14   a , as necessary. The bonnet ring gasket groove  5  and opposed top midsection ring gasket groove  10  accommodate a ring gasket  6  to seal the top bonnet  3  in place on the midsection  8 , as further illustrated in FIG.  5 . In like manner, the lower one of the midsection ring gasket grooves  10  is aligned with the lower body ring gasket groove  36  and accommodates a second ring gasket  6 , to seal the midsection  8  on the lower body  34 . A slip cone seat  7  is machined in the bottom face of the top bonnet  3  inside the bonnet ring gasket groove  5 , for receiving the top edge of the slip cone flange  16  of a slip cone  15 , having a downwardly-extending slip cone base  17 . 
     A midsection slip bore  11  is provided in the midsection  8  as illustrated in FIG. 4, and communicates with the bonnet bore  3   b  of the top bonnet  3 . In a preferred embodiment of the invention, the midsection slip bore  11  tapers from a large diameter at the top thereof to a smaller diameter at the bottom, to define a tapered or conical throat  12 , as further illustrated in FIGS. 5 and 6. A midsection rack cylinder bore  13  communicates with the bottom end of the midsection slip bore  11  at the base of the tapered throat  12  and extends downwardly to communicate with the lower body bore  38  and the smaller exit bore  42 , of the lower body  34 . A lower body outlet  37  is also provided in the lower body  34  for circulating fluid to and from the well without the necessity of pumping the fluid through the tubing head  2 . Lower body mount apertures  34   b  are provided in the lower body  34  for attaching the lower body  34 , and thus the tubing head  2 , to the conventional well head equipment (not illustrated) of a well (also not illustrated). 
     Referring now to FIGS. 4-6 and  8  of the drawings, a slip assembly  18  includes multiple slips  19 , each of which have tapered, rounded outer surfaces  23 , that terminate in cylinder-engaging edges  25  and collectively define a cone that matches the tapered or conical throat  12  in the midsection  8 . Curved inner teeth  24  are provided on the slips  19 , below inner arcuate cone base seats  22 , for selectively engaging a length of tubing  52 , extending through the tubing head  2 , as hereinafter further described. The tapered, rounded outer surfaces  23  of the slips  19  engage the tapered throat  12  of the midsection slip bore  11  to facilitate slidable opening and closing of the respective slips  19  in concert, which opening and closing action is loosely orchestrated by a split slip retainer ring  21 , extending through corresponding and aligned retainer ring slots  20  in each of these slips  19 , as further illustrated in FIGS. 6 and 8. The inner cone base seats  22  are configured to the shape of the slip cone base  17  of the slip cone  15 , as illustrated in FIGS. 5 and 6. The top margins  19   a  of the slips  19  are designed to contact the slip cone flange  16  when the slips are in fully disengaged upwardly-extended configuration. Accordingly, it will be appreciated by those skilled in the art that upward movement of the slips  19  in the tapered throat  12  of the midsection slip bore  11  causes the slips  19  to diverge from each other and from the tubing  52  and the slip cone base  17  and toward the slip cone flange  16  in disengaged configuration, and the slips  19  converge into engagement with the tubing  52 , when moving downwardly in the tapered throat  12 , as the slips  19  operate in concert due to the action of the slip retainer ring  21 . 
     As further illustrated in FIGS. 5-7, a rack cylinder  27  is slidably sealed by means of O-rings  31 , seated in O-ring seats  31   a , in the midsection rack cylinder bore  13 , which extends beneath and communicates with the tapered throat  12  area of the midsection slip bore  11 . In a preferred embodiment the rack cylinder  27  is fitted with alternating lands  28  and grooves  29  and has a longitudinal cylinder bore  30 , which accommodates the tubing  52  extending through the slips  19  adjacent to the slip teeth  24 . The top of the rack cylinder  27  engages the cylinder engaging edges  25  of the slips  19  when the slips  19  are in diverging, disengaging configuration and the gear teeth  47   a , provided on a pinion gear  47  element of a slip-operating mechanism  43 , engage the lands  28  and the grooves  29  of the rack cylinder  27 , as further illustrated in FIGS. 6 and 7. The pinion gear  47  is attached by welding or otherwise, to a pinion gear mount  54 , extending from the operating end of a slip screw  45 , having slip screw threads  46  that are threaded into a gear access opening  47   b  in the midsection  8 . In one embodiment of the invention an external screw lever  44  is attached, typically by means of one or more allen screws  57  (FIG.  4 ), to the opposite end of the slip screw  45  from the pinion gear  47 , to facilitate rotation of the slip screw  45  and the pinion gear  47  and effect vertical adjustment of the rack cylinder  27  and thus, the slips  19 , in the midsection rack cylinder bore  13  and the midsection slip bore  11 , respectively, (FIGS. 1,  2 ,  4  and  6 .) In a preferred embodiment illustrated in FIG. 7, a wrench nipple  58  is shaped on the projecting end of the slip screw  45  for operating the pinion gear  47  without a screw lever  44 . In this embodiment, a typically metal ring  56  is secured to the slip screw  45  by one or more allen screws  57  and an indicator  60  is typically welded or otherwise attached to the ring  56  for engaging a pair of cap screws  59 , threaded in in the midsection  8  at the selected extremes of rotation of the slip screw  45  and the pinion gear  47 , to act as stops. An indicator  60  is also preferably mounted on the lever  44  of the slip-operating mechanism embodiment illustrated in FIGS. 1,  2 ,  4  and  6 , for engaging a pair of likewise positioned cap screws  59 . A gland nut  48  is threaded in a threaded seat  26 , provided in a slip screw recess  45   a  in the wall of the midsection  8  and includes a pair of junk rings  49 , between which gland nut packing  50  is positioned, to seal the slip screw  45  in the midsection  8  against well pressure. 
     Referring now to FIGS. 3,  4  and  5  of the drawings, a pack-off assembly  33  is provided in the enlarged lower body bore  38  of the lower body  34 , beneath the cylinder landing ring  32 , located at the base of the midsection rack cylinder bore  13 . The cylinder landing ring  32  provides a downward stop for movement of the rack cylinder  27 . A top pack-off plate  39 , having a plate taper  39   a , is located in the lower body bore  38  immediately beneath the cylinder landing ring  32  and pack-off seals  40  are provided in the lower body bore  38 , between the top pack-off plate  39  and a bottom pack-off plate  41 , seated in the bottom end of the lower body bore  38 . Pack-off screws  51 , having bevelled faces  51   a  and screw threads  51   b , are threaded in radially disposed relationship in the lower body  34 , to selectively engage the plate taper  39   a  of the top pack-off plate  39 , tighten the top pack-off plate  39  against the pack-off seals  40  and seal the tubing head  2  from well pressure. 
     In operation, referring again to the drawings, under circumstances where it is desired to insert a length of tubing  52  into a well without reducing the pressure or “killing” the well, the master valve (not illustrated) in a conventional “christmas tree” (also not illustrated) is initially closed. The “christmas tree” is then removed from the master valve in conventional fashion and the tubing head  2  is installed on the master valve in place of the “christmas tree”, by inserting bolts or studs (not illustrated) through the master valve flanges and threading the bolts or studs into the lower body mount apertures  34   b  of the lower body  34 , illustrated in FIGS. 4 and 5. The slips  19 , which have been loosely assembled in a slip retainer ring  21  to define the slip assembly  18 , as illustrated in FIGS. 6 and 8, are then displaced upwardly in concert by upward adjustment of the rack cylinder  27  responsive to manipulation of the lever  44  or application of a wrench (not illustrated) to the wrench nipple  58  (FIG.  7 ), which rotates the slip screw  45  and the pinion gear  47  and causes the pinion gear  47  to traverse the lands  28  and grooves  29  of the rack cylinder  27 . As the slips  19  extend upwardly in concert as a slip assembly  18  in the midsection slip bore  11 , the tapered outer surfaces  23  of the slips  19  slide upwardly along the tapered throat  12  of the midsection  8  and the slips  19  diverge from each other and from the slip cone base  17 , toward the slip cone flange  16 , while orchestrated by the retainer ring  21 . When fully open in disengaged configuration, the top margins  19   a  of the slips  19  typically contact the slip cone flange  16  of the slip cone  15 , as illustrated in FIG.  6 . This action facilitates retraction of the slip teeth  24  in a radial direction to facilitate insertion of the tubing  52  through the bonnet bore  3   b  of the top bonnet  3 , the slip assembly  18 , the midsection slip bore  11  and the cylinder bore  30  of the rack cylinder  27 , the midsection rack cylinder bore  13  and through the top pack-off plate  39 , the pack-off seals  40  and the bottom pack-off plate  41  and finally, through the exit bore  42  of the lower body  34 , into the well. 
     Accordingly, the tubing  52 , which is typically coiled tubing wound on a drum (not illustrated) positioned in cooperation with a tubing running unit (also not illustrated) designed to insert the tubing  52  in a well, is then positioned near the well location and in a typical operating set-up the tubing head  2  is seated on a valve and typically, “a christmas tree” combination (not illustrated). An appropriate blowout preventor system (further not illustrated) is then mounted on the top bonnet  3  of the tubing head  2  in association with the tubing  52 , typically by bolts or studs threaded into the top bonnet apertures  3   a , according to procedures well known to those skilled in the art. The tubing running unit is then set up for inserting one end of the tubing  52  into the well through the blowout preventors and the tubing head  2  as indicated above, and the well is subsequently “packed off” or sealed above the blowout preventors in conventional fashion, to prevent the working pressure in the well from escaping around the tubing  52  when the tubing  52  is inserted in the tubing head  2 . Before insertion, the inserted end of the tubing  52  is typically closed by means of a plug and the plugged end of the tubing  52  is extended through the tubing head  2  as described above, to the closed master valve. The packing in the tubing running unit is then tightly compacted in conventional fashion, the master valve is opened and the tubing  52  is then unwound from the drum and extended into the well to the desired depth. 
     When the tubing  52  has been inserted in the well to the desired depth and while it is supported by the tubing running unit, the slip assembly  18  is activated by operation of the lever  44  or the wrench nipples  58  in the slip-operating mechanism  43 , and rotation of the slip screw  45  to rotate the gear teeth  47   a  of the pinion gear  47  in the lands  28  and grooves  29  of the rack cylinder  27  and lower the rack cylinder  27  and the slip assembly  18  in the midsection slip bore  11 . This action causes the slips  19  to converge in the tapered throat  12  of the midsection slip bore  11 , since the slip taper  23  of each of the slips  19  engages the tapered throat  12  and causes the respective slip teeth  24  of the slips  19  to engage the tubing  52 , as illustrated in FIG.  5 . The slip-operating mechanism  43  is then operated to lower the rack cylinder  27  from the tapered throat  12 , fully into the non-tapered area of the midsection rack cylinder bore  13 , to prevent interference with operation of the slips  19 . 
     In a preferred embodiment of the invention the slip-operating mechanism  43  is so designed that a one-quarter to one-half turn of the slip screw  45  by manipulation of the lever  44  will effect sufficient vertical movement of the rack cylinder  27  to facilitate full movement of the slips  19  from disengagement of the slip teeth  24  with the tubing  52 , to engagement with the tubing  52 . However, it is understood that the degree of rotation is determined by the size and spacing of the lands  28  and grooves  29  on the rack cylinder  27  and the diameter of the pinion gear  47 , together with the spacing of the gear teeth  47   a . The cap screws  59  (FIGS. 1,  2  and  7 ) are typically located at the required extremes of rotation for engagement by the indicator  60 , as heretofore described. The slip assembly  18  is now in position such that the tubing  52  cannot deploy further into the well and regardless of the weight of the tubing  52  extending into the well, the tubing  52  will not slip from the engaged position illustrated in FIG.  5 . When the slips  19  are properly positioned in the tapered throat  12  of the midsection slip bore  11  such that the respective slip teeth  24  securely engage the tubing  52 , the tubing running unit is adjusted to reduce the supporting force on the tubing  52  and as the weight of the tubing  52  in the well is brought to bear on the slip teeth  24  of the slips  19 , the slip teeth  24  penetrate the outer surface of the tubing  52  and the slip assembly  18  securely supports the tubing  52  in the well without slippage. The pack off screws  51  are then rotated in the clockwise direction to cause the bevelled faces  51   a  to exert pressure on the plate taper  39   a  of the top-bevelled top pack-off plate  39 , which action tightens the pack-off seals  40  located between the top pack-off plate  39  and the bottom pack-off plate  41 , and securely seal the tubing  52  in the tubing head  2  against well pressure. When this sealing is accomplished, the tubing  52  is considered to be “packed off” in the tubing head  2  and the pressure of the well is tested above the tubing head  2  to insure that the pack-off seals  40  located between the top pack-off plate  39  and the bottom pack-off plate  41  are holding the well pressure. The tubing running unit and the blowout preventors may then be removed from the tubing head  2  and the tubing  52  is typically cut at a point about six inches above the tubing head  2 , a second valve is flanged to the top bonnet  3  of the tubing head  2  using the top bonnet apertures  3   a  in conventional fashion and the bottom valve becomes the master valve. Flow or production lines are then reattached as required, and nitrogen is typically pumped through the “christmas tree” into the open end of the tubing  52  to remove the plug from the opposite end of the tubing  52 , which extends into the well. The well is then ready to produce hydrocarbons through the exit bore of the lower body outlet  37  located in the lower body  34 , and through the tubing bore of the tubing  52 , as desired. 
     Referring again to FIG. 5 of the drawings, it will be appreciated by those skilled in the art that the slip assembly  18  and the rack cylinder  27  can be easily accessed from the interior of the midsection  8  by removing the top bonnet  3  as the respective stud nuts  14   a  are removed from the companion studs  14 . This action clears the slip cone  15  for easy removal from the midsection slip bore  11  and facilitates removal of the slip assembly  18  as a unit from the tapered throat  12 . When the slip assembly  18  is thusly removed, the rack cylinder  27  may then be engaged by a tool suitable for the purpose and extended from the midsection rack cylinder bore  13 , after the pinion gear  47  is removed with the slip-operating mechanism  43  through the gear access opening  47   b , by unthreading the gland nut  48 , to clear the gear teeth  47   a  from lands  28  and grooves  29  of the rack cylinder  27 . Accordingly, it will be appreciated by those skilled in the art that replacement of the slip cone  15 , the slips  19  and the slip assembly  18 , as well as the rack cylinder  27 , is easily accomplished on the job in this manner for maintenance purposes. Replacement or repair of the pack-off assembly  33  is effected by removing the stud nuts  14   a  from the studs  14  that secure the midsection  8  to the lower body  34 , as illustrated in FIG.  5 . Secure sealing of the slip screw  45  and the pack-off screws  51  in the midsection  8  against well pressure is accomplished by tightening the respective gland nuts  48 , squeezing the packing  50 , in conventional manner. 
     It will be further appreciated by those skilled in the art that the coiled tubing hanger assembly of this invention is versatile and offers many advantages over prior art equipment for inserting tubing and coiled tubing in particular, in an oil or gas well. Since the working pressure of the well does not need to be neutralized in order to insert the tubing in the well, there is therefore no necessity for using a workover rig or relying on special tools and equipment. Furthermore, a coiled tubing hanger assembly can be used to place tubing in the well under pressure and under circumstances where terminating pressure might cause permanent loss or production, where the only alternative to effect continued production is use of a pumping unit, sucker rod string and downhole pump. The coiled tubing hanger assembly of this invention can be used on wells of substantially any depth to support tubing under circumstances where the use of such tubing is feasible. Furthermore, since the use of the coiled tubing hanger assembly of this invention results in faster, more efficient insertion of tubing in a well, the operation is rendered safer and less expensive due to the reduced time of exposure to the well by the operators. An added positive feature is the capability of re-working the coiled tubing hanger assembly of this invention in the field according to the procedure outlined above without the necessity of removing the tubing head and taking it to a shop for the necessary maintenance and repairs. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.