Abstract:
A high-pressure packoff apparatus and method are disclosed. The packoff allows wireline entering a top drive drilling head through a top entry access system to be isolated in such a fashion to minimize the leakage and escape of drillstring fluids to the atmosphere. Optionally, an extension housing containing a flow tube assembly can be employed to accomplish the task. The flow tube assembly effectuates a pressure drop along the wireline conduit run therethrough, thus minimizing the likelihood of fluid escaping.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention claims the benefit of U.S. Provisional Application Ser. No. 60/481,659 filed Nov. 18, 2003 by Vernon Kauffman and Dwight LeBlanc, entitled “High Pressure Wireline Top-Entry Packoff Apparatus and Method,” hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to an apparatus for use on a drilling rig; specifically to a high-pressure wireline packoff seal apparatus for use on top-drive drilling rigs and the methods of using the same. 
         [0003]    The majority of large oil well drilling rigs operating throughout the world now use top-drive units to speed the assembly of drill string and to permit rapid, almost continuous, drilling. Wireline operations required on deep wells using these expensive rigs can be a severe bottleneck if they cannot be carried out with the expediency and efficiency sought by all drilling contractors. To remedy the problem of inserting a wireline through a top-drive unit, a top-entry apparatus providing a safe and effective means of inserting and manipulating a wireline in a top-drive unit has been developed. Top entry systems offer oilfield companies the opportunity to perform certain types of wireline operations under elevated drilistring bore and annulus pressures. Such wireline operations include, but are not limited to, pipe recovery, backoff, formation evaluation, and directional drilling operations. Because of the various requirements and measurements recorded during some of these wireline operations, it is often necessary to maintain this elevated pressure before, during, and after their commencement. 
         [0004]    There presently exists an important and long-felt need for a hydraulic packoff system and method with a top drive, top entry, wireline operations scheme that will allow operations to continue without reducing drilistring pressures. In order to accomplish this, a high quality seal mechanism is desired. Such a seal would enable the wireline to communicate with the drillstring bore while allowing the escape or leakage of only minimal amounts of bore fluids. The various embodiments of the present invention all address this particular need. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The deficiencies of the prior art are addressed by a top entry access system including a hydraulic packoff to allow a conduit into a bore of a drillstring. The hydraulic packoff preferably includes a main body wherein the main body preferably has a lower connection, a seal bore, an upper connection, and a mounting surface. The lower connection is preferably configured to attach to an inlet of the drilistring and the seal bore is preferably configured to receive a gland assembly. Preferably, the seal gland assembly is configured to allow the conduit to communicate with the bore of the drillstring without releasing drilling fluids therefrom. Preferably, the mounting surface of the main body is configured to receive and secure the top entry access system thereupon. 
         [0006]    The deficiencies are also addressed by a hydraulic packoff for a top drilling assembly wherein the packoff includes a main body having a lower connection, a seal bore, and a roller assembly. Preferably the seal bore is configured to receive a seal gland assembly with the seal gland configured to allow a conduit to communicate with a bore of a drillstring without releasing drilling fluids therefrom. Preferably, the roller assembly is positioned above and configured to guide the conduit into the gland assembly. 
         [0007]    The deficiencies can also be addressed by a hydraulic packoff for a top drilling assembly wherein the packoff includes a main body having a lower connection, a seal bore, and a retaining nut. Preferably the seal bore is configured to receive a seal gland assembly with the seal gland configured to allow a conduit to communicate with a bore of a drillstring without releasing drilling fluids therefrom. Preferably, the retaining nut is configured to compress the gland assembly. 
         [0008]    The deficiencies are further addressed by a method for entering a conduit into a drillstring driven by a top drive assembly wherein the method preferably comprises connecting a hydraulic packoff and an extension housing to a drillstring inlet above the top drive assembly. Preferably, the method also includes installing a flow tube assembly inside a bore of the extension housing and connecting a top entry access system above the hydraulic packoff. The method includes routing the conduit from a supply, through the top entry access system, into the hydraulic packoff, through the hydraulic packoff, through the flow tube assembly, through the drillstring inlet and into the drillstring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more detailed description of the preferred embodiments of the present invention, reference will not be made to the accompanying drawings, wherein: 
           [0010]      FIG. 1A  is a sectioned profile view drawing of a wireline packoff apparatus in accordance with the present invention installed in conjunction with a top entry access system. 
           [0011]      FIG. 1B  is a sectioned side view drawing of the wireline packoff apparatus shown in  FIG. 1A . 
           [0012]      FIG. 2  is a sectioned view drawing of a wireline packoff apparatus in accordance with the present invention installed in conjunction with an alternate top entry access system. 
           [0013]      FIG. 3  is a cross-sectional drawing of a wireline packoff apparatus in accordance with a first preferred embodiment of the present invention. 
           [0014]      FIG. 4  is a cross-sectional drawing of a wireline packoff apparatus in accordance with a second preferred embodiment of the present invention. 
           [0015]      FIG. 5  is a cross-sectional drawing of a wireline packoff apparatus in accordance with a third preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring initially to  FIGS. 1A-1B , a high-pressure packoff  10  enables a wireline conduit  20  to enter a bore of a drillstring (not shown) from a top entry access system  12  above an oilfield top-drive assembly (not shown). While conduit  20  is preferably constructed as a high tensile strength jacketed electrical conductor, it should be understood by one of ordinary skill in the art that any flexible oilfield communication conduit can be used with the various embodiments of the present invention. Examples of such conduits can include, but are not limited to, single or multiple electrical conductor wireline, fiber optic cable, braided steel cable, coiled tubing, and slickline. 
         [0017]    Top entry access system  12  typically includes a pair of large diameter sheave wheels  16 ,  17  between two plates  18 ,  19  but can be of any other configuration known to one skilled in the art. For example, referring briefly to  FIG. 2 , an alternative top entry access system  12 A is shown. Alternative access system  12 A includes a single large diameter sheave wheel  16 A at its top but instead of a lower sheave wheel, has a plurality of small-diameter rollers  22  to guide conduit  20  into location. Furthermore, alternative access system  12 A also includes a structural support bar  24  to rigidly secure system  12 A to lifting bales  26  and to prevent flexure. For examples of top entry access and top-drive systems entry, see U.S. Pat. No. 5,735,351 entitled “Top Entry Apparatus and Method for a Drilling Assembly” issued to Charles M. Helms on Apr. 7, 1998 and U.S. patent application Ser. No. 10/249,033 entitled “Universal Top-Drive Wireline Entry System Bracket and Method” filed on Mar. 11, 2003 by Kauffman, et al, both hereby incorporated herein by reference. 
         [0018]    Returning again to  FIGS. 1A-1B , packoff  10  is preferably situated between entry access system  12  and a manifold  14  located above the top drive assembly. Manifold  14  preferably includes a first inlet  28  to allow the entry of conduit  20  into the drillstring bore, and a second inlet  30  to allow the entry and pressurization of fluids into the drillstring bore. Manifold  14  is shown with a threaded connector  32  to allow attachment to the top drive assembly. Packoff  10  is preferably constructed to isolate the pressurized bore of drillstring from the atmosphere while still allowing the insertion and removal of conduit  20  in and out thereof. Furthermore, packoff  10  is preferably constructed to allow rotational movement of top entry access system with respect to manifold  14  and top drive assembly without compromising the sealing mechanism of packoff  10 . Finally, packoff  10  is preferably constructed as a robust device, one that will not fail under bending and torsional loading from top entry access system  12  through manipulation of conduit  20 . 
         [0019]    Referring now to  FIG. 3 , a packoff  50  assembly in accordance with a first preferred embodiment of the present invention is shown in more detail. Packoff assembly  50  is shown having a main body  52 , a gland assembly  54 , and a roller assembly  56 . Main body  52  preferably includes an outer journal surface  58 , a thrust surface  60 , an internal seal bore  62 , a bottom threaded connection  64 , and an upper threaded connection  66 . Surfaces  58 ,  60  are preferably provided to receive the connecting top entry access system that is mounted thereupon and provide a journal surface for rotational movement thereof of and a thrust surface for axial loads therefrom. Depending on configuration, Journal surface  58  can be constructed either to allow rotation of access system  12  or not to allow such rotation. In circumstances where free movement of access system  12  is desired, journal surface  58  can be constructed as a journal bearing surface, one that would allow such movement. In other circumstances where the movement of access system  12  is preferred to be restricted, an ordinary journal surface  58  can be employed. Alternatively, Top entry access system can connect to other rigsite structures such as lifting bales or the top drive head itself. Internal seal bore  62  houses packoff gland assembly  54  that includes a bladder  68 , a split rubber  70 , and a line rubber  72 . Backup rings  74  are positioned at the top and bottom of bladder  68  and include o-ring seals  76 . Backup rings  74  and seals  76  help seal, isolate, and compress bladder  68 , and rubbers  70 ,  72  against wireline ( 20  of  FIGS. 1-2 ) run therethrough. 
         [0020]    At its bottom, packoff gland assembly  54  is held in place by a bottom plate  78  secured by a bottom lip  80  of main body  52 . Optionally, below bottom lip  80  of main body  52 , a pin insert  82  and sealing ring  90  can be installed with bolts  84  to help align packoff assembly  50  into position on top of top drive assembly. At its top, packoff gland assembly  54  is compressed and held into place with an upper retainer nut  86 . Upper retainer nut  86  has an outer threaded profile  88 , and an inner threaded profile  90 . Retainer nut  86  is installed by threading outer profile  88  into thread profile  66  of main body  52  until gland assembly  54  is properly compressed. Once retainer nut  86  is in position, a packoff safety cap  94  is installed and secured with bolts  96 . 
         [0021]    Above main body  52  roller assembly  56  is optionally installed. Roller assembly  56  preferably includes roller body  98 , a plurality of rollers  100 , a bushing  102 , and a bushing cage  104 . Rollers  100 , mounted at the top of roller body  98  and secured with bearing pins  106  and cotter keys  108 , smoothly guide wireline  20  into the main body  52  and through the gland assembly  54 . A threaded profile  110  is located at the bottom of roller body  98  and corresponds with internal threaded profile  90  to engage roller assembly  56  into upper retainer nut  86 . Bushing  102 , preferably constructed of brass or any other standard bushing material, acts in conjunction with bushing cage  104  to compress and hold line rubber  72  in place. 
         [0022]    Wireline conduit  20  enters packoff assembly  50  of  FIG. 3  at rollers  100 , travels through bushing  102  to line rubber  72  and out through bottom plate  78  and pin insert  82  and into top drive drilling head assembly. A lubrication channel  112  is preferably pressurized with lubrication oil or other suitable lubricating fluid to help maintain the sealing of wireline  20 . Seals  77 ,  90 , and bladder  68  maintain the isolation of lubrication channel  112  from the atmosphere. 
         [0023]    Referring now to  FIG. 4 , a packoff assembly  120  in accordance with a second preferred embodiment of the present invention is shown. Packoff assembly  120  is shown similarly to packoff assembly  50  of  FIG. 3 , but with the inclusion of an extension housing  122  and a flow tube assembly  124 . As with assembly  50  of  FIG. 3 , packoff assembly  120  includes a main body  126  and a gland assembly  128 . Main body  126  includes upper and lower threaded profiles  130 ,  132 , an outer bearing surface  134 , and a bore  136  to receive gland assembly  128 . Gland assembly  128  is held in place with a gland retainer nut  138  but a seal retainer  140  holds gland assembly  128  in compression rather then a bushing and roller assembly ( 102  and  56  of  FIG. 3 ). Extension housing  122  includes an upper threaded profile  142 , a lower mating pin  144 , a receptacle bore  146 , and a threaded securing nut  148 . Extension housing  122  is installed upon the wireline entry inlet  28  of manifold  14 , located just above the top drive assembly (not shown). While one embodiment of extension housing  122  is shown, it should be understood by one of ordinary skill in the art that housing  122  can be constructed in many different manners without departing from the spirit of the invention. Particularly, extension housing can be constructed integral to main body  52  of packoff assembly  50  (or  120 ), while maintaining the same characteristics of housing  122  shown in  FIGS. 4 and 5 . 
         [0024]    Extension housing  122  allows for the installation of flow tube assembly  124  to help reduce the bore fluid pressure acting on wireline conduit  20  as it exits gland assembly. Flow tube assembly  124  includes a plurality of expansion cavities  150  that extend around wireline  120  from the bottom to the top of flow tube  124 . A fluid port  152  is connected to a main cavity  154  of flow tube  124  and is used to remove pressurized bore fluids from around wireline  20 . Because of elevated borehole pressures, flow tube assembly  124  needs to be held in place inside housing  122  with a nut or a c-ring (not shown). Otherwise, sudden elevations in bore pressure could cause flow tube assembly  124  to “blow out” of its seat in housing  122 . 
         [0025]    As pressurized fluids flow from bottom of flow tube  124  to main cavity  154  the pressure is incrementally dropped after experiencing each cavity  150 . Finally, fluids are siphoned off at port  152  to further effectuate the pressure drop, resulting in a fluid pressure at gland assembly  128  that is significantly lower than the fluid pressure at the top drive drilling assembly. This reduced pressure at gland assembly  128 , allows for the insertion and removal of wireline conduit  20  from the drilling assembly with little or no escaping bore fluids. While a particular construction for flow tube assembly  124  is shown, it should be understood that various designs can be created and used by one skilled in the art. For instance, a flow tube with varying profiles and numbers of expansion cavities  150  can be used. The specific design and construction of flow tube assembly  124  will depend on variables such as bore pressure, the size of conduit  20 , and the amount and rate of pressure drop desired. The example shown is not meant to limit the design, configuration, and construction of flow tube assembly  124 , but is merely illustrative. 
         [0026]    Referring still to  FIG. 4 , one method of installing packoff assembly  120  with flow tube assembly  124  can be described. Extension housing  122  can first be installed atop entry inlet  28  of manifold  14  placing mating pin  144  into inlet  28  and tightening securing nut  148 . Securing nut  148  has internal threads  156  that correspond to mating outside threads  158  of inlet  28 . Furthermore, an o-ring  160  is positioned on the outside of mating pin  144  to prevent the leakage of fluids therefrom. With Extension housing  122  secured to manifold  14 , flow tube assembly  124  can then be inserted into the receptacle bore  146  of extension housing  144 . O-rings  162  on the outer surface of flow tube assembly  124  are lubricated and installed to prevent the fluids from bypassing the internal cavities  150 ,  154  of flow tube assembly  124 . 
         [0027]    Next, a length of wireline conduit  20  is released and fed through the gland assembly  128  and main body  126  and then fed through flow tube assembly  124 . With wireline conduit  20  pre-fed, main body  126  is threaded onto the upper threads  142  of extension housing  122  with corresponding lower thread profile  132 . When packoff assembly  120  is so assembled, Top entry access system  12  can then be secured to the outer bearing surface  134  of main body  126 . Preferably, upper threads  142  of extension housing  122  and mating outside threads  158  of inlet  28  are of the same design and construction. This way, if the flow tube assembly  124  is not needed for a particular operation, main body  126  can be threaded directly onto pin  28  without installing extension housing  122 , similar to assembly shown in  FIGS. 1-3 . 
         [0028]    Referring briefly to  FIG. 5 , a packoff assembly  220  in accordance with a third preferred embodiment of the present invention is shown. Packoff assembly  220  similar to packoff assembly  120  of  FIG. 4 , but with the addition of a roller body  298  to the top of main body  226 . Roller body  298  acts in a manner similar to roller body  98  of  FIG. 3  and helps guide wireline conduit  20  from top entry access system  12  into main body  226 , through flow tube assembly  224  and extension housing  222  and into entry inlet  28  of manifold  14 . As with extension housing  122  of  FIG. 4 , extension housing  222  is secured atop inlet  28  with a securing nut  248  that engages outer threads  258  of pin. Roller body  298  of  FIG. 5  would be installed atop gland assembly (not shown in  FIG. 5 ) in place of the retainer nut  138  shown in  FIG. 4 . Alternatively, roller body  298  could be secured to the top of retainer nut  138  by any means known by one of ordinary skill in the art. 
         [0029]    Numerous embodiments and alternatives thereof have been disclosed. While the above disclosure includes the best mode belief in carrying out the invention as contemplated by the named inventors, not all possible alternatives have been disclosed. For that reason, the scope and limitation of the present invention is not to be restricted to the above disclosure, but is instead to be defined and construed by the appended claims.