Abstract:
A rotatable head assembly wherein there is an outer housing that carries a cartridge assembly that permits rotational movement. The cartridge assembly made up of a cartridge housing and cartridge body that is rotatable within the cartridge housing. Static seals are used to provide fluid seals between the radially outer surface of the cartridge housing and the outer housing. Fluid passages within the cartridge housing carry lubricating fluid from the static seals to dynamic seals that allow the cartridge body to rotate easily within the cartridge housing. Fluid passages are also provided within the cartridge housing for carrying spent fluid out through the cartridge housing. There may be multiple fluid inlets and outlets within the cartridge housing without requiring a multiplicity of stepped increases in the diameter of the cartridge housing and the outer housing. Instead, the inlets and outlets are angularly spaced about the circumference of the cartridge, and each of the fluid passages extends axially through the cartridge housing to a different axial position, or elevation, along the body of the cartridge housing. The static seals also provide resilient and lasting fluid sealing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the priority of U.S. Provisional patent application Ser. No. 60/202,575 filed May 10, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to head assemblies including rotating head systems and the like. In particular aspects, the invention relates to methods and devices for sealing a rotating drilling head or other device having a rotatable bearing against a drill pipe or other tubular member.  
           [0004]    2. Description of the Related Art  
           [0005]    Rotating drilling head systems use an elastomeric element to seal the drilling head against a drill pipe during drilling operations. One of such systems is described in U.S. Pat. No. 6,016,880,entitled “Rotating Drilling Head with Spaced Apart Seals,” which has been assigned to the assignee of the present invention. That patent is incorporated herein by reference. Rotating drilling head arrangements typically use a cartridge unit that can be readily installed and removed from a housing for replacement of the elastomeric elements.  
           [0006]    The cartridge unit for the system of the &#39;880 patent is landed within a housing that contains several laterally oriented fluid flow ports through which lubricating fluid is pumped. The fluid ports on the housing are aligned with complimentary ports in the cartridge unit to form complete flow paths. The flow ports are sealed from one another using smaller diameter seals, each concentric with one of the flow ports. Unfortunately, if small diameter seals are used, they wear out quickly as replacements of the cartridge occur.  
           [0007]    Gallery seals work better than the small diameter elastomeric seals. However, to work properly, there must be stepped increases in the diameter of the main housing within which the cartridge unit resides. Too many of these diameter increases result in the cartridge unit being too large at the upper end, thereby requiring a larger main housing, which may be impractical. A cartridge unit and drilling string of smaller diameter can be used instead. However, this is generally considered to be undesirable as drilling productivity is reduced.  
           [0008]    The present invention addresses the problems of the prior art.  
         SUMMARY OF THE INVENTION  
         [0009]    The invention relates generally to head assemblies and like devices wherein there is an outer housing that carries a cartridge assembly that permits rotational movement. In particular aspects, the invention provides techniques for establishing an improved seal between the outer housing and the cartridge assembly. Additionally, the invention provides techniques for improved lubrication of the bearings used within the cartridge assembly. An exemplary rotating drilling head assembly is described that is representative of this type a head assembly and includes a cartridge assembly made up of a cartridge housing and cartridge body that is rotatable within the cartridge housing. In the preferred embodiment described, static seals are used to provide fluid seals between the radially outer surface of the cartridge housing and the outer housing. On or more fluid passages within the cartridge housing carry lubricating fluid from the static seals to dynamic seals that allow the cartridge body to rotate easily within the cartridge housing. One or more fluid passages and static seals are also provided so that spent fluid may be removed through the cartridge housing.  
           [0010]    The static seal arrangement of the present invention is advantageous, as compared to prior art techniques for providing sealing in these types of head assemblies. For example, there may be multiple fluid inlets and outlets within the cartridge housing without requiring a multiplicity of stepped increases in the diameter of the cartridge housing and the outer housing. Instead, the inlets and outlets are angularly spaced about the circumference of the cartridge, and the fluid passages extend axially through the cartridge housing to a different axial position, or elevation, along the body of the cartridge housing. The static seals also provide resilient and lasting fluid sealing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIGS. 1A and 1B are a cross-sectional side view of an exemplary rotating drilling head assembly constructed in accordance with the present invention.  
         [0012]    [0012]FIG. 2 is a schematic isometric view of the cartridge housing used in the drilling head assembly of FIG. 1 shown apart from the drilling head assembly.  
         [0013]    [0013]FIG. 3 is a detail cross-sectional view illustrating an exemplary static seal. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    The devices and methods of the present invention are applicable generally to head assemblies wherein an outer, generally cylindrical housing retains a cartridge assembly that provides for rotational motion. The cartridge assemblies in such devices typically include a stationary outer cartridge sleeve and an inner body that is rotatably mounted within the cartridge housing. Lubrication is used to permit ease of rotation for the cartridge body within the cartridge housing.  
         [0015]    [0015]FIGS. 1A and 1B depict an exemplary rotating drilling head arrangement  10  that is representative of head assemblies of the type mentioned above. The drilling head arrangement  10  includes a cartridge assembly  12  that is shown seated in a main housing  14 . The main housing  14  is typically mounted below the rig floor (not shown). The drilling head  10  is used in conjunction with drill pipe (not shown) having a plurality of tool joints. The tool joints are the threaded connector portions of each section of pipe and have enlarged outer diameters over the remaining portion of the pipe.  
         [0016]    The main housing  14  is generally cylindrical in shape. Proximate its upper end, the main housing  14  has two fluid inlet ports  16   a  (one shown) and two fluid outlet ports  18   a  (one shown). Further down along the length of the main housing  14  are three fluid inlet ports  16   b  (one shown) and two fluid outlet ports  18   b  (one shown) that pass through the housing  14 . The lower end of the main housing  14  has an annular groove  20  located above an outwardly protruding annular flange  22 . Apertures  24  are disposed through the flange  22  so that connectors (not shown) may be passed through the flange  22  to connect the main housing  14  to other components such as a mud sleeve. A mud outlet  23  and pressure sensor  25  are also depicted. During drilling, drilling mud flows upward through the lower portion  28  of the inner bore  26  and outward through the mud outlet  23 .  
         [0017]    The main housing  14  has an inner bore  26  within which the cartridge assembly  12  is removably seated. The inner bore  26  provides a lower portion  28  having a reduced diameter and an enlarged diameter portion  30  just above that. An upward and inward facing shoulder  32  is defined between those two portions. The inner bore  26  also includes three staged bore portions  34 ,  36  and  38  that present successive increases in diameter as the upper end of the main housing  14  is approached. Curved shoulders  40 ,  42  are defined at the intersections of these bore portions  34 ,  36  and  38 . Each shoulder  40 ,  42  is a segment of a sphere. The structure of these shoulders is better appreciated with reference to FIG. 3 which shows shoulder  42  in close up. As FIG. 1 shows, an annular channel  44  is cut into the upper end of the bore  26 . It is noted that the cartridge assembly  12  is removably seated in the main housing  14  and can be removed by pulling up on the cartridge assembly  12 .  
         [0018]    The cartridge assembly  12  is made up of an inner, generally cylindrical cartridge body  46  and an outer cartridge housing  48  that radially surrounds the cartridge body  46 . The cartridge body  46  is capable of rotation within the cartridge housing  48 . The cartridge body  46  is retained within the cartridge housing  48  by a retaining ring assembly  50 .  
         [0019]    The cartridge body  46  has an upper mandrel  51  that is made up of an upper section  52  and a lower section  54  that are affixed to one another by a threaded connection  56 . The lower section  54  is securely affixed to tubular body segment  58 . The upper mandrel  51  has a radially enlarged central portion  60  with reduced diameter portions  62 ,  64  located above and below, respectively.  
         [0020]    The cartridge body  46  defines a bore  66  that passes therethrough within which a drill string is disposed during drilling. The cartridge body  46  also retains an elastomeric gripping assembly  68  within the upper and lower sections  52 ,  54  of the upper mandrel  51 . The elastomeric gripping assembly  68  includes a selectively energizable elastomeric element  70  that can be hydraulically energized to protrude radially inwardly. Portions of a drill string (not shown) that are disposed within the bore  66  may be gripped by the element  70  in an energized state so that the cartridge body  46  will rotate with the drill string during drilling.  
         [0021]    The lower end of the tubular body segment  58  carries a conical elastomeric shroud  72  that has metal reinforcing members  74  within. The shroud  72  acts to grip portions of the drill string that pass through the tubular body segment  58 . The shroud  72  also functions to prevent mud flowing upwardly through the lower part  28  of the bore  26  from entering the bore  66 . It is noted that the radial inner surfaces of the cartridge housing  48  are shaped to accommodate the cartridge body  46  in a generally complimentary fashion.  
         [0022]    The retaining ring assembly  50  includes a cylindrically-shaped ring body  76  that has a number of radially-outwardly spring-biased pins  78  retained about its periphery. The pins  78  are shaped and sized to fit within the groove  44  in the upper end of the main housing  14 . Drawing handles  80  are used to selectively draw the pins  78  out of the groove  44  so that the ring body  76  can be removed from the upper end of the main housing  14  when necessary for maintenance or for replacement of parts.  
         [0023]    There are a plurality of upper roller bearings  82  and lower roller bearings  84  that are disposed between hardened shoulders  86  on both the cartridge body  46  and the surrounding cartridge housing  48 . The roller bearings  82 ,  84  maintain the cartridge body  46  a distance away from the cartridge housing  48  and roll on the hardened surface  86  to permit the cartridge body  46  to rotate with respect to the cartridge housing  48 .  
         [0024]    An annular dynamic seal assembly, shown generally at  90 , surrounds the tubular body segment  58  of the cartridge body  46 . The dynamic seal assembly  90  is stationarily mounted in housing  14  and seals against sleeve  58 , which rotates with the drill pipe. The dynamic seal assembly  90  has an outer body  92  that contains metal dynamic seals  94 ,  96  that radially surround the tubular body segment  58 . The dynamic seals  94 ,  96  are each annular members having a plurality of fluid apertures disposed radially therethrough. To properly act as seals, the dynamic seals  94 ,  96  require lubricant to constantly be pumped into the annular spaces  98  between the dynamic seals  94 ,  96  and the tubular body segment  58 . Thus, they function to provide active lubrication that permits the cartridge body  46  to easily rotate within the cartridge housing  48 .  
         [0025]    The body  92  of the seal assembly  90  is schematically shown in FIG. 2 apart from the remainder of the drilling head arrangement  10 . The body  92  has a substantially vertical and flat outer surface  100  along most of its length. There is, however, an upper, enlarged diameter portion  102 , the radial outward surface of which is curved to be substantially complimentary to the curved shoulder  42  of the main housing  14 . In addition, the body  92  defines a bore  103  along its entire length. The body  92  also contains five fluid passages  104 ,  106 ,  108 ,  110  and  112  that are depicted in phantom in FIG. 2. Each of the fluid passages  104 ,  106 ,  108 ,  110  and  112  has an inturned portion  114  at its lower end (see FIG. 2). The fluid passages  104 ,  106 ,  108 ,  110  and  112  each extend from the outer surface of the upper enlarged diameter portion  102  downwardly to a point along the bore  103  of the body  92 . With reference to FIG. 2, it can be seen that each of the fluid passages is of a different length so that each communicates with the internal bore  103  at a different elevation along the body  92  of the dynamic seal assembly  90 . It is also noted, with reference to FIG. 2, that the fluid passages  104 ,  106 ,  108 ,  110  and  112  are angularly spaced apart from one another about the circumference of the body  92 .  
         [0026]    Each of the fluid passages  104 ,  106 ,  108 ,  110  and  112  has, at its upper end, a static fluid seal  116 ,  118 ,  120 ,  122  and  124 , respectively. As FIG. 2 shows, each static seal is located at approximately an equivalent lateral location upon the radial exterior of the cartridge housing body  92 . Specifically, that lateral location coincides with the enlarged diameter portion  102  of the body  92 . The construction and operation of the static fluid seals are best understood with reference to FIG. 3 where exemplary static seal  116  is shown in greater detail. The static seal  116  is of the type described in U.S. Pat. No. 5,555,935 entitled “Fluid Connector for Well” issued to Brammer et al. and assigned to the assignee of the present invention. That patent is incorporated herein by reference. Basically, the static seal  116  includes an outer cylindrical retainer  130  that is secured within the body  92  by a threaded connection  132 . The retainer  130  radially surrounds a seal member  134  that defines a fluid pathway  136  to communicate fluid between the lower fluid port  18   b  and the fluid passage  104 . The seal member  134  is axially compressible and presents a mating face  138  that carries an elastomeric seal  140  thereupon. When the radial body  92  is disposed within the main housing  14 , the mating face  138  engages the shoulder  42  of the main housing  48  so that the fluid pathway  136  of the static seal  116  is aligned with the fluid port  18   b  in the main housing. The mating face  138  is urged against the shoulder  42  by the spring bias of the seal member  134 , thereby establishing a positive seal.  
         [0027]    The three lower fluid inlet ports  16   b  mate with static seals  116 , 118  and  120  and, via those, are connected with fluid passages  104 ,  106  and  108  respectively. The two lower fluid outlet ports  18   b  mate with static seals  122  and  124  and, via those, are connected with fluid passages  110  and  112 .  
         [0028]    The upper fluid passages  16   a ,  18   a  mate with static seals  142 ,  144  that are disposed within the upper end of the cartridge housing  48 . Fluid passages  146 ,  147  pass through the cartridge housing  48  between the static seals  142 ,  144  and the metal dynamic seal  148  that surrounds the reduced diameter portion  62  of the upper mandrel  51 . It is noted that a second dynamic seal  150  lies atop the dynamic seal  148 . Dynamic seals  148 ,  150  are stationary with housing  14  and slidingly engage cartridge mandrel  51 , which rotates with the drill pipe. It will be understood by those of skill in the art that there are also fluid passages and static seals interconnected with the dynamic seal  150  as well as fluid inlet and outlet ports. Because these static seals and passages lie outside of the plane of the drawing in FIGS. 1A and 1B, they are not illustrated there. Nonetheless, these components have substantially the same structure as the static seals  142 ,  144  and passages  146 ,  147  shown for dynamic seal  148 . The dynamic seals  148 ,  150  are similar in construction and operation to the dynamic seals  94 ,  96  described earlier and are physically axially offset in location from the dynamic seals  94 ,  96 .  
         [0029]    In operation, a lubricating fluid, typically a hydraulic fluid, is pumped via hydraulic conduits (not shown) into the fluid inlet ports  16   a ,  16   b  during a drilling operation in which a drilling string passes through cartridge assembly  12 . The hydraulic fluid is used to lubricate the dynamic seals  94 ,  96  and  148 ,  150  as the body  46  and sleeve  58  rotate within the cartridge housing  48 . The hydraulic fluid pumped into the upper fluid inlet ports  16   a  is transmitted to dynamic seals  148 ,  150  via fluid inlet port  16   a , static seal  142  and fluid passage  146 . The hydraulic fluid lubricates each of these bearings for proper operation. Hydraulic fluid circulates from the rotating drilling head assembly  10  by passing through the fluid passage  147  and static seal  144  to outlet port  18   a . Hydraulic fluid that is pumped into the lower fluid inlet port  16   b  is transmitted to dynamic seals  94 ,  96  via static seals  116 ,  118  and  120  and fluid passages  104 ,  106  and  108 . The dynamic seals  94 ,  96  are lubricated, and spent fluid is returned via the fluid passages  110 ,  112  and static seals  122  and  124  to fluid outlet ports  18   b.    
         [0030]    The employment of a plurality of static seals that are angularly spaced about the circumference of the drilling head assembly  10  allows fluid to be passed inwardly toward the radial center of the drilling head assembly  10  at several different heights. However, only one or two changes in the external diameter for the cartridge housing  48  are required. These changes in diameter occur at the curved shoulders  40  and  42 . At the same time, numerous fluid inlet ports and outlet ports may be accommodated. As FIG. 2 illustrates, five static seals are available on the radial body  92  for mating with inlet and outlet ports  16   b ,  18   b . In addition, static seals are very resilient, and the cartridge  12  may be replaced numerous times without the fluid seals failing.  
         [0031]    While the invention has been described with reference to a preferred embodiment, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various modifications and changes without departing from the scope of the invention.