Patent Publication Number: US-7909105-B2

Title: Independent wellhead drilling adapter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the filing date of U.S. provisional application Ser. No. 60/948,306, filed on Jul. 6, 2007, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to oil and gas well drilling, and, in particular to an adapter for connecting a blowout preventer to an independent wellhead. 
     BACKGROUND 
     Conventional adaptors for coupling devices such as, for example, a blow out preventer (“BOP”) to a wellhead typically require a threaded connection. As a result, such adaptors require rotation of the BOP relative to the wellhead during installation. This connection requiring rotation is time consuming and requires a large well bay to allow the BOP to rotate and connect to such a threaded connector. Since many new oil rigs have small well bays this create logistical problems. Other conventional adaptors for coupling devices to a wellhead require that the wellhead threads must be non-standard thereby adding cost and complexity. The present exemplary embodiments are directed to overcoming some of the limitations of conventional adaptors used to couple devices to wellheads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating an adapter connecting a blowout preventer to an independent wellhead, in an exemplary embodiment of the present technique. 
         FIG. 2  is a view of the wellhead of  FIG. 1 , shown with the adapter and the blowout preventer removed and casing installed, in an exemplary embodiment of the present technique. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings and description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings. 
     Referring to  FIG. 1 , a first casing  11  extends into the well for a first distance and has an upper end landing ring illustrated in  FIG. 1 . A second casing  13  extends into the well to a second depth and has an upper end with a landing ring  15  that lands on the upper end of first casing landing ring  11 . The upper end of casing  13  is threaded and in this example is connected to a casing collar  17 . Casing collar  17  has internal threads on its upper end. 
     A wellhead  19  has a lower set of external threads  21  that secure to the internal threads in casing collar  17 . Wellhead  19  is preferably a type referred to as an “independent wellhead”, which has specifications dictated by the American Petroleum Institute. Currently, the specifications are governed by API Specification 11IW, June, 2000 “Specification for Independent Wellhead Equipment”. Wellhead  19  may be a casing head or it may be a tubing head. Lower threads  21  may be external or internal and still fall within the specification. Wellhead  19  has one or more outlets  23 , extending through its sidewall. Outlet  23  is shown connected to a nipple  27  for connection to additional equipment. Outlet  25  is shown connected to a valve  29 . Wellhead  19  has an interior bowl or profile  31  extending above outlets  23 ,  25 . In this embodiment, profile  31  is a conical taper, however other configurations for profile  31  are allowed within the API specification. Wellhead  19  has an upper thread set  33  on its exterior extending downward from its rim. Upper thread set  33  is also governed by the API specification and comprises specified API pipe threads. 
     In this embodiment, a drilling adapter  35  mounts to wellhead  19  during drilling. Adapter  35  lands on the rim or upper end of wellhead  19 . A seal  37  on the lower side of adapter  35  seals against the upper end of wellhead  19 . Adapter  35  has a connector ring  39  that is secured to it for connecting adapter  35  to wellhead  19 . In this example, connector ring  39  is secured by threads  41  to a threaded portion on the exterior of adapter  35 . Lock pins  43  extend through the sidewall of connector ring  39  into engagement with vertical grooves formed below threads  41  to prevent lock ring  39  from rotating relative to adapter  35 . Connector ring  39  could be connected to adapter  35  in manners other than by threads, if desired. 
     Connector ring  39  has a lower portion  40  that extends below adapter  35 . Lower portion  40  extends inward under the lower end of adapter  35  and surrounds wellhead threads  33 . Lower portion  40  has an internal annular recess  45  that has an open side facing wellhead threads  33 . A plurality of segments  47  are carried in annular recess  45 . Each segment  47  is arcuate section of a ring and has a portion of a thread set  49  on its inner face. Thread set  49  is formed to match threads  33  of wellhead  19 . Each segment  47  is movable radially from the outer position shown on the left side of  FIG. 1  to the inner position shown on the right side. In the inner position, segment threads  49  will be in engagement with wellhead threads  33 . In an exemplary embodiment, the profile of the threads of the segments  47  are configured relative to the threads on the wellhead  19  such that, as the threads of the segments  47  are tightened against the threads on the wellhead  19 , the connector ring  39  is pulled down, the seal  37  engages and thereby seals against the top of the wellhead. When in the inner position, the sides of segments  47  abut each other and the thread sets  49  define a continuous set of threads that mate with wellhead threads  33 . Segments  47  may be manufactured by first cutting a set of threads on the inner diameter of a ring, then cutting the ring into individual segments. In the outer position, segment threads  49  will be spaced radially outward from wellhead threads  33 . 
     The mechanism to move each segment  47  radially inward and outward in this embodiment comprises a screw  51  that extends through a threaded hole in connector ring  39  radially outward from recess  45 . Each screw  51  has an inner end  53  that engages a recess within one of the segments  47  and is rotatable relative to the segment  47 . Preferably each screw  51  has a polygonal outer end for receiving a wrench to rotate screw  51 . 
     Adapter  35  also has a bore  55  that aligns with the upper end of wellhead profile  31 . Prior to drilling through wellhead  19 , the operator installs a drilling or wear bushing  57 , shown by dotted lines. Wear bushing  57  slides down over profile  31  to protect profile  31  from damage during drilling. Wear bushing  57  has an upper end that is releasably retained with adapter  35 . In this example, the retainer comprises a plurality of radially extending screws  59  extending through adapter  35 . Each screw  59  has a pointed end that engages an annular recess on the exterior of wear bushing  57 . Screws  59  extend radially through threaded holes in adapter  35 . 
     A blowout preventer  61  mounts on top of adapter  35 . Blowout preventer  61  may be a variety of types and is shown by dotted lines. In this example, blowout preventer  61  secures to a flange portion of adapter  35  by means of bolts  63 . 
     In operation, the operator will initially drill the well and install casings  11  and/or  13 . The operator then installs wellhead  19  on casing  13  at the rig floor and run in the wellhead  19 , collar  17 , and landing ring  15  as illustrated in  FIG. 1 . The operator places adapter  35  on wellhead  19  and rotates screws  51  to cause segments  47  to move into mating engagement with wellhead threads  33 . There is no need to rotate adapter  35  relative to wellhead  19 . The operator inserts well bushing  57  and rotates screws  59  inward to secure wear bushing  57 . Adapter  35  may have previously connected to blowout preventer  61  prior to landing adapter  35  on wellhead  19 . The operator drills through wellhead  19  to the total depth. 
     The operator removes wear bushing  57  and in this example, installs a string of casing  65 , shown in  FIG. 2 . Casing  65  may be run through BOP  61  ( FIG. 1 ). Casing  65  is cemented in place and a hanger mechanism  67  supports casing  65 . In this example, hanger  67  comprises tapered slips that engage profile  31  in wellhead  19 . BOP  61 , adapter  35  and connector ring  39  ( FIG. 1 ) are removed as a unit and reused for drilling another well. The operator installs a packoff  69  between an upper portion of wellhead profile  31  and casing  65 . A top connector  71  has an inner portion that fits over packoff  69  to retain packoff  69  and to deform it into sealing engagement with wellhead profile  31 . Top connector  71  has a lower portion with internal threads  73  that engage upper threads  33  on wellhead  19 . 
     Other types of completions after drilling are available, but these completions would also utilize wellhead upper threads  33 . Furthermore, as mentioned, rather than supporting casing, wellhead  19  could support a string of tubing. 
     The present exemplary embodiments provide an assembly for connecting a component to a wellhead comprising external threads on an end portion thereof in which the assembly may be connected to the threaded portion of the wellhead without having to rotate the component. 
     It is understood that variations may be made in the above without departing from the scope of the invention. While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.