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BACKGROUND 
     The invention relates generally to a system and method of securing a wellhead connector to casing of a wellhead assembly that has been damaged by a storm or other similarly destructive event. In particular, the invention relates to a system and method of installing a wellhead connector to the casing of a well having casing and production tubing, which extends from the sea floor to a surface wellhead. 
     Surface wellheads are a common feature of oil production. A production tree is attached to the wellhead to control the flow of oil and/or gas produced by the well. The oil and/or gas from the well passes through production tubing to a production tree. The production tree, in turn, may be coupled to a platform that couples the oil and gas to a pipeline for transfer to a processing facility. 
     A violent storm, such as a hurricane, can damage wells located on land, as well as offshore. For example, a storm can damage an offshore platform, the production tubing, and/or the production tree of a well by pulling the production tubing from its platform. Furthermore, tidal forces from a storm can blow over a production tree, damaging both the production tree and the production tubing. 
     Previous efforts at securing wells damaged by storms have been time-consuming and ineffective. These efforts have included installing devices using numerous loose bolts. However, installing these loose bolts is time-consuming and the bolts may be lost or misplaced, adding to the installation time. This is even more problematic for subsea well heads. 
     Therefore, a more efficient technique is desired for securing a well damaged by a storm or any other catastrophic event. In particular, a technique is desired that would enable a well to be secured quickly and securely. 
     BRIEF DESCRIPTION 
     A technique is provided for securing a well damaged by a storm or similar catastrophic event. The techniques utilizes a casing head assembly that may secured to the casing of the damaged well by tightening a plurality of set screws to drive slips into the casing. Before installing the casing head assembly, the casing of the damaged well is prepared for receiving the casing head assembly. For example, any valves secured to the well may be removed and the casing and production tubing of the well may be cut so that the production tubing extends a relatively-short defined distance from the end of the casing. Some preparation of the casing head assembly may also be performed, such as cleaning and coating surfaces. 
     Once the casing, production tubing, and the casing head assembly are ready, a portion of the casing head assembly, a casing head, may be installed onto the casing. As the casing head is lowered into position on the casing, the control line of the downhole safety valve of the well is fed into an inner bore of the casing head and then out of the casing head via a control line port through the side of the casing head. Once the casing head is in position on the casing, the casing head set screws may be tightened to secure the casing head to the casing. 
     The casing head assembly may also comprise a tubing hanger. The tubing hanger may be installed in the casing head after the casing head is secured to the casing. Tubing head set screws may then be tightened to activate the tubing hanger to secure the production tubing to the casing head. 
     In addition, the casing head assembly may also comprise a latch-lock connector that may be secured to the casing head. The latch-lock connector may be stabbed into the casing head and rotated approximately one-quarter turn. This locks the latch-lock connector to the casing head. A corrosion cap may then be secured to the latch-lock connector to cover the production tubing. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is an elevation view of a casing head assembly secured by set screws to the casing of a damaged production assembly, in accordance with an exemplary embodiment of the present technique; 
         FIG. 2  is a cross-sectional view of the casing head assembly taken along the longitudinal axis of the casing head assembly of  FIG. 1 , in accordance with an exemplary embodiment of the present technique; 
         FIG. 3  is a block diagram of a method for securing a wellhead using a casing head assembly that is securable to casing using set screws, in accordance with an exemplary embodiment of the present technique; 
         FIG. 4  is a cross-sectional view of the casing head secured to casing using set screws, in accordance with an exemplary embodiment of the present technique; 
         FIG. 5  is a cross-sectional view of a tubing hanger secured to the casing head using set screws, in accordance with an exemplary embodiment of the present technique; 
         FIG. 6  is a cross-sectional view of a latch-lock connector and corrosion cap secured to the casing head, in accordance with an exemplary embodiment of the present technique; and 
         FIG. 7  is a cross-sectional view of a casing head adapted to receive a control line from the well at an angle of forty-five degrees, in accordance with an alternative exemplary embodiment of the present technique. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , the present invention will be described as it might be applied in conjunction with an exemplary technique, in this case a casing head assembly for securing a damaged wellhead, as represented generally by reference numeral  20 . The casing head assembly  20  is adapted to attach to the end of a string of casing  22  extending from a well bore. In a normal well in production, a production valve assembly would extend above a well head secured to the casing  22 . In addition, production tubing would extend from the well within the casing and through the production valves to transport oil and/or gas to a surface platform, subsea manifold, or other location. In this embodiment, the casing head assembly  20  has been adapted to secure the innermost of several casing strings, as well as production tubing extending from the well to prevent any fluids therein from leaking into the surrounding waters. However, the casing head assembly  20  may be adapted to secure additional casing strings other than the innermost casing string of a well. For this, additional casing heads with larger diameters may be attached to the casing head assembly. 
     In the illustrated embodiment, the casing head assembly  20  comprises a casing head  24 , a latch-lock connector  26 , a corrosion cap  28 , and a vent valve  30 . The casing head  24  is adapted to attach to the casing  22  and secure the production tubing extending from the casing  22 . The latch-lock connector  26  is adapted to connect to the casing head  24  to enable the corrosion cap  28  to be secured to the casing head  24 . One end of the latch-lock connector  26  is adapted to secure to the casing head by being stabbed into the casing head  24  and then being turned one-quarter of a turn. The opposite end of the latch-lock connector  26  is adapted to receive and secure the corrosion cap  28 . The corrosion cap  28  has one end that is adapted to be secured by the latch-lock connector  26 . The opposite end of the corrosion cap  28  is configured with the vent valve  30  to enable any gasses that leak into the corrosion cap  28  to be vented. For example, the vent valve  30  may prevent an explosive concentration of gases from building up within the corrosion cap  28 . 
     The casing head  24  has a series of casing head set screws, or dogs  32 , spaced circumferentially around the lower end of the casing head  24 . As will be discussed in more detail below, within the casing head  24  are slips that bite into the casing  22  when the casing head set screws  32  are tightened. These slips grip the casing  22  and secure the casing head  24  to the casing  22 . In this embodiment, the casing head  24  has six casing head set screws  32 . A family of casing heads may be established to correspond to various standard casing sizes. In addition, the outer diameters of the casing heads  24  are established to correspond to a larger standard casing size. Thus, if addition to the inner casing string, a larger casing string is desired to be secured, a smaller casing head may be inserted into a larger casing head in a wedding cake arrangement. 
     The casing head  24  also has a control line tie-in  34  that enables external access to a control line extending from the well within the casing  22 . The control line tie-in and control line enable pressure to be applied to the well to set a downhole safety valve. The control line is fed to the control line tie-in  34  through a port through the casing head  24 . The port is angled at an acute angle relative to an axial inner bore within the casing head to make it easier for the control line to be fed through the casing head  24 . In addition, the illustrated embodiment of the casing head has a valve to enable fluid to be removed from within the casing through an annulus formed between the casing and the production tubing. 
     The casing head  24  also has a series of tubing hanger set screws, or dogs  38 , that are spaced circumferentially around an upper portion of the casing head  24 . The tubing hanger set screws  38  are oriented to activate a tubing hanger within the casing head  24 . As will be discussed in more detail below, the tubing hanger is positioned so that the production tubing extends through the tubing hanger within the casing head When activated, the tubing hanger expands outward to engage the casing head  24  and inward to engage the production tubing. This secures the production tubing to the casing head  24 . In the illustrated embodiment, the casing head  24  has six tubing hanger set screws  38 . 
     Referring generally to  FIG. 2 , a cross-sectional view of the casing head assembly  20  is presented. In addition, the production tubing  40  and control line  42  may be seen in this view. The casing  22  and production tubing  40  are cut in a wedding cake arrangement with the production tubing  40  extending a desired distance above the casing  22 . 
     As noted above, slips  44  are used to secure the casing head  24  to the casing  22 . As the casing head set screws  32  are tightened into the casing head  24 , the casing head set screws  32  drive the slips  44  downward. This downward motion causes the slips  44  to bite into the casing  22 , thereby gripping the casing  22  and securing the casing head  24  to the casing  22 . 
     The casing head assembly  20  also utilizes a pack-off seal  46  that forms a seal between the casing head  24  and the casing  22 . In this embodiment, the casing  22  is cut and prepared to facilitate the formation of a seal with the pack-off seal  46 . The casing head  24  is adapted to receive the pack-off seal  46  and hold it in position so that the seal is made when the casing head  24  is lowered onto the casing  22 . The casing head  24  also has a test port  47 . Hydraulic pressure may be applied to casing head  24  through the test port  47  to verify that the casing head  24  is securely attached to the casing  22 . 
     The casing head  24  has a valve port  48  that extends from an inner bore  50  of the casing head  24  to the exterior. In this embodiment, the valve port  48  is threaded to enable an annulus valve  36  to connect to the casing head  24 . The valve port  48  enables the casing  22  to be drained through the casing head  24 . The annulus valve  36  enables the drainage of the casing  22  to be controlled. 
     The casing head  24  also has a control line port  52  that extends through a side of the casing head  24  to the inner bore  50  of the casing head. The control line port  52  is oriented at an acute angle relative to a central axis  54  of the casing head assembly  20 . For example, the control line port  52  may be angled at an angle of forty-five degrees or sixty degrees relative to the central axis  54 . Insertion of the control line  42  through the control line port  52  is eased markedly by having the control line port  52  oriented at an acute angle, rather than a ninety degree angle. In the illustrated embodiment, the control line port  52  is oriented at an angle of sixty degrees. 
     A tubing hanger  56  is used to secure the production tubing  40  to the casing head  24 . The tubing hanger  56  has two semi-circular half-pieces that are secured to each other by screws. The two half-pieces of the tubing hanger  56  may be separated to facilitate placing the tubing hanger  56  around the production tubing  40 . Once located around the production tubing  40 , the two pieces of the tubing hanger  56  may be joined. In addition, each of the two tubing hanger pieces has an upper portion  58  and a lower portion  60  held together by screws  62 . The tubing hanger  56  also has a rubber packer  64 . 
     The tubing hanger  56  sits in a landing in the casing head  24 . The top of the upper portion  58  of the tubing hanger has a beveled surface. When the tubing hanger set screws  38  are tightened they drive against the beveled surface of the tubing hanger  56 , which drives the upper portion  58  of the tubing hanger  56  downward toward the lower portion  60 . This causes the rubber packing  64  to be expanded outward toward the casing head  24  and inward toward the production tubing  40 . This secures the production tubing  40  to the casing head  24 . 
     In the illustrated embodiment, the casing head  24  has a female threaded connector  66  and the latch-lock connector  26  has a corresponding male threaded connector  68 . The female threaded connector  66  and the male threaded connector  68  form a high-strength connection. The connectors  66 ,  68  are adapted to be stabbed together and then rotated approximately one-quarter turn to make-up the connection. In this embodiment, a quadruple helix thread form is used by the connectors  66 ,  68 . The threads interlock as they are rotated relative to each other. 
     In the illustrated embodiment, the vent valve  30  is located at the highest point of the corrosion cap  28  to prevent as little build-up of gas as possible within the corrosion cap  28 . The vent valve  30  may utilize a check valve or some other type of pressure-relieving valve. 
     Referring generally to  FIG. 3 , a method of securing a damaged well using the casing head assembly  20  is presented, and represented generally by reference numeral  70 . Initially, the casing  22  is prepared for receiving the casing head assembly, represented generally by block  72 . If the well has a “Christmas tree” or similar production valves, these must be cut from the end of the casing. Preferably, the end of the casing  22  is cut to provide a desirable surface for forming a seal. In addition, the outer diameter of the end of the casing  22  should be beveled. In addition, it is preferable that the casing is cut so that a straight portion of casing is presented to the casing head assembly  20 . As noted above, the production tubing  40  and casing  22  are cut in a wedding cake arrangement with the production tubing  40  cut to extend a defined distance from the end of the casing  22 . In addition, if there is more than one string of casing in the well, the inner casing is cut so that it extends from the other strings of casing to provide an adequate surface to receive the casing head  24 . In addition, if it is desired to secure the ends of other strings of casing, they should also be cut in this wedding cake arrangement to enable these strings of casing to receive additional casing head sections. 
     Some preparation of the casing head assembly  20  may also be performed, as represented generally by block  74 . For example, the casing head assembly  20  may be cleaned and a coat of light grease may be applied to all moving parts. Various dimension checks may also be preformed. 
     Once the casing  22 , production tubing  40 , and casing head assembly  20  are ready, the casing head  24  may be installed onto the casing  22 , as represented generally by block  76 . A lifting device may be used to lower the casing head  24  to the casing  22 . The control line  42  is fed into the inner bore  50  of the casing head  24  and though the control line port  52  as the casing head  24  is lowered into position. Once the casing head  24  is in position on the casing, the casing head set screws  32  may be tightened. Preferably, the casing head set screws  32  are tightened in an alternating crisscross manner in increments until a desired torque is reached. In addition, the casing head  24  may be pulled to ensure that the casing head  24  is secured to the casing  22 . For example, a 10,000 lbf pull may be applied to the casing head  24  to ensure that the casing head  24  is properly gripping the casing  22 . The casing head set screws  32  may be re-tightened to the desired torque after the test pull. 
     In this embodiment of the method, the tubing hanger  56  is installed in the casing head  24  after the casing head  24  is secured to the casing  22 , as represented generally by block  78 . Initially, the two halves of the tubing hanger  56  are separated. The two half-pieces are then wrapped around the production tubing  40  and secured together with screws. The tubing hanger  56  is then lowered into the casing head toward a landing shoulder within the casing head  24 . Preferably, the annulus valve  36  is open during this process. The tubing head set screws  38  are then tightened in an alternating crisscross manner in increments until a desired torque is reached. 
     In the illustrated embodiment, the latch-lock connector  26  is secured to the casing head  24  after the tubing hanger  56  is activated within the casing head  24 , as represented generally by block  80 . The latch-lock connector  26  is stabbed into the casing head  24  and rotated approximately one-quarter turn. This brings all of the threads of the connectors  66 ,  68  into engagement. 
     The corrosion cap  28  is then secured to the latch-lock connector  26  over the production tubing  40 , as represented generally by block  82 . The production tubing  40  is thereby covered so that any leakage from inside the production tubing is contained within the corrosion cap  28 . If the vent valve  30  is separate from the corrosion cap  28  it would now be installed. Thus, the casing  22  and production tubing  40  are secured and prevented from leaking into the surrounding waters. In addition, access to the control line  42  of the well is provided. 
     Referring generally to  FIG. 4 , the process of installing the casing head  24  to the casing  22  is presented. The casing head  24  is lowered into position on the casing  22 , as represented by arrow  84 . The pack-off seal  46  is seated on the end of the casing  22 , forming a seal between the casing head  24  and the casing  22 . Once in position, the casing head set screws  32  are tightened, as represented by arrows  86 . Tightening the casing head set screws  32  causes the casing head set screws  32  to drive the slips  44  downward, biting into the casing  22 . This biting action of the slips  44  grips the casing  22  to the casing head  24 , securing the casing head  24  to the casing  22 . 
     Referring generally to  FIG. 5 , the process of installing the tubing hanger  56  within the casing head  24  is presented. As discussed above, in this embodiment, the tubing hanger  56  is composed of two half-pieces that are joined together around the production tubing  40 . The tubing hanger set screws  38  are then tightened, as represented by arrow  88 . This causes the upper portion  58  of the tubing hanger  56  to be driven downward toward the lower portion  60  of the tubing hanger  56 . 
     Referring generally to  FIG. 6 , the process of securing the latch-lock connector  26  and the corrosion cap  28  to the casing head  24  is presented. The latch-lock connector  26  is stabbed into the casing head  24 , as represented generally by arrow  90 . The latch-lock connector  26  is then rotated clockwise approximately one-quarter turn, or ninety degrees, to secure the latch-lock connector  26  and the corrosion cap  28  to the casing head  24 , as represented by arrow  92 . 
     Referring generally to  FIG. 7 , an alternative embodiment of a casing head assembly is presented, and represented generally by reference numeral  94 . In this embodiment, the casing head  96  has a control line port  98  that is angled at an angle of forty-five degrees relative to the central axis  54  of the casing head  24 , rather than sixty degrees as in the previous embodiment. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Summary:
A technique for securing a subsea well that has had some of its components damaged as a result of a storm or other catastrophic event. The techniques utilizes a casing head assembly that may secured to the casing of the damaged well by tightening a plurality of set screws to drive slips into the casing. The casing head assembly may also comprise a tubing hanger. Tubing head set screws may then be tightened to activate the tubing hanger to secure the production tubing to the casing head. The casing head assembly may also comprise a latch-lock connector that may be secured to the casing head by stabbing the latch-lock connector into the casing head and rotating the connector approximately one-quarter turn. A corrosion cap may then be secured to the latch-lock connector to cover the end of the production tubing.