Abstract:
A method of providing a communication conduit for a down-hole tool includes the steps of: forming a communication port at an existing portion of the down-hole tool located below the valves of the Christmas tree; and extending the communication conduit through the formed port.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the national stage of International Application No. PCT/GB2009/051492, which was filed on Nov. 6, 2009, which claims the benefit of United Kingdom Patent Application Serial No. 0820407.5, which was filed on Nov. 7, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a method and apparatus for providing communication at surface for down-hole tools. 
       BACKGROUND OF THE INVENTION 
       [0003]    Generally wells undergo what is termed a work-over to install various items of new equipment. This can involve removing existing equipment, the cost of which may make the work-over uneconomic. To overcome the cost of the work-over, it is possible to install smaller diameter completion components inside the existing completion tubing string. As this work may be carried out at a lower cost than removing the existing equipment and tubing string, the economic case will be better. 
         [0004]    It is relatively easy to install this retrofit completion using standard techniques and practices. The purpose of installing this insert completion is to produce more oil and gas than was achieved with the existing equipment, either over a longer period to extend the field life or to produce oil or gas at higher rates. 
         [0005]    The designs of some insert completions, such as artificial lift, require a new communication path from the surface to the internal components. This path can be for example but not limited to: fluid for jet pumps, saponification or injection of scale and corrosion inhibitors; electric cables for downhole pumps and monitoring; gas for insert gas lift; or fiber optic for monitoring and control purposes. Therefore, the term “communication path” should accordingly be interpreted in broad terms. 
         [0006]    Providing this path involves modifying the wellhead equipment in some manner. However, the cost of modifying the wellhead equipment can be high, again limiting the economic case for installing this equipment. Typical methods of modifying the wellhead can include fitting a spool piece above or below the valve block or Christmas tree ( FIGS. 1 and 2 ). This spool piece is used to provide the communication required from surface to the retrofit completion. However, by positioning a spool piece either above or below a tree, further problems are created. 
         [0007]    If the spool piece is installed above the tree, a communication line has to extend through the valve block, effectively isolating the surface safety valves. Most safety regimes would not allow such a practice in the long term for semi-permanent installations. For temporary installations, Blow Out Preventers (BOPs) could be included above the spool, but this again detrimentally affects the wellhead and flow lines. 
         [0008]    If the spool is installed below the Christmas tree, the tree has to be removed, a spool fitted and the tree replaced. This positions the surface safety valves above any communication line, giving well control. However the flow lines, which connect the tree to downstream processing and storage facilities require to be modified. Again the expense and time required to obtain new, or to modify existing, flow lines can render the project uneconomic. 
         [0009]    Various methods and apparatus have been described which attempted to circumvent the expense in installing these retrofit completions. One such system is described in UK patent application GB2426771, Retrofit remedial subsurface safety valve (SSSV). Fundamentally this system positions the spool piece above the tree and provides a function to mimic the operation of the existing valves in the tree, which are redundant by virtue of the installation of this equipment. 
         [0010]    It is desirable to provide a method and apparatus for making a communication path at the wellhead to the retrofit or insert completion without the need for spool pieces, removing the tree or modifying flow lines. 
       SUMMARY OF THE INVENTION 
       [0011]    In standard wellheads, just below the Christmas tree, there is a tubing hanger and tubing hanger bowl. Within the tubing hanger is a landing nipple or threaded locater feature that allows for the installation of a tubing hanger plug. The tubing hanger plug is installed to isolate the well so that the tree can be removed or modification work carried out in safety. The well tubing string is suspended from the hanger in the bowl and locked down with a bolting system. This bolting system extends to the exterior of the wellhead to allow the tubing string to be removed. 
         [0012]    The invention may utilize the tubing hanger plug (THP) landing profile and the bolting system if required to provide the communication path. There is redundancy within this bolting system, so the invention may remove one or more of the bolts and replaces it with a feed-through device, which connects to a device located in the THP landing nipple or in some other suitable location below the tree. 
         [0013]    Alternatively a new hole may be created to provide the access from the exterior to the well tubing string at the hanger, for example by hot-tapping which is an existing technique for creating new holes in pressurized equipment. 
         [0014]    The design of the THP landing profile is such that the seal bore does not extend a sufficient distance above the locking groove to land seals to effect a seal tight communication between the feed-through and the internal insert hanger. It is desirable to allow installation of an insert completion hanger and communication sub that does not require annular seals on the hanger. 
         [0015]    According to the first aspect of the present invention there is provided a method of providing a communication conduit for a down-hole tool, the method comprising the steps of: 
         [0016]    forming a communication port at an existing portion of the down-hole tool located below the valves of the Christmas tree; and 
         [0017]    extending the communication conduit through the formed port. 
         [0018]    The method may include forming the communication port at the tubing hanger. The method may include forming the communication port at the bolt hole of the tubing hanger, and the step of forming the communication port may comprise removing an existing bolt of the tubing hanger. The method may include installing a replacement fitting for the removed bolt. 
         [0019]    The method may include forming a new aperture at the tubing hanger to form the communication port may comprise removing an existing bolt of the tubing hanger. The method may include installing a replacement fitting for the removed bolt. 
         [0020]    The method may include forming a new aperture at the tubing hanger to form the communication port. The new aperture may be formed using hot-tapping. The method may include the step of testing to ensure non-interference with an existing penetration. 
         [0021]    The method may include providing a conduit hanger within the down-hole tool. The conduit hanger may be mounted at an internal profile of the down-hole tool. The conduit hanger may be mounted at an internal profile of the down-hole tool. The conduit hanger may be mounted at an internal profile of the tubing hanger. The conduit hanger may be mounted at the tubing hanger plug profile of the tubing hanger. The method may include locking the conduit hanger in position using one or more keys. 
         [0022]    The conduit hanger may include a profile for receiving a tubing hanger plug. 
         [0023]    The method may include installing a communication sub within the down-hole tool. The communication sub may be installed above the conduit hanger. The method may include aligning the communication sub to the communication port. 
         [0024]    The method may include sealing the communication port. The replacement fitting may include sealing means, such as a sleeve. 
         [0025]    The method may include injecting fluid to the communication conduit. The method may include preventing injected fluid from exiting via the communication port. The method may include providing one or more flow ports at the communication sub to allow fluid to pass through the communication sub. 
         [0026]    According to a second aspect of the present invention there is provided a communication apparatus for a down-hole tool, the apparatus comprising: 
         [0027]    a communication port formed at an existing portion of the down-hole tool located below the valves of the Christmas tree; and 
         [0028]    a communication conduit extending through the communication port. 
         [0029]    The communication port may be formed at the tubing hanger. The communication port may be formed at a bolt hole of the tubing hanger. The apparatus may include a replacement fitting for the removed bolt. 
         [0030]    The apparatus may include a conduit hanger provided within the down-hole tool. The conduit hanger may be adapted to be mounted at an internal profile of the down-hole tool. The conduit hanger may be adapted to be mounted at an internal profile of the tubing hanger. The conduit hanger may be adapted to be mounted at the tubing hanger plug profile of the tubing hanger. The apparatus may include one or more keys for locking the conduit hanger in position. 
         [0031]    The conduit hanger may include a profile for receiving a tubing hanger plug. 
         [0032]    The apparatus may include a communication sub locatable within the down-hole tool. The communication sub may be installable above the conduit hanger. The replacement fitting may comprise alignment means, such as a pin, for aligning the communication sub to the communication port. The communication sub may include alignment means, such as a slot, for aligning the communication sub to the communication port. 
         [0033]    The replacement fitting may include sealing means, such as a sleeve, for sealing the communication port. 
         [0034]    The communication sub may include one or more sub ports to allow the injection of fluid to the communication conduit. A check valve may be provided at one or more of the sub ports to prevent injected fluid from exiting via the communication port. The communication sub may include one or more flow ports to allow fluid to pass through the communication sub. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    A particular embodiment of the invention as utilized in a hydraulic line system will now be described by way of example only with reference to the accompanying drawings in which: 
           [0036]      FIG. 1  shows a solution for providing the communication path with a spool piece mounted above the Christmas tree, to demonstrate the current state of the art. 
           [0037]      FIG. 2  shows a solution for providing the communication path with a spool piece mounted below the Christmas tree to demonstrate the current state of the art. 
           [0038]      FIG. 3  shows a general view of the invention, with the position of the communication port at the tubing hanger. 
           [0039]      FIG. 4  shows a typical wellhead configuration with hold down bolts restraining a tubing hanger. 
           [0040]      FIG. 5  shows the same wellhead configuration with the new access port. 
           [0041]      FIG. 6  shows a detailed view of the conduit hanger in the THP landing nipple. 
           [0042]      FIG. 7  shows a detail of the orientation pin, part of the feedthrough system, used to orientate the communication sub. 
           [0043]      FIG. 8  shows the detail of the communication sub landed on top of the conduit hanger, orientated by the pin as shown in  FIG. 7 . 
           [0044]      FIG. 9  shows the feedthrough activated, providing communication from the exterior of the wellhead to the insert completion. 
           [0045]      FIG. 10  shows a cross-section of the communication sub with the feedthrough activated, showing the option of multiple ports within the communication sub. 
           [0046]      FIG. 11  shows the entire system installed within a typical tubing hanger system 
       
    
    
     DETAILED DESCRIPTION 
       [0047]      FIG. 1  shows a schematic representation of a prior art wellhead valve block or Christmas tree  1 , with a flowline  4  for production of oil and gas. Valves  5  are used to control the flow of oil and gas. A spool piece  2 A is positioned above the tree  1 , with a conduit  6  running through the valves, effectively rendering them redundant. The tree  1  is mounted on a tubing hanger  7 , which has a profile  10  for positioning tubing hanger plugs or other items of equipment. 
         [0048]    In  FIG. 2 , the prior art spool piece  2 B is positioned below the tree  1 , hence the existing flowline  4  no longer mates to the outlet from the tree  1 . Valves  5  are free to operate. Communication port  3  mates to a conduit hanger  8 , locked into the spool piece  2 B with keys  9 .  FIGS. 1 and 2  expose the limitations to the current state of the art from both safety and economic aspects. 
         [0049]      FIG. 3  shows an alternative schematic according to the invention for connecting the conduit  6  of the insert completion via a new penetration  11  within the tubing hanger bowl, either through an existing threaded hole for the tie down bolts for the tubing hanger or an entirely new hole. In this instance the valves  5  are free to operate and the flowline  4  is aligned to the outlet of the tree  1 . 
         [0050]      FIG. 4  shows the tubing hanger  7  held down by bolts  14 . Preferably, one of these bolts  14  is removed to perform the hot tapping operation to form the new port  11  as shown in  FIG. 5 . Existing penetrations  16  through the hanger  7  are commonplace, for installing hydraulic lines for operating down hole safety valves and for installing electrical lines for pressure and temperature gauges. Technology exists from the companies that perform the hot-tapping operation to test the chosen tie-down bolt  14  before drilling the hole. This ensures that the new port  11  does not intersect with an existing penetration through the tubing hanger  7 . Alternatively, the hot tap operation could be made through the entire wellhead and tubing hanger  7 , if the option to remove a tie down bolt was not available. 
         [0051]      FIG. 6  shows that the conduit hanger  8  is locked into the tubing hanger profile  10  with keys  9 . The conduit  6  has a connector  13  within the conduit hanger  8 . The new port  11  is shown above the key groove  10  in the tubing hanger  7 . However in certain instances the new port  11  may be below the key groove  10 . This changes the internal detail of the conduit hanger  8 , but not the overall principle of the invention. A further profile  12  is included in the conduit hanger  8  to allow a tubing hanger plug to be installed within the conduit hanger  8 . This allows the well to be isolated without removing the conduit  6  and conduit hanger  8 . Once the conduit hanger  8  is installed, the replacement fitting for the tie down bolt  14  is inserted into the bore of the tubing hanger  7  forming an alignment pin  17 , as shown in  FIG. 7 . 
         [0052]    A further assembly  20  is installed above the conduit hanger  8  as shown in  FIG. 8 . Assembly  20  contains the communication sub  18 , in which is formed a j-slot, which interacts with the alignment pin  17  to align port  21  with the pin. Additionally, the sub  18  has axial float, to facilitate the alignment with the pin  17 . 
         [0053]    To complete the conduit a sleeve  19 A within the port fitting is moved to interact with the communication sub  18 . Once extended, the sleeve  19 B seals with the communication sub  18 , completing the conduit as shown in  FIG. 9 . 
         [0054]    The cross-section as shown in  FIG. 10  shows that there may be one or more ports  21  within the communication sub  18 . Within each port is a check valve  22 , biased to allow injection of fluid from outside the wellhead to the conduit  6 . The check valves  22  prevent injected fluid from leaving the open alignment ports. Flow ports  23  allow produced oil and gas to pass through the communication sub  18  into the wellhead Christmas tree  1  as normal. 
         [0055]      FIG. 11  shows the installed system. 
         [0056]    It can be seen to those skilled in the art that various changes may be made to the features within this embodiment, without departing from the scope of the invention.