Abstract:
A system for providing power to elements down-hole in a subsea well includes a control pod having at least one shuttle valve, a down-hole hydraulically-actuated device having at least one internal porting mechanism in fluid communication with the at least one shuttle valve, a blowout preventer stack connected to the down-hole device, the blowout preventer stack including a first ram and a second ram, and a choke line in fluid communication with an area between the first ram and the second ram. The at least one shuttle valve controls distribution of hydraulic pressure applied through the choke line to the internal porting mechanism for selective distribution of power to the hydraulically-actuated device.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Application No. 60/558,078, entitled, “Subsea Test Tree,” filed Mar. 30, 2004, and to U.S. Provisional Application No. 60/580,474, entitled, “Tools for Completing Subsea Wells,” filed Jun. 17, 2004, each of which is herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to subsea well technology, and specifically to an improved tubing hanger running tool and subsea test tree control system and method of controlling hydraulic/electric tools or equipment used during drilling, testing or completion of a subsea well.  
       BACKGROUND OF THE INVENTION  
       [0003]     A subsea well constructed for producing hydrocarbons consists of a series of concentric drilled and cased bores. The casings typically include sections of threaded and coupled pipes screwed together. The casings are run into the well bore, suspended (landed) in a wellhead attached to the first casing string (referred to as conductor pipe), and cemented in place by circulating cement down the casing and up into the annular area between the casing and well bore.  
         [0004]     In the process of drilling and equipping (completing) a subsea well, it is often necessary to suspend production tubing in the subsea wellhead or christmas tree with a device known as a tubing hanger. The tubing typically consists of sections of threaded and coupled steel pipes similar to casing, but smaller in diameter and usually higher in pressure rating. Unlike casing, the tubing is not cemented in place and therefore can be replaced. In addition to suspending the tubing in the wellhead or in a Christmas tree, the tubing hanger also seals off the annular space between the tubing and the production casing and provides access to down-hole devices such as safety valves, chemical injection ports, down-hole pressure gauges, as well as other devices.  
         [0005]     In some drilling and completion procedures, a subsea well is connected to a floating platform on the surface of the sea through a Blowout Preventer Stack (BOP) and a marine drilling riser. For example, this is often done in performing a Drill Stem Test or a flow test and cleanup for a completed subsea well. During such procedures, a subsea test tree (SSTT) is landed in the wellhead, or subsea tree, for safety purposes. The SSTT is the primary safety device in containing well pressure in the event that the floating drilling vessel is required to disconnect from the well in an emergency.  
         [0006]     The process of running the SSTT is cumbersome and time consuming to the well operator and requires the rental of expensive equipment (i.e. control panel, hydraulic power supply, control umbilical, hose reel, etc.). Along with the drilling rig time associated with rigging up and running the umbilical and strapping it to the work string, this procedure can add five hundred thousand dollars or more to the well cost, depending on the water depth. The cost can include the rental cost of the SSTT itself, the umbilical, and the control panel and hydraulic power system, as well as the rig time to run the SSTT with the umbilical, strapping the umbilical to the tie back string and rigging up the hydraulic control system.  
       SUMMARY OF THE INVENTION  
       [0007]     In general, in an aspect, the invention provides a system for providing power to elements down-hole in a subsea well. The system includes a control pod having at least one shuttle valve, a down-hole hydraulically-actuated device having at least one internal porting mechanism in fluid communication with the at least one shuttle valve, a blowout preventer stack connected to the down-hole device, the blowout preventer stack including a first ram and a second ram, and a choke line in fluid communication with an area between the first ram and the second ram. The at least one shuttle valve controls distribution of hydraulic pressure applied through the choke line to the internal porting mechanism for selective distribution of power to the hydraulically-actuated device.  
         [0008]     Embodiments of the invention may include one or more of the following features. The shuttle valves may be battery activated shuttle valves. The system may include an acoustic signal generator. The shuttle valves may be controlled by an acoustic signal generated by the acoustic signal generator. The shuttle valves can be controlled with electronic signals received by the control pod. The shuttle valves can be electrically controlled. The control pod may include a receiver to decode pressure pulses generated to control the shuttle valves. The down-hole hydraulically actuated device may include a component in at least one of a tubing hanger running tool, a subsea test tree, and a tubing hanger. The blowout preventer stack may include a port positioned between the first ram and the second ram. The choke line can be in fluid communication with the port. The system can include an electronic control panel and a slip ring to provide control commands to the shuttle valves in the control pod.  
         [0009]     Additional aspects of the invention are directed to a method of providing hydraulic and electric power to tools in a subsea test tree system, the system comprising a blowout preventer stack having a first ram and a second ram and a choke line through which hydraulic pressure is provided to a port in the blowout preventer stack. The method includes isolating an area between the first ram and the second ram of the blowout preventer, distributing hydraulic pressure through the choke line to the area between the first ram and the second ram of the blowout preventer, and controlling the distribution of hydraulic pressure through the choke line to a hydraulically-actuated device by actuating shuttle valves.  
         [0010]     Embodiments of the invention may include one or more of the following features. The method may further comprise generating an acoustic signal and controlling the shuttle valves with the acoustic signal. The method may also comprise generating pressure pulses, receiving the pressure pulses in a control pod housing the shuttle valves, and decoding the pressure pulses to control the shuttle valves. The method may include closing the area between the first ram and the second ram above and below an inlet from the choke line and providing a seal for hydraulic fluid in the blowout preventer.  
         [0011]     Various features of the invention may provide one or more of the following capabilities. Using the sealing capabilities of the BOP and the existing hydraulic power and control functions allows the user to avoid having to obtain the umbilical, the control unit and a hydraulic power supply. Also, rig time is lessened due to the elimination of the necessity of hooking up the aforementioned components, as well as the time required to run the umbilical. Savings can be as much as one-half of the standard cost of renting and running a known subsea test tree. Safety is enhanced by the elimination of the control umbilical required in the current SSTT designs.  
         [0012]     Various features of the invention may provide one or more of the following capabilities. In embodiments of the invention, the need for a hose reel, a control umbilical, a hydraulic control panel, a hydraulic power supply and down-hole accumulator are substantially eliminated. The rig time associated with running the control umbilical is also substantially eliminated. The efficiency of the drilling of a subsea well can be more cost effective and safer for the user.  
         [0013]     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings briefly described below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings briefly described below.  
         [0015]      FIG. 1  is a schematic diagram of a floating drilling rig.  
         [0016]      FIG. 2  is a schematic diagram of a Subsea Test Tree/Tubing Hanger Running Tool.  
         [0017]      FIG. 3  is a schematic diagram of an alternative Subsea Test Tree/Tubing Hanger Running Tool.  
         [0018]      FIG. 4  is a schematic diagram of a Subsea Test Tree/Tubing Hanger Running Tool having an electric power ram.  
         [0019]      FIG. 4A  is a magnified schematic diagram of the electric power ram of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     The features and other details of the invention will now be more particularly described with reference to the accompanying drawings. It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention.  
         [0021]     Embodiments of the invention are related to subsea well technology, and specifically to an improved tubing hanger running tool (THRT) and subsea test tree (SSTT). Embodiments of the invention eliminate a control umbilical and associated hydraulic power pack, as well as associated reel and control panel. Embodiments of the invention use a choke and/or kill line of the blowout preventer system (BOP) to supply hydraulic power. Further, embodiments of the invention use battery powered shuttle valves to direct hydraulic fluid through internal piping and ports to perform many functions in a subsea system. Embodiments of the invention supply hydraulic power to the THRT and to the tubing hanger and SSTT through a blowout preventer that is generally employed in the drilling and completion (equipping for production) of a subsea well. Embodiments and portions of the invention can be used for completing a subsea well, flow testing a subsea well, or for purposes other than completing or testing. Other applications of the embodiments will be apparent to those skilled in the art.  
         [0022]     In embodiments of the invention, hydraulic power is provided through a port in the side of the THRT, rather than through a control umbilical. The port is isolated between two pipe rams in the blowout preventer (BOP). Embodiments of the invention further provide closing the pipe rams such that hydraulic power can be supplied to the port through the choke or kill line that is available on standard subsea blowout preventer stacks. Further, battery-powered shuttle valves are used to direct hydraulic fluid through internal piping to functions that require the hydraulic fluid. Shuttle valves are controlled in at least one of a number of ways, including, but not limited to, by acoustic signals, electronic signals, pressure pulse telemetry, and electrically.  
         [0023]     Referring to  FIG. 1 , a schematic of the general arrangement of a floating drilling operation and selected systems therein is shown. A subsea well system  10  includes a floating drilling rig  12  positioned above sea level, and a marine riser  14 , a lower marine riser package  16  and a BOP stack  18 , all positioned below sea level. Subsea wells are built by establishing a wellhead housing on a conductor casing pipe, and with a blowout preventer stack  18  installed, drilling a well bore down to the producing formation and installing concentric casing strings, which are cemented at the lower ends and sealed with mechanical seal assemblies at each string&#39;s upper end. The lower marine riser  16  is a sub-system of the blowout preventer stack  18 , and allows the rig and riser system to be disconnected from the BOP stack in the event an emergency disconnect is required. The system depicted is a guide-lineless system. Other systems, including systems that utilize guide lines, are known in the art.  
         [0024]     In order to equip the cased well for production, a tubing string is run in through the BOP  18  and a tubing hanger is landed in the wellhead. Thereafter, the BOP stack  18  is removed and replaced by a tree having one or more production bores extending vertically to respective lateral production fluid outlet ports in the wall of the tree. In an alternate embodiment, the tubing hanger may be landed in a subsea christmas tree mounted on the wellhead. The tubing hanger is generally installed by using a hydraulically activated tubing hanger running tool.  
         [0025]     To equip the well for production, a tubing hanger running tool (THRT)  26  and a subsea test tree (SSTT)  28  may be employed. Referring to  FIG. 2 , components that may be used with the THRT  26  and SSTT  28  include a hose reel  30 , a hydraulic power pack  32 , an electro-hydraulic control panel  34 , an electro-hydraulic control umbilical  36 , a flow control head  38 , a BOP control panel  40 , a choke line  42 , a BOP control umbilical  44 , a marine riser  14 , an accumulator  46  for the THRT and the SSTT, a control pod  48  for the THRT and the SSTT, a retainer valve  50 , a hydraulic disconnect  52 , a ball joint  54 , an annular BOP  56 , BOP pipe rams  58  and a tubing hanger  60 . The tubing hanger  60  is connected to the THRT  26 , the umbilical  36  is connected to the control pod  48 , and the assembly is run into the well through the drilling riser  16  and blowout preventer stack  18 , which are attached to the wellhead. Alternatively, the BOP  56  may be landed on the subsea christmas tree, and the tubing hanger may be run and landed in the subsea christmas tree. The THRT  26  and the SSTT  28  can be run together or separately.  
         [0026]     The THRT  26  provides several functions, including but not limited to: facilitating “soft landing” features of the tubing hanger; testing of the various tubing hanger seals; and actuating locking rings to lock the tubing hanger in place. These functions may be actuated by hydraulic pressure delivered to the THRT  26  from the surface vessel (e.g., the floating production platform or drilling rig  12 ) through the control umbilical  36  connected to the dedicated hydraulic power unit  32  on the surface vessel  12 , and operated with the hydraulic control panel  34 . Generally, the control umbilical  36  system transfers high and low pressure fluid supply, annulus fluids and electrical power/signals to the BOP, subsea tree and other equipment down-hole.  
         [0027]     The SSTT  28  has hydraulically actuated valves that are powered and controlled through the electro-hydraulic control line  36  running from the surface platform  12  to the SSTT  28 . The system is run on a high pressure riser, or tie back string  63 , run inside the marine riser  14  and landed and sealed inside the wellhead or subsea tree. The control umbilical  36  is strapped to the tieback string  63 . A surface tree is hooked up to the tie back string to control the flow of the well and allow wireline lubricator access to the well for wireline work. The SSTT  28  cuts the wireline, seals the well, and releases the tie back string in the event that the platform is required to disconnect from the well, for example, in an emergency.  
         [0028]     Referring to  FIG. 3 , the electro-hydraulic control panel  34 , power pack  32 , hose reel  30  and electro-hydraulic umbilical  36  of the system of  FIG. 2  can be replaced by an electronic control panel  61  and a slip ring  62  around the running string  64 . The system of  FIG. 3  operates without a down-hole accumulator. The system includes the retainer valve  50 , the hydraulic disconnect  52 , the control pod  48 , the pipe rams  58 , the SSTT  28  and the THRT  26 . The electronic control panel  61  and the slip ring  62  provide the control commands (e.g., electronically, electrically, acoustically, etc.) to the battery operated shuttle valves in the control pod  48 . The shuttle valves direct/control hydraulic power fluid to the various functions of the THRT  26 , the tubing hanger  60  and the SSTT  28 .  
         [0029]     The hydraulic power in the system of  FIG. 3  is provided via a choke/kill line  42 . The control pod  48  includes a series of shuttle valves  68 . The series of shuttle valves  68  in the control pod  48  for the THRT/SSTT are manifolded to hydraulic power supplied through internal porting in the THRT  26  and the SSTT  28 . The hydraulic power is supplied through the choke or kill line  42  via a port in the THRT  26 . The port is spaced between the lower two pipe rams  58  in the BOP stack  18 . For example, the rams  58  are closed, which isolates the port so the port can receive hydraulic power from the choke/kill line  42 . The choke or kill line  42  is generally approximately 3 inches in diameter; however, other dimensions are possible and envisioned. The hydraulic power can have sufficient capacity/volume so as to substantially eliminate the need for a down-hole accumulator.  
         [0030]     Control of the hydraulic power fluid to the various functions to be operated is through the internal manifold and shuttle valves  68  in the control pod  48 . The lower pipe rams  58  are closed above and below the inlet from the kill line to provide a seal for the hydraulic power fluid to enter a port in the THRT  26 . The port is connected to the internal manifold and shuttle valves.  
         [0031]     When actuated, the shuttle valves  68  direct hydraulic power to the various functions in the tubing hanger/THRT/SSTT. These functions include, but are not limited to, soft landing, seal testing, and a tubing hanger lockdown function.  
         [0032]     A hydraulic passage can be made from the THRT  26 , through the tubing hanger and, by using galley seals, is connected with a passageway through the subsea christmas tree. On the outside of the tree an additional manifold of shuttle valves  68  distributes the hydraulic power to the various hydraulically activated tree functions (valves, connectors, test ports, etc.) The shuttle valves  68  may be battery activated and controlled, as described below. In this way, the tree can be functioned/operated without the need for a separate electrical umbilical.  
         [0033]     The shuttle valves  68  in the control pod  48  are battery operated, for example. Battery power to the shuttle valves  68  can be controlled in a number of ways, now discussed for simplicity in terms of shuttle valve controls. The battery pack for the shuttle valves  68  may be controlled by acoustic signal through the water (or work string). The signal is picked up and decoded by a receiver in the control pod  48  and the shuttle valves are then actuated by electric impulse from the decoder. Electric power is provided by a battery pack in the control pod for the SSTT  28  and the THRT  26 .  
         [0034]     Referring to  FIGS. 4 and 4 A, a separate set of rams  58  in the BOP stack  18  can be used to provide electric power to the control pod  48 . The BOP includes the rams  58 ,  59 , a power sub  72  having insulation  74  and split lines  76  that provide electrical power from the BOP control umbilical  44 . The opposing rams  58 ,  59  include electrodes  70  horizontally opposed but offset in the vertical plane. Electric power is supplied from the control umbilical  44  for the BOP stack  18 . The configuration shown in  FIG. 4A  is non-orienting and transmits electric power through anodes in the ram body to the power sub in the running string. The annulus in the BOP stack  18  is filled with a non-conductive fluid circulated into place through the choke or kill line. Pressure on the rams  58 ,  59  as they close around the power sub squeezes out the non-conductive fluid and makes the electrical connection. An orienting device can be used in the wellhead and BOP stack  18 . Wet mate-able electrical connectors can be used in the rams  58  and the power sub.  
         [0035]     In alternatives of the embodiments described herein, the principle applied to the control pod, THRT and SSTT can also be applied to a christmas tree running tool. In the case of a christmas tree running tool, the hydraulic power may be supplied through the tree running/landing string. The tree running tool (CTRT) is hydraulically locked to the tree, and hydraulic passages connect from a manifold in the CTRT, through the tree to another manifold external to the tree, thence to the various tree functions. Hydraulic power through both hydraulic manifolds may be controlled by battery operated shuttle valves. The shuttle valves are controlled according to at least one of the various methods discussed above.  
         [0036]     In embodiments of the invention, the battery operated shuttle valves are controlled by acoustic signals and acoustic decoder. Alternatively, the shuttle valves  68  are controlled by pressure pulse telemetry as is used in “logging while drilling” (LWD) tools. The coded series of pressure pulses is generated on the surface and decoded by a receiver in the control pod  48 . The receiver directs electric power, from a battery pack in the control pod  48 , to the shuttle valves  68 . A further alternative method by which to control the shuttle valves  68  is by a special landing string containing an electric conductor embedded in or attached to the wall of the pipe. In this method the electric power is supplied directly to the shuttle valves  68  through a multiplexing system similar to a multiplex system for controlling production from subsea wells. A still further alternative includes controlling the shuttle valves by use of a landing string employing an electronic signal transmission wire attached to or embedded in the pipe to control battery powered shuttle valves  68  in the control pod  48 . For example, Grant Prideco&#39;s product Intellipipe™ can be used to provide an electronic signal transmission. Any other method of delivering a signal to a battery pack power supply in order to activate the shuttle valves  68  without the use of an umbilical connection to the down-hole tools is possible and envisioned.  
         [0037]     From the foregoing detailed description it has been shown how the objects of the invention have been obtained in a preferred manner. However, modifications and equivalence of the disclosed concepts such as those which would occur to one of ordinary skill in the art are intended to be included within the scope of the present invention. Such equivalents are considered to be within the scope of the present invention.  
         [0038]     Various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims. Other aspects, advantages, and modifications are within the scope of the invention. The contents of all references, issued patents, and published patent applications cited throughout this application are hereby incorporated by reference. The appropriate components, processes, and methods of those patents, applications and other documents may be selected for the present invention and embodiments thereof.