Abstract:
A system and method for communicating hydraulic control to a wireline retrievable downhole device ( 112 ) are disclosed. The system utilizes a tubing retrievable downhole device ( 50 ) having a hydraulic chamber ( 70 ). A radial cutting tool ( 104 ) is selectively located within the tubing retrievable downhole device ( 50 ) to cut a fluid passageway ( 110 ) between the hydraulic chamber ( 70 ) and the interior of the tubing retrievable downhole device ( 50 ). Thereafter, when the wireline retrievable downhole device ( 112 ) is positioned within the tubing retrievable downhole device ( 50 ), hydraulic control is communicated to the wireline retrievable downhole device ( 50 ) through the fluid passageway ( 110 ) to actuate the wireline retrievable downhole device ( 50 ).

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates in e, to the operation of hydraulically controllable downhole devices and in particular to a system and method for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole device. 
     BACKGROUND OF THE INVENTION 
     One or more subsurface safety valves are commonly installed as part of the tubing string within oil and gas wells to protect against the communication of high pressure and high temperature formation fluids to the surface. These subsurface safety valves are designed to shut in production from the formation in response to a variety of abnormal and potentially dangerous conditions. 
     As one or more subsurface safety valves are built into the tubing string, these valves are typically referred to as tubing retrievable safety valves (“TRSV”). TRSVs are normally operated by hydraulic fluid pressure. The hydraulic fluid pressure is typically controlled at the surface and transmitted to the TRSV via a hydraulic fluid line. Hydraulic fluid pressure must be applied to the TRSV to place the TRSV in the open position. When hydraulic fluid pressure is lost, the TRSV will operate to the closed position to prevent formation fluids from traveling therethrough. As such, TRSVs are fail safe valves. 
     As TRSVs are often subjected to years of service in severe operating conditions, failure of TRSVs may occur. For example, a TRSV in the closed position may leak. Alternatively, a TRSV in the closed position may not properly open. Because of the potential for disaster in the absence of a properly functioning TRSV, it is vital that the malfunctioning TRSV be promptly replaced or repaired. 
     As TRSVs are typically incorporated into the tubing string, removal of the tubing string to replace or repair the malfunctioning TRSV is required. Depending on the circumstances, the cost of pulling the tubing string out of the wellbore can run into the millions of dollars. 
     It has been found, however, that a wireline retrievable safety valve (“WRSV”) may be inserted inside the original TRSV and operated to provide the same safety function as the original TRSV. These valves are designed to be lowered into place from the surface via wireline and locked in place inside the original TRSV. This method is a much more efficient and cost-effective alternative to pulling the tubing string. 
     If the WRSV is to take over the full functionality of the original TRSV, the WRSV must be communicated to the hydraulic control system. In traditional TRSVs, the communication path for the hydraulic fluid pressure to the replacement WRSV is established through a pre-machined radial bore extending from the hydraulic chamber to the interior of the TRSV. Once a failure in the TRSV has been detected, this communication path is established by shifting the TRSV to its locked out position and sheering a sheer plug that is installed within the radial bore. 
     It has been found, however, that operating conventional TRSVs to the locked out position and establishing this communication path has several inherent drawbacks. To begin with, the communication path creates a leak path for formation fluids up through the hydraulic control system. As noted above, TRSVs are intended to operate under abnormal well conditions and serve a vital and potentially life-saving function. Hence, if such an abnormal condition occurred when one TRSV has been locked out, even if other safety valves have closed the tubing string, high pressure formation fluids may travel to the surface through the hydraulic line. In addition, manufacturing a TRSV with this radial bore requires several high-precision drilling and thread tapping operations in a difficult-to-machine material. Any mistake in the cutting of these features necessitates that the entire upper subassembly of the TRSV be scrapped. The manufacturing of the radial bore also adds considerable expense to the TRSV, while at the same time reducing reliability of the finished product. For example, if the seal between the sheer plug and the radial bore fails, a communication path for formation fluids may be created between the annulus and the interior of the TRSV. Additionally, this added expense and complexity must be built into every installed TRSV, while it will only be put to use in some small fraction thereof. 
     Therefore, a need has arisen for a system and method for establishing a communication path for hydraulic fluid pressure to a WRSV from a failed TRSV. A need has also arisen for such a system and method that does not create the potential for formation fluids to travel up through the hydraulic control line. Further, a need has arisen for such a system and method that does not require the complexity, expense, leak potential and reliability concerns associated with manufacturing a TPSV with a radial bore having a sheer plug therein. 
     SUMMARY OF THE INVENTION 
     The present invention disclosed herein comprises a system and method for establishing a communication path for hydraulic fluid pressure to a wireline retrievable downhole device from a tubing retrievable downhole device. The system and method of the present invention avoids the potential for formation fluids to travel up through the hydraulic control line. The system and method of the present invention also avoids the complexity, expense, leak potential and reliability concerns associated with a pre-drilled radial bore in the tubing retrievable downhole device that requires a sheer plug to be disposed therein to provide a seal. 
     The system of the present invention for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole utilizes a tubing retrievable downhole device having a hydraulic chamber. After a malfunction of the tubing retrievable downhole device is detected and a need exists to otherwise achieve the functionality of the tubing retrievable downhole device, a radial cutting tool may be selectively located within the tubing retrievable downhole device. The radial cutting tool is used to create a fluid passageway between the hydraulic chamber of the tubing retrievable downhole device and the interior of the tubing retrievable downhole device. As such, hydraulic fluid may now be communicated down the existing hydraulic lines to the interior of the tubing. Once this communication path exists, the wireline retrievable downhole device may be positioned within the tubing retrievable downhole device such that the hydraulic fluid pressure from the hydraulic system may be communicated to the wireline retrievable downhole device. 
     The radial cutting tool that is selectively located within the tubing retrievable downhole device may be a chemical cutting tool, a mechanical cutting tool, explosive cutting mechanism or the like that are well known in the art. 
     In one embodiment of the present invention, the tubing retrievable downhole device may be a tubing retrievable safety valve that is operated to the lock out position prior to creating the fluid passageway between the hydraulic chamber of the tubing retrievable safety valve and the interior of the tubing retrievable safety valve. In this embodiment of the present invention, the wireline retrievable downhole device is typically a wireline retrievable safety valve that is used to replace the functionality of a malfunctioning tubing retrievable safety valve. 
     The method of the present invention for communicating hydraulic control from a tubing retrievable downhole device to a wireline retrievable downhole device involves locating a radial cutting tool within the tubing retrievable downhole device, creating a fluid passageway from the hydraulic chamber of the tubing retrievable downhole device to the interior of the tubing retrievable downhole device with the radial cutting tool and positioning the wireline retrievable downhole device within the tubing retrievable downhole device adjacent to the fluid passageway, thereby communicating hydraulic control to the wireline retrievable downhole device. 
     In the method of the present invention, the step of creating the fluid passageway may be achieved by chemically cutting the fluid passageway, mechanically cutting the fluid passageway, explosively cutting the fluid passageway or the like. 
     The method of the present invention may, for example, be used to communicate hydraulic fluid pressure to actuate a wireline retrievable safety valve that has been positioned within a tubing retrievable safety valve that has been operated to its lock out position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, including its features and advantages, reference is row made to the detailed description of the invention, taken in conjunction with the accompanying drawings in which like numerals identify like parts and in which: 
     FIG. 1 is a schematic illustration of an offshore production platform wherein a wireline retrievable safety valve is being lowered into a tubing retrievable safety valve to take over the functionality thereof; 
     FIG. 2 is a half-section view of a tubing retrievable safety valve in its lock out position; 
     FIG. 3 is a half-section view of a tubing retrievable safety valve having a radial cutting tool positioned therein adjacent to the hydraulic chamber of the tubing retrievable safety valve; 
     FIG. 4 is a half-section view of a tubing retrievable safety valve having a radial cutting tool positioned therein after creating a fluid passageway between the hydraulic chamber of the tubing retrievable safety valve and the interior of the tubing; and 
     FIG. 5 is a half-section view of a tubing retrievable safety valve having a wireline retrievable safety valve disposed therein such that hydraulic control over the wireline retrievable safety valve may be established with the hydraulic system originally utilized to control the tubing retrievable safety valve. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the making and using of various embodiments of the present invention is discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention. 
     Referring to FIG. 1, an offshore oil and gas production platform having wireline retrievable safety valve lowered into a tubing retrievable safety valve is schematically illustrated and generally designated  10 . A semi-submersible platform  12  is centered over a submerged oil and gas formation  14  located below sea floor  16 . Wellhead  18  is located on deck  20  of platform  12 . Well  22  extends through the sea  24  and penetrates the various earth strata including formation  14  to form wellbore  26 . Disposed within wellbore  26  is casing  28 . Disposed within casing  28  and extending from wellhead  18  is production tubing  30 . A pair of seal assemblies  32 ,  34  provide a seal between tubing  30  and casing  28  to prevent the flow of production fluids therebetween. During production, formation fluids enter wellbore  26  through perforations  36  of casing  28  and travel into tubing  30  to wellhead  18 . 
     Coupled within tubing  30  is a tubing retrievable safety valve  38 . As is well known in the art, multiple tubing retrievable safety valves are commonly installed as part of tubing  30  to shut in production from formation  14  in response to a variety of abnormal and potentially dangerous conditions. For convenience of illustration, however, only tubing retrievable safety valve  38  is shown. 
     Tubing retrievable safety valve  38  is operated by hydraulic fluid pressure communicated thereto from surface installation  40  and hydraulic fluid control conduit  42 . Hydraulic fluid pressure must be applied to tubing retrievable safety valve  38  to place tubing retrievable safety valve  38  in the open position. When hydraulic fluid pressure is lost, tubing retrievable safety valve  38  will operate to the closed position to prevent formation fluids from traveling therethrough. 
     If, for example, tubing retrievable safety valve  38  is unable to properly seal in the closed position or does not properly open after being in the closed position, tubing retrievable safety valve  38  must typically be repaired or replaced. In the present invention, however, the functionality of tubing retrievable safety valve  38  may be replaced by wireline retrievable safety valve  44 , which may be installed within tubing retrievable safety valve  38  via wireline assembly  46  including wireline  48 . Once in place within tubing retrievable safety valve  38 , wireline retrievable safety valve  44  will be operated by hydraulic fluid pressure communicated thereto from surface installation  40  and hydraulic fluid line  42  through tubing retrievable safety valve  38 . As with the original configuration of tubing retrievable safety valve  38 , the hydraulic fluid pressure must be applied to wireline retrievable safety valve  44  to place wireline retrievable safety valve  44  in the open position. If hydraulic fluid pressure is lost, wireline retrievable safety valve  44  will operate to the closed position to prevent formation fluids from traveling therethrough. 
     Even though FIG. 1 depicts a cased vertical well, it should be noted by one skilled in the art that the present invention is equally well-suited for uncased wells, deviated wells or horizontal wells. 
     Referring now to FIGS. 2A and 2B, half sectional views of tubing retrievable safety valve  50  are illustrated. Safety valve  50  is connected directly in series with production tubing  30 . Hydraulic control pressure is conducted in communicated to subsurface safety valve  50  via control conduit  42  to a longitudinal bore  52  formed in the sidewall of the top connector sub  54 . Pressurized hydraulic fluid is delivered through the longitudinal bore  52  into an annular chamber  56  defined by a counterbore  58  which is in communication with an annular undercut  60  formed in the sidewall of the top connector sub  54 . An inner housing mandrel  62  is slidably coupled and sealed to the top connector sub  54  by a slip union  64  and seal  66 , with the undercut  60  defining an annulus between inner mandrel  62  and the sidewall of top connector sub  54 . 
     A piston  68  is received in slidable, sealed engagement against the internal bore of inner mandrel  62 . The undercut annulus  60  opens into a piston chamber  70  in the annulus between the internal bore of a connector sub  72  and the external surface of piston  68 . The external radius of an upper sidewall piston section  74  is machined and reduced to define a radial clearance between piston  68  and connector sub  72 . An annular sloping surface  76  of piston  68  is acted against by the pressurized hydraulic fluid delivered through control conduit  42 . In FIGS. 2A-2B, piston  68  is in its locked out position wherein piston  68  is fully extended with the piston shoulder  78  engaging the top annular face  80  of an operator tube  82 . In this locked out position, a return spring  84  is fully compressed. 
     A flapper plate  86  is pivotally mounted onto a hinge sub  88  which is threadably connected to the lower end of spring housing  90 . A valve seat  92  is confined within a counterbore formed on hinge sub  88 . The lower end of safety valve  50  is connected to production tubing  30  by a bottom sub connector  94 . The bottom sub connector  94  has a counterbore  96  which defines a flapper valve chamber  98 . Thus, the bottom sub connector  94  forms a part of the flapper valve housing enclosure. In normal operation, flapper plate  86  pivots about pivot pin  100  and is biased to the valve closed position by coil spring  102 . When subsurface safety valve  50  must be operated from the valve open position to the valve closed position, hydraulic pressure is released from conduit  42  such that return spring  84  acts on the lower end of piston  68  which retracts operator tube  82  longitudinally through flapper valve chamber  98 . Flapper closure plate  86  will then rotate through chamber  98 . In the locked out position as shown in FIGS. 2A-2B, however, the spring bias force is overcome and flapper plate  86  is locked out by operator tube  82 . 
     Even though subsurface safety valve  50  has been depicted, for the purposes of illustration, as having a flapper-type closure plate, it should be understood by one skilled in the art that subsurface safety valve  50  may incorporate various types of valve closure elements. Additionally, even though subsurface safety valve  50  has been depicted, for the purposes of illustration, as having hydraulic fluid acting directly upon piston  68 , it should be understood by one skilled in the art that subsurface safety valve  50  may alternatively incorporate a rod-piston mechanism which is acted upon by the hydraulic fluid and which in turn operates piston  68 . 
     If safety valve  50  becomes unable to properly seal in the closed position or does not properly open after being in the closed position, it is desirable to reestablish the functionality of safety valve  50  without removal of tubing  30 . In the present invention, as depicted in FIGS. 3A-3B, this is achieved by inserting a radial cutting tool  104  into the central bore of safety valve  50 . Radial cutting tool  104  may use any one of several cutting techniques that are well known in the art including, but not limited to, chemical cutting, thermal cutting, mechanical cutting, explosive cutting or the like. 
     For example, radial cutting tool  104  may be a chemical cutter that is lowered through tubing  30  from the surface into the center of the locked out safety valve  50 . An example of a suitable chemical cutter is disclosed in U.S. Pat. No. 5,575,331, which is hereby incorporated by reference. The position of radial cutting tool  104  within safety valve  50  is determined by the engagement of the locator section  106  of radial cutting tool  104  with a landing nipple  108  within tubing  30 . Once in place, radial cutting tool  104  is operated to cut through upper sidewall piston section  74 . In the case of using the chemical cutter, a dispersed jet of cutting fluid is released through cutting ports, making a 360 degree cut into the surrounding material. The chemical cutter is fired by an electrical signal carried by a cable, which is normally controlled at the surface. The depth of cut made by the chemical cutter is predetermined, and is controlled by the composition of chemicals loaded into the chemical cutter and the geometry of the cutting ports. The chemical cutter is set to make a cut deep enough to penetrate through upper sidewall piston section  74  of the piston  68  while still shallow enough to maintain the integrity of connector sub  72 , as best seen in FIGS. 4A-4B. 
     With the use of any suitable radial cutting tool  104 , a fluid passageway  110  is created from piston chamber  70  to the interior of safety valve  50  through upper sidewall piston section  74 . Hydraulic pressure communicated to piston chamber  70  may thereby be communicated to the interior of safety valve  50 . Once fluid passageway  110  is created through upper sidewall piston section  74 , radial cutting tool  104  is retrieved to the surface. As depicted in FIGS. 5A-5B, a wireline retrievable safety valve  112  is then lowered into the central bore of tubing retrievable safety valve  50 . Wireline retrievable valve locator ring  115  engages landing nipple  108  within tubing  30  and locks into place. Installed in this manner, safety valve  112  seals the previously open fluid passageway  110  created by radial cutting tool  104  between seal  114  and seal  116 . Hydraulic control pressure is now conducted to safety valve  112  through fluid passageway  110 . Pressurized hydraulic fluid may now be delivered through an annular chamber  118  defined between piston  68  of safety valve  50  and housing  120  of safety valve  112 . Annular chamber  118  is in communication with a radial port  122  and an annular chamber  124  formed between housing  120  and piston  126  of safety valve  112 . Piston  126  is slidably coupled and sealed to housing  120  by seals  128  and  129 . Piston  126  is fully extended with the piston shoulder  130  engaging the top annular face  132  of an operator tube  134 . In this valve open position, a return spring  136  is fully compressed. 
     A flapper plate  138  is pivotally mounted onto a hinge sub  140 . A valve seat  142  is confined within hinge sub  140 . Flapper plate  138  pivots about pivot pin  144  and is biased to the valve closed position by coil spring  146 . In the valve open position as shown in FIGS. 5A-5B, the spring bias force is overcome and flapper plate  138  is retained in the valve open position by operator tube  134  to permit formation fluid slow up through tubing  30 . 
     When an out of range condition occurs and safety valve  112  must be operated from the valve open position to the valve closed position, hydraulic pressure is released from conduit  44  such that return spring  136  acts on the lower end of piston  126  which retracts operator tube  134  longitudinally through flapper valve chamber  148 . Flapper closure plate  138  will then rotate through chamber  148  and seal against seat  142  to prevent the flow of formation fluids therethrough. As such, safety valve  112  replaces the functionality of safety valve  50  utilizing the hydraulic system originally used to operate safety valve  50 . Thus, with the use of the present invention, hydraulic control may be communicated to a wireline retrievable downhole device through an existing tubing retrievable downhole device without removal of tubing  30 . In addition, with the use of the present invention, hydraulic control may be communicated to a wireline retrievable downhole device through an existing tubing retrievable downhole device without creating unnecessary leak paths or designing complex and expensive tubing retrievable downhole devices. 
     While this invention has been described with a reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.