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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of provisional application U.S. Ser. No. 60/522,500 filed Oct. 7, 2004. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention generally relates to subsurface safety valves. More particularly, the present invention relates to an apparatus and method to install a replacement safety valve to a location where a previously installed safety valve is desired to be replaced. More particularly still, the present invention relates to communicating with a production zone through a bypass-conduit when a replacement safety valve is closed. 
         [0003]    Subsurface safety valves are typically installed in strings of tubing deployed to subterranean wellbores to prevent the escape of fluids from one production zone to another. Absent safety valves, sudden increases in downhole pressure can lead to catastrophic blowouts of production and other fluids into the atmosphere. For this reason, drilling and production regulations throughout the world require safety valves be in place within strings of production tubing before certain operations can be performed. 
         [0004]    One popular type of safety valve is known as a flapper valve. Flapper valves typically include a flow interruption device generally in the form of a circular or curved disc that engages a corresponding valve seat to isolate one or more zones in the subsurface well. The flapper disc is preferably constructed such that the flow through the flapper valve seat is as unrestricted as possible. Usually, flapper-type safety valves are located within the production tubing and isolate one or more production zones from the atmosphere or upper portions of the wellbore or production tubing. Optimally, flapper valves function as large clearance check valves, in that they allow substantially unrestricted flow therethrough when opened and completely seal off flow in one direction when closed. Particularly, production tubing safety valves can prevent fluids from production zones from flowing up the production tubing when closed but still allow for the flow of fluids and/or tools into the production zone from above. 
         [0005]    Flapper valve disks are often energized with a biasing member (spring, hydraulic cylinder, etc.) such that in a condition with zero flow and with no actuating force applied, the valve remains closed. In this closed position, any build-up of pressure from the production zone below will thrust the flapper disc against the valve seat and act to strengthen any seal therebetween. During use, flapper valves are opened by various methods to allow the free flow and travel of production fluids and tools therethrough. Flapper valves may be kept open through hydraulic, electrical, or mechanical energy during the production process. 
         [0006]    Examples of subsurface safety valves can be found in U.S. Provisional Patent Application Ser. No. 60/522,360 filed Sep. 20, 2004 by Jeffrey Bolding entitled “Downhole Safety Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,498 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding entitled “Downhole Safety Valve Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,499 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding entitled “Downhole Safety Valve Interface Apparatus and Method;” all hereby incorporated herein by reference. Furthermore, applicant incorporates by reference U.S. Non-Provisional application Ser. No. 10/708,338 Filed Feb. 25, 2004, titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve” and U.S. Provisional Application Ser. No. 60/319,972 Filed Feb. 25, 2003 titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve.” 
         [0007]    Over time, a replacement subsurface safety valve may be desired. An existing subsurface safety valve can become stuck or otherwise inoperable either through failure of various safety valve components or because of caked-up hydrocarbon deposits, for example. In these circumstance, sudden increases in production zone pressure can lead to dangerous surface blowouts if the safety valves are not repaired. Because the repair or replacement of a subsurface safety valve formerly required the removal of the string of production tubing from the wellbore, these operations were frequently prohibitively costly for marginal wells. An improved apparatus and method to repair or replace existing subsurface safety valves would be highly desirable to those in the petroleum production industry. 
       SUMMARY OF THE INVENTION 
       [0008]    In one embodiment, a replacement safety valve to hydraulically isolate a lower zone below the replacement safety valve from a first bore of an existing safety valve comprises a main body having a clearance passage through a longitudinal bore and an outer profile, the outer profile removably received within a landing profile of the existing safety valve, a flow interruption device located in the clearance passage pivotably operable between an open position and a closed hydraulically sealed position, and a bypass-conduit extending from a surface location through the replacement safety valve to the lower zone, the bypass-conduit wholly contained within a second bore of a string of tubing carrying the existing safety valve. 
         [0009]    In another embodiment, the bypass-conduit can be in communication with the surface location and the lower zone below the valve when the flow interruption device is in the closed hydraulically sealed position. The bypass-conduit can be in communication with the surface location and the lower zone below the valve when the flow interruption device is in the open position. The lower zone can be a production zone. 
         [0010]    In yet another embodiment, the bypass-conduit passes through the existing safety valve en route to the lower zone. The main body can retain a second flow interruption device of the existing safety valve in an open position. The existing safety valve can include a first hydraulic conduit in communication with the replacement safety valve through a second hydraulic conduit therein. The existing safety valve can include a nipple profile. 
         [0011]    In yet another embodiment, the replacement safety valve of claim can further comprise hydraulic seals hydraulically isolating the replacement safety valve from the existing safety valve. The bypass-conduit can extend through the main body of the replacement safety valve. The bypass-conduit can be a hydraulic fluid passage, a continuous string of tubing, or a hydraulic capillary tube. The hydraulic capillary tube can be a fluid injection hydraulic capillary tube. The fluid can be a foam or a gas. The fluid can be selected from the group comprising surfactant, acid, miscellar solution, corrosion inhibitor, scale inhibitor, hydrate inhibitor, and paraffin inhibitor. 
         [0012]    In another embodiment, the bypass-conduit can be a logging conduit, a gas lift conduit, an electrical conductor, or an optical fiber. The bypass-conduit can further comprise a check valve below the replacement safety valve. The bypass-conduit can further comprise a check valve between the replacement safety valve and a wellhead. The bypass-conduit can further comprise a hydrostatic valve between the replacement safety valve and a wellhead. The bypass-conduit can further comprise a hydrostatic valve below the replacement safety valve. 
         [0013]    In another embodiment, the replacement safety valve further comprises an operating conduit in communication with a source of an energy, the energy actuating the flow interruption device between the open position and the closed hydraulically sealed position. The operating conduit can extend from the surface location through the first bore of the existing safety valve to the main body. The operating conduit can extend from the surface location to the replacement safety valve through a wall of the existing safety valve. 
         [0014]    In yet another embodiment, a method to hydraulically isolate a zone below an existing safety valve from a string of tubing carrying the existing safety valve in communication with a surface location comprises deploying a replacement safety valve through the string of tubing to a location of the existing safety valve, engaging the replacement safety valve within a landing profile of the existing safety valve, extending a bypass-conduit from the surface location, through the replacement safety valve, to the zone below the existing safety valve, and communicating between the surface location and the zone below the existing safety valve through the bypass-conduit when a flow interruption device of the replacement safety valve is in a closed hydraulically sealed position. The zone below the existing safety valve can be a production zone. 
         [0015]    In another embodiment, a method can further comprise the step of communicating between the surface location and the zone below the existing safety valve through the bypass-conduit when the flow interruption device of the replacement safety valve is in an open position. A method can further comprise the step of retaining a second flow interruption device of the existing safety valve in an open position with an outer profile of the replacement safety valve. The bypass-conduit can be a hydraulic fluid passage, a continuous tube, or a hydraulic capillary tube. The bypass-conduit can comprise a plurality of a jointed pipe section deployed from the surface location. A method can further comprise the step of including a check valve in the bypass-conduit above the replacement safety valve or below the replacement safety valve. 
         [0016]    In another embodiment, a method can further comprise the step of injecting a foam or a fluid to the zone below the existing safety valve through the bypass-conduit. The fluid can be selected from the group consisting of corrosion inhibitor, scale inhibitor, hydrate inhibitor, paraffin inhibitor, surfactant, acid, and miscellar solution. The bypass-conduit can be a logging conduit. The logging conduit can be greater than about one and a half inches in diameter. A method can include a bypass-conduit which can be a gas lift conduit, an electrical conductor, or an optical fiber. 
         [0017]    In yet another embodiment, the method can further comprise the step of operating the flow interruption device between the closed hydraulically sealed position and an open position with an operating conduit. The method can further comprise the step of extending the operating conduit from the surface location to the replacement valve through the string of tubing. The method can further comprise the step of communicating hydraulic pressure through the operating conduit, through a first passage in the existing safety valve to a second passage in the replacement safety valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is schematic representation of a replacement safety valve assembly installed in an existing safety valve in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring initially to  FIG. 1 , a schematic representation of a replacement subsurface safety valve assembly  100  is shown engaged within an existing subsurface safety valve  102 . Existing safety valve  102  includes a generally tubular valve body  104 , a flapper  106 , a landing profile  108 , and a clearance bore  110 . Likewise, replacement valve assembly  100  includes a main body  112 , an engagement profile  114 , a flapper  116 , and a clearance bore  118 . 
         [0020]    With a replacement safety valve desired to be located within an existing safety valve  102 , replacement valve assembly  100  is disposed downhole through the string of tubing or borehole where preexisting safety valve  102  resides. Once replacement valve  100  reaches existing safety valve  102 , replacement valve  100  is actuated through clearance bore  110  until engagement profile  114  of replacement valve  100  engages and locks within landing profile  108  of existing safety valve  102 . Landing and engagement profiles  108 ,  114  are shown schematically in  FIG. 1  but any scheme for mounting a tubular or a valve downhole known to one of ordinary skill in the art may be used. 
         [0021]    For example, to lock into place replacement subsurface safety valve assembly  100  within landing profile  108  of existing safety valve  102 , engagement profile  114  can be constructed with a collapsible profile, a latching profile, or as an interference-fit profile. In an interference-fit scheme (as shown schematically in  FIG. 1 ), the outer diameter of engagement profile  114  is slightly larger than the diameter of the clearance bore  110  but slightly smaller than a minimum diameter of landing profile  108  of existing safety valve  102 . Using this scheme, replacement valve  100  is engaged within clearance bore  110  until engagement profile  114  abuts valve body  104 . Once so engaged, replacement valve  100  can be impact loaded until engagement profile  114  travels through clearance bore  110  and engages within landing profile  108 . Alternatively, engagement profile  114  can be constructed to be retractable or extendable via wireline or hydraulic capillary such that the full dimension of engagement profile  114  is not reached until it is in position within landing profile  108 . 
         [0022]    Once installed, replacement valve body  112  opposes any biasing force remaining to retain flapper  106  of existing safety valve  102  out of the way within recess  120 . Hydraulic seals  122 ,  124 , and  126  isolate fluids flowing from production zones below valves  100 ,  102  through clearance bores  118 ,  110  from coming into contact with, and eroding components ( 106 ,  120 ) of existing safety valve  102  and the outer profile of replacement valve  100 . Otherwise, paraffin and other deposits might clog the space defined between valve bodies  112  and  104  and could prevent subsequent repair or removal operations of either replacement valve  100  or existing safety valve  102 . 
         [0023]    In operation, fluids will flow from downhole zone  130 , through clearance bore  118  of replacement valve  100 , and through upper end of clearance bore  110  of existing safety valve  102  to upper zone  132 . Typically, downhole zone  130  will be a production zone and upper zone  132  will be in communication with a surface station. Flapper  116  of replacement valve  100  pivots around axis  134  between an open position (shown) and a closed position (shown by dashed lines in  FIG. 1 ). A valve seat  136  acts as a stop and seals a surface of flapper disc  116  to prevent hydraulic communication from lower zone  130  to upper zone  132  when flapper  116  is closed. With flapper  116  closed, increases in pressure in lower zone  130  act upon the bottom of and thrust flapper  116  against seat  136  with increased pressure to enhance any hydraulic seal therebetween. Typically, a torsional spring (not shown) acts about axis  134  to bias flapper disc  116  against seat  136  if not held open by some other means. Various schemes can be and have been employed to retain flapper  116  in an open position when passage from lower zone  130  to upper zone  132  is desired (or vice versa), including using a slidable operating mandrel or a hydraulic actuator housed within valve body  112 . Regardless of how activated from open to closed position, flapper  116  acts to prevent communication from lower zone  130  to upper zone  132  when closed. 
         [0024]    Additionally, replacement valve  100  can optionally be configured to have flapper  116  or any other component operated from the surface. An operating conduit (not shown) can optionally be deployed from a surface unit, through tubing and existing safety valve  102  to replacement valve  100  to operate flapper  116  from closed position to open position (or vice versa). Furthermore, referring again to  FIG. 1 , an existing operating conduit  140  emplaced with existing safety valve  102  can be used to operate flapper  116  of replacement valve  100 . Specifically, operating conduit  140  extends from a surface location to existing safety valve  102  to operate flapper disc  106 . While operating conduit  140  is shown schematically as a hydraulic conduit, it should be understood by one of ordinary skill in the art that any operating scheme including, electrical, mechanical, pneumatic, and fiber optic systems can be employed. A passage  142  connects operating conduit  140  to inner bore  110  of existing safety valve  102  to allow operating conduit  140  to communicate with replacement valve  100  through a corresponding passage  144 . A pressure accumulator  146  is housed within main body  112  of replacement valve  100  and acts to store and convert pressure from operating conduit  140  into mechanical energy to displace flapper  116  between open and closed positions. Hydraulic seals  124 ,  126  ensure that any pressure in operating conduit  140  is maintained through passages  142 ,  144  and accumulator  146  with little or negligible loss. To prevent operating conduit  140  from communicating with bore  110  of existing safety valve  102  before replacement valve  100  is present, a rupture disc (not shown) can be placed within passage  142 . Rupture disc can be configured to rupture at a pressure that is outside the normal operating range of existing safety valve  102 . To install replacement valve  100 , an operator increases pressure in operating conduit  140  to “blow out” rupture disc in passage  142  and then can install replacement valve  100 . Once rupture disc is ruptured, operating conduit  140  can be used as normal to operate flapper  116  of replacement valve  100 . 
         [0025]    It is often desirable to communicate with lower zone  130  when flapper valve  116  is closed. For instance, there are circumstances where pressures within producing zones are such as to not allow the opening of flapper  116  but the injection of chemical, foam, gas, and other material to lower zone  130  is either beneficial or necessary. To accommodate such situations, a bypass-conduit  150  can be incorporated in replacement valve  100  such that communication between upper zone  132  and lower zone  130  can occur irrespective of the position of flapper  116 . The upper zone  132  can be a surface location. Bypass-conduit  150  includes an upper segment  152 , a lower segment  154 , and a passage  156  through replacement valve body  112  of replacement valve  100 . Bypass-conduit  150  can be of any form known to one of ordinary skill in the art, but can be a single continuous hydraulic tube, a string of threaded tubing sections, an electrical conduit, a fiber-optic conduit, a gas lift conduit, or, depending of the size of replacement valve  100 , a logging conduit. Typically, bypass-conduit  150  will most often be constructed as hydraulic capillary tubing allowing the injection of a chemical stimulant, surfactant, inhibitor, solvent, and foam from a surface location to lower zone  130 . 
         [0026]    Furthermore, if bypass-conduit  150  is constructed to allow the injection of fluid to lower zone  132  from above, a check valve (not shown) may be included to prevent increases in downhole pressure from blowing out past replacement valve  100  through bypass-conduit  150  to the surface. The term capillary tube is used to describe any small diameter tube and is not limited to a tube that holds liquid by capillary action nor is there any requirement for surface tension to elevate or depress the liquid in the tube. The term hydraulic and hydraulically are used to describe water or any other fluid and are not limited to a liquid or by liquid means, but can be a gas or any mixture thereof. 
         [0027]    While the invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.

Summary:
A safety valve ( 100 ) replaces an existing safety valve ( 102 ) in order to isolate a production zone from a tubing string when closed. Preferably the safety valve ( 100 ) includes a flow interruption device ( 106 ) displaced by an operating conduit extending from a surface location to the safety valve ( 100 ) through the inside of the production tubing. A by-pass conduit ( 150 ) allows communication from a surface location to the production zone through the safety valve ( 100 ) without affecting the operation of the safety valve ( 100 ).