Abstract:
An electro-hydraulic surface controlled subsurface safety valve is controllable entirely electrically. The actuator operates on an electrically actuated pressure pump and a supply of hydraulic fluid reservoired in the tool proximate to the safety valve. A dump valve is normally open so that if power fails, pressure is released and the safety valve closes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Serial No. 60/084,233 filed May 5, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to surface controlled subsurface safety valves. More particularly, the invention relates to electro-hydraulic actuation systems for such valves. 
     2. Prior Art 
     Surface controlled subsurface safety valves have been used for many years to prevent such occurrences as “blowouts” and other dangerous well conditions. Safety valves are designed so that if they fail, they fail in a safe position so that upon a break in the hydraulic fluid system, conventionally supplied at the surface and extended in a small diameter high pressure tubing line downhole, the power spring in the safety valve closes the flapper of the safety valve. The power spring must be able to lift the hydraulic column to the surface. This requires very strong springs and consequently, high opening pressures for valves set very deeply within the earths crust. 
     More recently, electromechanical actuators have been conceived employing electrically actuated mechanical means to open the flapper. The electromechanical systems are extremely effective for installations in which they are specified but different wells have different requirements and the art is still in need of other types of actuating systems. 
     SUMMARY OF THE INVENTION 
     The prior art need as noted above is alleviated by the electro-hydraulic surface controlled subsurface safety valve operating system of the invention. 
     The electro-hydraulic system employs in its broadest concept, a pump having a fluid supply attached thereto, the pump being connected directly to the safety valve. The pump is operated by a downhole electronics package and/or surface electronics package which controls the pump and additionally powers an electrically controlled dump valve connected to the hydraulic discharge fluid line connected between the pump and the conventional subsurface safety valve. When the solenoid of the dump valve is powered, the dump valve is closed and pressure generated by the pump is transmitted to the safety valve to operate the same. Upon interruption of power whether by design or by happenstance, the solenoid on the dump valve opens and the safety valve shuts, the power spring thereof being powerful enough to move the small amount of hydraulic fluid necessary back into the fluid supply chamber or reservoir through the dump valve. Thus the valve is quickly (about 5 seconds) and easily closed by interrupting power at the surface and additionally closes in the event power is lost for any other reason. 
     An advantage of the system is that it preferentially maintains the hydraulic fluid reservoir downhole and in proximity to the other components of the system. This avoids the long fluid column to the surface that is part of most systems in the prior art. This also eliminates the necessity of a strong power spring when the valve is set deep as the hydraulic column does not extend to the surface. The safety valve power spring needs to lift the weight of moving parts and overcome friction, both known from prior art. 
     Two pump arrangements are contemplated for the system, although other pumping arrangements could be substituted. The system preferably employs a pressure compensated annular reservoir within which the pump, a manifold and dump valve are disposed. Advantages are gained by placing these components in the hydraulic fluid of the reservoir. More specifically, the components are protected from wellbore fluids by the enclosed hydraulic fluid and may thus be constructed from less expensive materials. The pump remains well lubricated and cooled. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIGS. 1-6 are an elongated cross-section view of the motor driven pump embodiment of the invention; 
     FIGS. 7-12 are an elongated cross-section view of the solenoid plunger pump embodiment of the invention; 
     FIG. 13 is a section view taken along section line  13 — 13  in FIG. 9 illustrating the manifold of the invention; 
     FIG. 14 is a perspective broken open view of a solenoid dump valve; and 
     FIG. 15 is a portion of the sleeve of the invention illustrating the T-slot of the invention; 
     FIGS. 16-19 are an elongated view of another embodiment of the invention; 
     FIGS. 16A,  18 A and  18 B are cross section views of the embodiment of FIGS. 16-18 taken at cross section lines as illustrated. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each of the preferred embodiments of the invention employ the reservoir, electronics package and the solenoid dump valve. These elements will be essentially unchanged in both of the embodiments. Additionally, each embodiment includes a means to move the hydraulic fluid under pressure to the safety valve inlet. The two preferred embodiments of this invention each employ one of a motor driven pump and a solenoid plunger pump. 
     Referring to FIGS. 1-6, a first embodiment of the invention is illustrated. This embodiment employs the motor-driven hydraulic pump arrangement as the fluid moving component. 
     Referring first to FIG.  1  and moving sequentially through FIG. 6, the invention comprises electronics housing  12  having preferably an uphole premium thread connection for connecting the system of the invention to a string of pipe (not shown). Electronics housing  12  supports electronics package  20  within an annular space  22  preferably filled with nitrogen and which is defined radially inwardly by housing  12  and radially outwardly by electronics cover  18 . The gas contained in the space  22  is maintained therein by a seal  14  and snap ring  16  at the uphole end of the electronics cover  18  while the downhole end of the cover  18  is sealed by premium threaded connections which connect the electronics sub to the intermediate sub  24 . As is readily appreciated from a review of the drawing FIG. 2, electronics housing  12  is connected to intermediate sub  24  by preferably a premium thread  26  at the radially inward extent thereof, while the cover  18  is connected to intermediate sub  24  by a premium threaded connection  28 . 
     Intermediate sub  24  is employed for manufacturability reasons and supports a through bore  30  having a connector part  32  at the uphole end thereof which preferably is constructed to receive a Kemlon connector (not shown). Bore  30  provides passage for a current carrying conduit (not shown) to power the pump and solenoid dump valve discussed hereunder. 
     Attached at the downhole end of intermediate sub  24  by preferably a premium threaded connection  34  is pump housing  36 . Pump housing  36  extends downhole to connect with a cylinder sub  96  of a conventional surface controlled subsurface safety valve (SCSSV) by preferably a premium threaded connection  98 . Pump housing  36  contains in an annular space  38 , between it and compensator piston  40 , which space  38  is sealed by a large dynamic seal  42 , retained by retainer  44  and by small dynamic seal  52 , retained by manifold  54 . Also contained in the annular space  38  are motor  46  connected to hydraulic pump  48  which then is connected to discharge connector  50  and mounted to manifold  54 . Annular space  38  is, in a preferred embodiment, also the reservoir for the hydraulic fluid supply employed to open the conventional components of the SCSSV. The space  38  contains the components noted as well as the manifold  54  to advantageously bathe the components in the hydraulic fluid in a preferred embodiment. 
     Significant benefits are realized by placing all of the components noted directly in the reservoir space  38 . These benefits include reduction of length of the tool (more than one function contained in a single space), longevity increase of the bathed components (no deleterious effects from well bore fluids) and the ability to use more economical materials such as stainless steel instead of expensive materials such as inconel which would be necessary if the manifold were in contact with wellbore fluids. Space  38  is pressure compensated to wellbore pressure by compensating piston  40  which employs a large end and a small end corresponding to the large and small seals identified above to render the piston dynamic. Preferably seal  42  is a spring-loaded Teflon seal, commercially available from Greene, Tweed &amp; Co. and seal  52  is a spring-loaded Teflon seal, commercially available from Greene, Tweed and Co. A conventional elastomeric material may be substituted for dynamic sealing. 
     Motor  46  is preferably a DC brushless type motor which is available commercially from many sources. Hydraulic pump  48  is a radial piston type pump and is also commercially available from many sources. 
     Referring to FIG. 3, pump  48  is preferably threadedly connected to discharge connector  50  so that pressurized discharge fluid from pump  48  is transferable through manifold  54  to the honed seal bore  70  of the conventional SCSSV. In the cross-section views of FIG.  3  and FIG. 13, it is possible to view recess  56  having metal seal bore  58 . Recess  56  connects to fluid port  62  for communication through manifold  54  to fluid hone bore  70 . Referring to FIG. 13 directly, other aspects of manifold  54  are illustrated. 
     In FIG. 13 the manifold  54  is illustrated from the uphole end. Recess  56  is visible as is port  62  both of which are at the 12 o&#39;clock position on the drawing. 
     Important to the invention is solenoid dump valve port  64  which accepts in a sealing relationship, a solenoid actuated normally open dump valve  65  which is commercially available from the Lee Company. A representative illustration of a dump valve as employed in the invention is depicted in FIG.  14 . Cross channel  66  is a fluid connection between port  62  and port  64  and allows the safety valve to close if the dump valve opens due to an interruption of power. Operation of this feature will be discussed more fully hereinafter. The manifold is bolted to the sleeve using preferably three points about 120° apart. At these points  72 , are holes to accept bolts  73  secured to the sleeve preferably by “T” receptacles therein. More specifically, and referring to FIG. 15, the sleeve is machined radially from the outside diameter thereof to form “T” shaped slots of a dimension sufficient too receive a bolt head and part of its shank and secure the bolts against axial movement. The remainder of the shanks of each connection point are threaded into the manifold  54  at the indicated holes  72 . A pair of nuts on each shank are preferably employed to lock the spacing of the manifold from the sleeve. 
     Referring again to FIG. 13, nine more holes are apparent, Five of these are indicted by numeral  74  and are preferably equidistantly spaced on a six-hole pattern. The position of the sixth hole would be located between the pump discharge port recess  56  and the solenoid dump valve port  64 . In lieu of the sixth hole, four holes  76  are provided around the port area. Each of the nine holes are preferably counter sunk as illustrated. Each of the nine holes are intended to receive bolts to secure the manifold to the conventional SCSSV. The four bolts  74  ensure a pressure tight connection in the area defined by the o-ring groove  68 . It should be noted that in reservoir  38  a sleeve  39  is preferably installed to take up space so that the volume of fluid in the reservoir can be reduced. The sleeve is preferably aluminum. The reduction is not necessary but is preferred to reduce cost associated with increased piston sleeve  48  travel from hydraulic fluid thermal expansion. The fluid displacement provided by the large annular piston on the piston sleeve  40  provides for the thermal expansion of the hydraulic safety valve and balances the reservoir pressure to the tubing pressure thus requiring that the pump discharge needs only be the differential necessary to compress the power spring, the pump does not have to overcome the tubing side pressure. The back pressure spring provides a positive fluid reservoir pressure required to move the piston sleeve  38  in the dynamic mode while the safety valve is opening in the case of low (atmospheric) tubing pressure. The load on the back pressure spring is dependent on the static and dynamic frictional characteristics of the large and small dynamic seals  42 ,  52  and the area of the annular piston created between the two. In the preferred embodiment the spring is approximately 280 pounds load for about 25 psi in the reservoir. This positive pressure will also keep wellbore fluids and gases from migrating into the reservoir since the differential pressure is higher in the reservoir. 
     In operation, electronics package  20  delivers a potential to normally open solenoid dump valve  80  to close the same. Dump valve  80  is preferably a solenoid operating pilot valve, commercially available from Lee Company. With dump valve  80  closed, cross channel  66  is closed and will not bleed off pressure from the fluid hone bore  70  of the conventional SCSSV. Thus, pressure generated by pump  48  is transmitted to the SCSSV to open the same. Upon any interruption in power to the dump valve  80 , it returns to its normally open position and dumps the fluid pressure back to the reservoir and the SCSSV closes. Assuming that power remains at dump valve  80 , the valve remains closed indefinitely. Upon a signal from the surface, electronics package  20  directs motor  46  to turn pump  48  and generate increasing pressure within inlet  70 . As pressure increases, the conventional safety valve will open. When a particular degree of openness (usually fully open) of the safety valve is achieved as measured by a pressure sensor in the inlet, a proximity sensor on the flapper valve, a counter on the motor, etc., the motor is directed to stop moving and to a discharge check valve in the manifold at  62  will hold pressure in the system. The SCSSV is closeable by cutting power to dump valve  80  causing it to open and dump the fluid pressure in bore  70 . It should be noted that a significant benefit of the present invention is that the SCSSV will close at any state of opening, immediately upon the dump valve opening. A full stroke is not necessary (i.e. some prior art requires that valve be completely open before closing is possible). 
     In an alternate embodiment of the invention, referring to FIGS. 7-12 the motor  46 , pump  48  and sleeve  39  are replaced by a reciprocating positive displacement solenoid plunger pump  110 . Referring specifically to FIG. 9, the solenoid pump  110  is illustrated in position within the tool as are all of the other components (which were not specifically excluded above) of the foregoing embodiment. These are in the same places and have the same function. This embodiment of the invention merely employs an alternative means for causing fluid pressure to rise in inlet  70 . Changes exist in two components of the device in this embodiment: 1) the compensating piston is preferably constructed of a non-magnetic material to avoid a reduction of the field (employed in the operation of the solenoid) that occurs when a magnetic material is employed as the compensating piston. Inconel is a preferred choice for the substitute material of the compensating piston; and 2) the discharge connector  50 ′ is distinct from discharge connector  50 . This is due to the pump outlet and the function served by the connectors  50 ,  50 ′. In the motor/pump first embodiment, the discharge connector preferably is threaded into pump  48  and serves to physically hold the pump and the motor. In the second embodiment, the discharge connector  50 ′ mounts as in a honed bore  112  and seals therein with o-ring  114  but is not fixedly attached. Rather, in a preferred arrangement for the second embodiment, discharge connector  50 ′ is free to move in the bore  112  and the solenoid pump is fixed to the manifold  54  only by the T-bolts described above. In other respects the two embodiments are identical. 
     The solenoid pump embodiment employs a horseshoe wound solenoid to activate an integral plunger pump. More specifically, the armature of the solenoid is a pie shaped section of a ring. The section is approximately ¼ to ⅓ of the ring and includes sides of the pie section at about 45 degrees. The rest of the ring is wound to create the coils of the electromagnet in a direction parallel to the centerline of the ring. When the solenoid is energized, the gap of the pump closes compressing four springs and is the inlet stroke of the pump. When the coil is not energized, the springs extend to their normal length and the fluid that had been taken up in the inlet stroke of the pump is expelled under pressure. The solenoid pump is manufactured commercially by Sub Tech International (formally known as BEI Technology). 
     In a third embodiment of the invention, referring to FIGS. 16-19, a modified configuration of the invention is disclosed. For clarity, elements that are substantially similar will employ identical names as the foregoing and are distinguished therefrom by distinct numerals. Identical components retain the numerals as introduced hereinabove. It is also important to note that in FIGS. 16-19 the tool is shown in one position above the centerline and a second position below the centerline. 
     Beginning with FIG.  16  and proceeding seriatim, electronics housing  120  is connectable to an uphole string (not shown). Electronics housing  120  supports electronics package  30  within an annular space  22  which preferably is nitrogen filled. The space  22  is defined by an outer surface of housing  120  and by an inner surface of an electronics cover  20 . Sealing of the preferred nitrogen gas is by a seal  14  at the uphole end of cover  20  and a premium thread  28  at the downhole end thereof. A distinguishing feature of this embodiment over the foregoing embodiment is that the premium thread  28  mates back up with the electronics housing  120  whereas in the foregoing embodiments it mated with intermediate sub  24 . Electronics housing  120  further provides conductor conduit  122  which links annular space  22  and therefore electronics package  20  to high pressure connector  124  (preferably a Kemlon connector). 
     The connector  124  is inserted into an intermediate sub  126  and is sealed with preferably two O-rings  128  and  130 . Connector  124  is retained in intermediate sub  126  by connector retainer  132  which is threadedly connected to intermediate sub  126 . Connector retainer  132  further includes an axial bore  134  for passage of conductors (not shown). Preferably two connectors are employed. This can be ascertained by review of FIG.  16 A. 
     Intermediate sub  126  provides a through bore  30  which provides passage for current carrying conductors (not shown) to the motor and pump and other electrical components. Housing  120  is connected to intermediate sub  126  at premium threaded connection  26  and threaded connection  136 . On the downhole end of intermediate sub  126 , it is threaded by connected and sealed to pump housing  36  at premium thread  34 . Seal  140 , preferably spring loaded Teflon seal is commercially available from Greene-Tweed &amp; Company. Seal  140  rides against compensator piston  40  to seal hydraulic fluid chamber  38  while piston  40  works to pressure compensate the chamber  38  as in the foregoing embodiments. A back pressure spring  138  is preferred to assist in manufacture of the invention and keeps the piston urged against the hydraulic fluid in space  38  while the tool is at the surface. 
     Also within space  38 , and bathed by the hydraulic fluid contained therein, is solenoid plunger pump  110  which is identical to that described in the second embodiment hereof. Moreover, the pump operates identically to the foregoing and pumps fluid to manifold  144  through union  142 . Fluid pumped to manifold  144  is subsequently urged into the surface controlled subsurface safety valve components (not shown—conventional) to open the same in a manner known to the art. 
     Since it is desirable as described above that manifold  144  be bathed in hydraulic fluid, piston  40  is sealed downhole of manifold  144  by seal  146  and pump housing  36  is sealed by premium threaded connection  98 . It will be appreciated from the drawing FIG. 18 that pump housing  36  is connected at  98  to RHN sub  148 , which sub is employed in the invention in order to allow fluid to go from a single output to an annular fluid chamber created by RHN sub  148  and cylinder sub  152  to allow hydraulic fluid to go to one or more pistons which are located in cylinder sub  152 . Seal  146  also terminates against RHN sub  148  which in a preferred embodiment includes wiper  150  to maintain piston  40  in a clean condition thus prolonging the life of seal  146 . Finally, cylinder sub  152  (FIG. 19) is attached to RHN sub  148  by premium thread  154 . Cylinder sub  152  functions to allow fluid from the output of the pump to access conventional rod piston(s) (which actuate the SCSSV) connected as its downhole end to an otherwise conventional SCSSV. It will be appreciated that the high pressure hydraulic fluid conduit  156  continues from manifold  144  to the SCSSV (not shown) to supply high pressure hydraulic fluid thereto. 
     Turning now to FIGS. 18A and 18B, the manifold  144  of this embodiment of the invention is illustrated in cross-section as indicated by cross-section lines  18 A— 18 A and  18 B— 18 B in FIG.  18 . Manifold  144  is similar to the foregoing embodiments but in this embodiment is configured to accept electronics designed to provide additional information while maintaining the desired function of the manifold as described hereinabove. 
     Referring directly to FIG. 18A, one will recognize from the foregoing description holes  74  and  76  as well as O-ring groove  68 . New to the view is openings  160 ,  162 ,  164  and  166 . These are positioned to optimize function of the manifold and provide fluid continuity to various structures mounted on the uphole side of manifold  144 . Referring then to FIG. 18B, the uphole side of manifold  144  is illustrated. As one will appreciate, holes  72 ,  74  and  76  are illustrated as have been described hereinbefore. Also illustrated are a piloting solenoid port  64  which is in fluid connection with opening  160  to supply high pressure hydraulic fluid to the SCSSV. Adjacent the solenoid valve port  64  is a port  168  for a transducer such as a BEI EDCLIFF transducer which is commercially available from BEI EDCLIFF. The transducer provides information regarding the pressure of the fluid in the control line which holds open the flapper valve of the conventional SCSSV. Such information is valuable to determine the degree of openness of the flapper. Union port  62  is as in the previous embodiments, and a port  170  for a second transducer having one or more capabilities e.g. differential pressure measurement, pressure measurement, etc. which preferably monitors tubing pressure. The preferred transducer is such as a Sensotec transducer which is commercially available from Sensotec. Port  170  communicates with opening  166  port  62  with opening  164  and port  168  communicates with opening  162 . 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.