Abstract:
Methods and apparatus are disclosed. The problems of damage and failure of solenoid valves in high pressure high temperature environments and the problem of difficult repair of solenoid valves are addressed through reduction of the possibility of damage to the ball seat and/or seals and through a modular design to increase the ease of repair and adjustment in the event repair is needed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application claims priority to the provisional patent application identified by U.S. Ser. No. 61/427,402 titled “HIGH PRESSURE HIGH TEMPERATURE (HPHT) WELL TOOL CONTROL SYSTEM AND METHOD” filed on Dec. 27, 2010, the entire content of which is hereby incorporated by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates generally to methods and apparatus for controlling the operation of downhole well tools from the surface, and particularly to a new and improved downhole tool control system adapted for operation in harsh environments, such as high pressure and high temperature. 
       BACKGROUND 
       [0003]    It has become commercially prudent to perform well service operations, such as formation testing and evaluation, in very deep wells using pressure controlled valve devices such as those taught by Upchurch in U.S. Pat. No. 4,796,699, entitled “Well Tool Control System and Method,” assigned to the assignee of this invention, the disclosure of which is hereby incorporated by reference into the specification of this application. 
         [0004]    In U.S. Pat. No. 4,796,699 (hereinafter referred to as “Upchurch”), a well testing tool is disclosed which is not totally mechanical in nature. The tool includes a microelectronics package and a set of solenoid valves responsive to the microelectronics package for opening or closing a valve disposed in the tool. However, the well testing tool of Upchurch is susceptible to damage in extreme, harsh conditions. 
         [0005]    For instance, debris or wear over time may damage the ball seats in the solenoid valves, causing leakage. Leakage may result in failure of the well testing tool, resulting in expensive and time consuming repair of the solenoid valves. Current solenoid valves require disassembly of the entire apparatus to redress the ball seat and replace multiple seals. Additionally, current solenoid valve seals are typically located both externally to the solenoid valve and internally in the solenoid valve and are difficult to repair and/or replace. Further, the complexity of disassembly and reassembly of the current solenoid valves may lead to misassembly errors. Misassembly errors include not properly aligning the solenoid valve at reassembly, cut or damaged seals, introduction of debris, and other errors well known in the art. These errors can lead to binding, leaking, and failure of the solenoid valve. 
         [0006]    It is therefore desirable to provide a well tool control system and method for performing well service operations capable of withstanding harsh conditions, such as debris, high pressure and high temperature, and with ease of re-assembly in the event of wear or failure. 
       SUMMARY 
       [0007]    Methods and apparatus are disclosed. The problems of damage and failure of solenoid valves in high pressure high temperature environments and the problem of difficult repair of solenoid valves are addressed through reduction of the possibility of damage to the ball seat and/or seals and through a modular design to increase the ease of repair and adjustment in the event repair is needed. 
         [0008]    According to an aspect of the present disclosure, one or more embodiments relate to a solenoid valve used in a well control tool to permit actuation of the well control tool. Other aspects of the present disclosure include certain novel features of the solenoid valve design, including packaging, mounting, and filtering. 
         [0009]    These together with other aspects, features, and advantages of the present disclosure, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. The above aspects and advantages are neither exhaustive nor individually or jointly critical to the spirit or practice of the disclosure. Other aspects, features, and advantages of the present disclosure will become readily apparent to those skilled in the art from the following detailed description in combination with the accompanying drawings. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more implementations described herein and, together with the description, explain these implementations. The drawings are not intended to be drawn to scale, and not every component may be labeled in every drawing. In the drawings: 
           [0011]      FIG. 1  depicts a schematic view of a string of drill stem testing tools positioned in a well being tested. 
           [0012]      FIG. 2  depicts a schematic view of hydraulic components in accordance with one or more embodiments of the present disclosure. 
           [0013]      FIG. 3  depicts a schematic view of an alternative configuration of hydraulic components in accordance with one or more embodiments of the present disclosure. 
           [0014]      FIG. 4  depicts an exemplary solenoid valve as known in prior art. 
           [0015]      FIG. 5  depicts an improved solenoid valve in accordance with one or more embodiments of the present disclosure. 
           [0016]      FIG. 6  is an exploded view of an exemplary solenoid valve in accordance with one or more embodiments of the present disclosure. 
           [0017]      FIG. 7  depicts packaging of an improved solenoid valve in accordance with one or more embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
         [0019]    The mechanisms proposed in this disclosure overcome and/or circumvent the problems described above. The present disclosure describes one or more embodiments related to a solenoid valve used in a well control tool to permit actuation of the well control tool. Other aspects of the present disclosure include certain novel features of the solenoid valve design, including packaging, mounting, and filtering. 
         [0020]    Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. 
         [0021]    As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
         [0022]    In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the inventive concept. This description should be read to include one or more and the singular also includes the plural unless it is obvious that it is meant otherwise. 
         [0023]    Further, use of the term “plurality” is meant to convey “more than one” unless expressly stated to the contrary. 
         [0024]    Finally, as used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
         [0025]    Referring initially to  FIG. 1 , a string of drill stem testing tools is shown suspended in a wellbore  10  on drill pipe or tubing  11 , also known as a pipe string. The testing tools comprise a typical packer  12  that acts to isolate the well interval being tested from the hydrostatic head of fluids standing in the annulus  13  space thereabove, and a main test valve assembly  14  that serves to permit or to prevent the flow of formation fluids from the isolated interval into the pipe string  11 . The main test valve assembly  14  is closed while the tools are being lowered, so that the interior of the tubing provides a low pressure region into which formation fluids can flow. After the packer  12  is set, the test valve assembly  14  is opened for a relatively short flow period of time during which pressure in the well bore is reduced. Then the test valve assembly  14  is closed for a longer flow period of time during which pressure build-up in the shut-in well bore is recorded. Other equipment components such as a jar and a safety joint can be coupled between the test valve assembly  14  and the packer  12 , but are not illustrated in the drawing because they are notoriously well known. A perforated tail pipe  15  is connected to the lower end of the mandrel of the packer  12  to enable fluids in the well bore to enter the tool string, and typical inside and outside pressure recorders  16 ,  17  are provided for the acquisition of pressure data as the test proceeds. A circulating valve  20  is connected in the tool string above the main test valve assembly  14 . 
         [0026]    As depicted schematically in  FIG. 2 , the circulating valve  20 , previously identified in  FIG. 1 , includes an elongated tubular housing  21  having a passage  22 . A valve actuator  23  is slideably mounted in the housing  21 , and includes a mandrel  24  having a central passage  25  and an outwardly directed annular piston  26  that is sealed by a seal ring  28  with respect to a cylinder  27  in the housing  21 . Additional seal rings  29 ,  30  are used to prevent leakage between the cylinder  27  and the passage  22 . The seal rings  29 ,  30  preferably engage on the same diameter so that the mandrel  24  is balanced with respect to fluid pressures within the passage  22 . A coil spring  32  located in the housing below the piston  26  reacts between an upwardly facing surface  33  at the lower end of the cylinder  27  and a downwardly facing surface  34  of the piston  26 . The coil spring  32  provides upward force tending to shift the mandrel  24  upwardly relative to the housing  21 . The annular area  35  in which the coil spring  32  is positioned contains air at atmospheric or other low pressure. 
         [0027]    The cylinder area  36  above the piston  26  is communicated by a port  37  to a hydraulic line  38  through which oil or other hydraulic fluid is supplied under pressure. A sufficient pressure acting on the upper face  40  of the piston  26  will cause the mandrel  24  to shift downward against the resistance afforded by the coil spring  32 , and a release of such pressure will enable the spring to shift the mandrel upward to its initial position. The reciprocating movement of the mandrel  24  is employed, as will be described subsequently, to actuate any one of a number of different types of valve elements which control the flow of fluids either through the passage  22  of the housing  21 , or through one or more side ports through the walls of the housing  21 . 
         [0028]    The source of hydraulic fluid under pressure is a high pressure chamber  42  that is filled with hydraulic oil. The high pressure chamber  42  is pressurized by the hydrostatic pressure of well fluids in the well annulus  13  acting on a floating piston which transmits such pressure to the oil. A line  43  from the high pressure chamber  42  leads to a first solenoid valve  44  which has a spring loaded, normally closed valve element  45  that engages a seat  46 . Another line  47  leads from the seat  46  to a line  48  which communicates with a first pilot valve  50  that functions to control communication between a hydraulic line  51  that connects with the actuator line  38  and a line  52  that also leads from the high pressure chamber  42 . A second solenoid valve  53  which also includes a spring loaded, normally closed valve element  54  engageable with a seat  55  is located in a line  56  that communicates between the lines  47 ,  48  and a dump chamber  57  that initially is empty of liquids, and thus contains air at atmosphere or other low pressure. 
         [0029]    The hydraulic system as shown in  FIG. 2  also includes a third, normally closed solenoid valve  65  located in a line  66  that extends from the high pressure chamber  42  to a line  67  which communicates with the pressure side of a second pilot valve  68 . The pilot valve  68  also includes a shuttle  70  that carries seal rings  71 ,  72  and which is urged toward its closed position by a coil spring  74 , where the shuttle closes an exhaust line  73  that leads to the dump chamber  57 . A fourth, normally closed solenoid valve  76  is located in a line  77  which communicates between the pressure line  67  of the pilot valve  68  and the dump chamber  57 . The solenoid valve  76  includes a spring biased valve element  78  that coacts with a seat  79  to prevent flow toward the dump chamber  57  via the line  77  in the closed position. In like manner, the third solenoid valve  65  includes a spring-loaded, normally closed valve element  80  that coacts with a seat  81  to prevent flow of oil from the high pressure chamber  42  via the line  66  to the pilot input line  67  except when opened, as shown, by electric current supplied to its coil. When the solenoid valve  65  is open, oil under pressure supplied to the input side of the pilot valve  68  causes the shuttle  70  to close off the dump line  73 . Although high pressure also may be present in the line  82  which communicates the outer end of the shuttle  70  with the lines  51  and  38 , the pressures in lines  67  and  82  are equal, whereby the spring  74  maintains the shuttle closed across the line  73 . Although functionally separate pilot valves have been shown, it will be recognized that a single three-way pilot valve could be used. 
         [0030]      FIG. 3  is another schematic depiction of an exemplary operation of solenoid valves in a downhole test tool. The set of solenoid valves  44  and  53  embodied in the well tool are energized by a microcontroller (not shown) also embodied in the well tool, which microcontroller is responsive to an output signal from any type of sensor, such as a pressure transducer embodied in the tool that further responds to changes in downhole pressure created and initiated by an operator at the well surface. It is understood that the sensor may be responsive to other stimuli than downhole pressure. Such microcontrollers and sensor systems are well known in the art and, as such, will not be further explained. 
         [0031]    The solenoid valves  44  and  53 , when energized in a first predetermined manner, open and close a set of pilot valves  50  that permit a hydraulic fluid under pressure, stored in a high pressure chamber  42 , to flow to another section of the tool housing where an axially movable mandrel  70  is positioned. The fluid moves the mandrel  70  from a first position to a second position thereby opening another valve  20  in the tool (for example, a test valve or a reversing valve). When the set of solenoid valves  44  and  53  are energized in a second predetermined manner, the hydraulic fluid, stored in the other section of the tool housing, where the movable mandrel  70  is positioned, is allowed to drain from the housing to a separate dump chamber  57 ; as a result, the mandrel moves from the second position to the first position, thereby closing the other valve  20 . In each case, the solenoid valves  44  and  53  are responsive to an output signal from the microcontroller, which is, in turn, responsive to an output signal from the sensor, which is, in turn, responsive to changes in other input stimuli, such as changes in pressure in the well annulus. The change in input stimuli is created and initiated, each time, by the operator at the well surface. Therefore, an opening or closing of the other valve(s) in the tool is responsive, each time, to a stimulus change signal (such as changes in downhole pressure) transmitted into the borehole by the operator at the well surface.  FIG. 3  depicts a schematic of a well testing tool which includes one well tool control system for controlling the closure state of one valve. 
         [0032]      FIG. 4  illustrates an example of a prior art solenoid valve  100 . The prior art solenoid valve  100  contains two seals,  102  and  104 , external to the prior art solenoid valve  100 , and one seal  106  internal to the prior art solenoid valve  100 . In the prior art, if the prior art solenoid valve  100  is disassembled for repair, all three seals  102 ,  104 , and  106  may require redress. Each seal replacement carries a risk of misassembly that may cause leakage. Further, of these seals, the internal seal  106 , depicted in  FIG. 4  as an O-ring, is deeply inside the prior art solenoid valve  100 . Redressing the internal seal  106  requires dissembling the prior art solenoid valve  100  assembly. 
         [0033]    Additionally, the prior art solenoid valve  100  has no filtered flow path to control debris. Since the prior art solenoid valve  100  uses a seal comprised of the mating of a ball  108  to a metal seat  110 , the sealing quality is very sensitive to debris. Once debris is introduced into the system, the metal seat  110  of the seal may be damaged by even small amounts of the debris. Once the seat  110  is damaged, the ball-to-seat seal is compromised and leakage may occur. Leakage may then result in the ultimate failure of the prior art solenoid valve  100 . If the prior art solenoid valve  100  fails, the tool must be pulled from the well so that the prior art solenoid valve  100  may be replaced or repaired, an expensive and time consuming process. 
         [0034]    To repair the prior art solenoid valve  100  ball-to-seat seal, the prior art solenoid valve  100  is entirely disassembled to reach the metal seat  110 . The metal seat  110  is then repaired or replaced and the prior art solenoid valve  100  is completely reassembled. This reassembly also carries a risk of misalignment, which may cause binding or leakage in the reassembled prior art solenoid valve  100 . 
         [0035]    Additionally, since the metal seat  110  is contained in a component within the prior art solenoid valve  100  assembly, tightly held tolerances of the components are required in order to obtain the ball-to-seat relationship needed for a seal. 
         [0036]    When the prior art solenoid valve  100  is mounted in the well tool, space is needed on the well tool to store the solenoid wire. Then a wire cap is needed to seal off this cavity. Due to limited space on the well tool, traditionally this wire cap used a face seal which tends to leak when conducting surface pressure testing. 
         [0037]      FIG. 5  is an illustration of one embodiment of this disclosure in which a solenoid valve assembly  150  is depicted. The workings of solenoid valves are well known in the art and will not be discussed in depth. 
         [0038]    The solenoid valve assembly  150 , in general, is provided with a solenoid housing  152 , a ground spring  154 , a first end filter  156 , a port filter  158 , a spring  160 , a plunger  162 , an electromagnetic solenoid coil  164 , a ball  166 , a lock nut  168 , a seal member  170 , a seal  172 , a ball seat member  174 , and a ball seat member filter  176 . 
         [0039]    The solenoid housing  152  may have an outer wall  184 , a first end  186 , a second end  188 , and a solenoid housing bore  190 , the solenoid housing bore  190  being generally longitudinal extending along an axis through the first end  186  and the second end  188 . The solenoid housing bore  190  creates an inner wall  192  of the solenoid housing  152 , and the solenoid housing  152  may also have at least one port  194  connecting to the solenoid housing bore  190  through the solenoid housing  152 . 
         [0040]    The ground spring  154  may be disposed around the outer wall  184  of the solenoid housing  152 . In this example, the ground spring  154  is in contact with the outer wall  184  of the solenoid housing  152 , as shown in  FIG. 7 . 
         [0041]    The first end filter  156  may be disposed in the solenoid housing bore  190  at the first end  186  of the solenoid housing  152 . The port filter  158  may be disposed in the port  194 , or outside of the port  194 . The spring  160  may be disposed in the solenoid housing bore  190  between the first end filter  156  and the second end  188  of the solenoid housing  152 . 
         [0042]    The plunger  162  may be disposed in the solenoid housing bore  190  between the spring  160  and the second end  188 . However, the plunger  162  may also be described as between the first end  186  and the second end  188  of the solenoid housing  152 . 
         [0043]    The electromagnetic solenoid coil  164  acts upon the plunger  162 , and may be disposed at least in part around the plunger  162 . The ball  166  is disposed in the solenoid housing bore  190  between the plunger  162  and the second end  188  of the solenoid housing  152 . The ball  166  may be movable within the solenoid housing bore  190  by way of a linkage with the plunger  162 . 
         [0044]    The lock nut  168  may have a lock nut first end  202 , a lock nut second end  204 , and a lock nut bore  206  extending between the lock nut first end  202  and the lock nut second end  204  creating a lock nut inner wall  208 . The lock nut  168  may also have a mechanism for attaching the lock nut inner wall  208 , proximate to the lock nut first end  202 , to the outer wall  184  of the solenoid housing  152 , proximate to the second end  188  of the solenoid housing  152 , such that the lock nut  168  is adjustable along the outer wall  184  of the solenoid housing  152 . In one embodiment, the mechanism can be threads. 
         [0045]    The seal member  170  may have a first end  212 , a seal groove  214  in the first end  212 , a second end  216 , and a seal member bore  218  through the first end  212  and the second end  216  generally aligned longitudinally with the lock nut bore  206  and the solenoid housing bore  190 . The first end  212  of the seal member  170  may be adjacent to the lock nut second end  204  of the lock nut  168 . Additionally, there may be a seal  172  located in the seal groove  214  of the seal member  170 . 
         [0046]    The ball seat member  174  may have a seat surface end  222 , an outer wall  224 , a distal end  226 , and a ball seat member bore  228  through the seat surface end  222  and the distal end  226 . The ball seat member  174  may be positioned within the solenoid housing bore  190  such that the seat surface end  222  faces the ball  166 . Further, there may be at least one of a ball seat member filter  176  positioned within the ball seat member bore  228  proximate to the distal end  226  of the ball seat member  174 . The ball seat member  174  may be removable through the second end  188  of the solenoid housing  152 . 
         [0047]    The electromagnetic solenoid coil  164  acts on the plunger  162  and the plunger  162  acts on the ball  166  within the solenoid housing bore  190  such that the ball  166  contacts the seat surface end  222  of the ball seat member  174  to form a seal. 
         [0048]    In one embodiment, the plunger  162  in the solenoid housing bore  190  may be spring biased in the closed position with spring  160 , affecting the ball  166  such that the ball  166  contacts the seat surface end  222  of the ball seat member  174  creating a seal between the ball  166  and the seat surface end  222  of the ball seat member  174 . When signaled, the electromagnetic solenoid coil  164  may generate an electromagnetic force to move the plunger  162  within the solenoid housing bore  190  affecting the ball  166  away from the seat surface end  222  of the ball seat member  174 . Moving the ball  166  away from the seat surface end  222  allows fluid to flow through the solenoid housing bore  190  or to various ports  194 , such as port  194   a  and port  194   b  in  FIG. 6 , for example. 
         [0049]    In one embodiment, the plunger  162  is comprised of several components acted upon by the spring  160  and the electromagnetic force of the electromagnetic solenoid coil  164 . Additionally, the solenoid housing  152  may consist of one or multiple housing components. 
         [0050]    In one embodiment of the present disclosure, the ball seat member  174  may be designed so as to be attached to the solenoid housing  152  with the lock nut  168  through the lock nut bore  206  and through the seal member bore  218 . With this attachment method the ball seat member  174  may be disassembled from the solenoid housing  152  by disengaging and removing the lock nut  168 , the seal member  170 , and the ball seat member  174 . 
         [0051]    The ball seat member  174  may then be repaired or replaced with an undamaged ball seat member  174 . Also, the single seal  172  located on the seal member  170  may be replaced. Re-assembly of the solenoid valve assembly  150  is comprised of reattachment of the lock nut  168  with the seal member  170 , seal  172 , and ball seat member  174  to the solenoid housing  152 . 
         [0052]    In one embodiment, the ball seat member  174  is provided with one or more ball seat member filters  176  filtering fluid entering the ball seat member bore  228 . Additionally, one or more first end filters  156  are provided for the solenoid housing bore  190 . Further, one or more port filters  158  are provided for the one or more ports  194 , for example port  194   a  and port  194   b  as illustrated in  FIG. 6 , near the ball  166 . The ball seat member filter(s)  176 , first end filter(s)  156 , and port filter(s)  158 , assist in protecting the seat surface end  222  of the ball seat member  174  from debris that may damage the seat surface end  222 . Damage to the seat surface end  222  of the ball seat member  174  may cause leakage and eventual failure of the solenoid valve assembly  150 . The ball seat member filter(s)  176 , first end filter(s)  156 , and port filter(s)  158  may be held in place by retaining rings, or any retaining mechanism as is well known in the art. 
         [0053]      FIG. 6  is an exploded view of one embodiment of the lock nut  168 , seal member  170 , and ball seat member  174  from the solenoid valve assembly  150 . It should be recognized that the lock nut  168 , seal member  170  and ball seat member  174  may be separate components or may be combined in part or in whole combination as a single component. 
         [0054]    In the embodiment illustrated in  FIG. 6 , the lock nut  168  is a cylindrical member attachable to and removable from the solenoid housing  152  of the solenoid valve assembly  150 . The mechanism for attachment between the lock nut  168  and the solenoid housing  152  may be comprised of threads, retaining rings, locking mechanisms, or other attachment mechanisms that are well known in the art. Further, the ball seat member  174  is illustrated as a cylindrical member with a mechanism for attachment of the outer wall  224  of the ball seat member  174  to the inner wall  195  of the solenoid housing  152 . The mechanism of attachment between the outer wall  224  of the ball seat member  174  and the inner wall  192  of the solenoid housing  152  may be comprised of threads, retaining rings, locking mechanisms, or other attachment mechanisms that are well known in the art. 
         [0055]    The adjustable attachment mechanisms of the lock nut  168  and the ball seat member  174  to the solenoid housing  152  allows adjustment of the space between the ball  166  and the ball seat member  174  such that larger tolerances may be used in machining the components of the solenoid valve assembly  150 . This allows the solenoid valve assembly  150  components and features to be machined with less precision than in prior art, where, as illustrated in  FIG. 4 , the metal seat  110  component was assembled completely internally to the housing of the solenoid valve  100  assembly. Larger tolerances are advantageous as a reduction in manufacturing cost and as an aid to easier assembly. 
         [0056]    In one embodiment, at assembly, or reassembly, of the solenoid valve assembly  150 , the ball seat member  174  and the ball  166  are pressed together to deform the seat surface end  222  of the ball seat member  174  with the surface of the ball  166 . This creates a seal fit between the ball  166  and the seat surface end  222  of the ball seat member  174 . In one embodiment, the material used for the seat surface end  222  of the ball seat member  174  may be a material that deforms sufficiently to create a seal fit between the ball  166  and the seat surface end  222  of the ball seat member  174 , but that resists further deformation. In a specific embodiment, this material may be a nickel based corrosion resistant alloy. 
         [0057]      FIG. 7  illustrates one embodiment of the solenoid valve assembly  150  in which the solenoid valve assembly  150  is shown mounted to a downhole well tool housing. The solenoid valve assembly  150  may be provided with a ground spring  154  which is positioned around at least part of the outside of the outer wall  184  of the solenoid housing  152  and on the inside of the well tool housing that receives the solenoid valve assembly  150 . The ground spring  154  provides electrical grounding between the solenoid valve assembly  150  and the well tool housing. This is a contrast to prior art which used a grounding wire for electrical grounding, which required the use of an additional cavity on the well tool housing as well as a wire cap that also required a seal, as discussed previously. The use of the ground spring  154  eliminates the need for the grounding wire, the cavity for the grounding wire, the wire cap, and the wire cap seal, along with the possibility of leakage around the wire cap seal. Additionally, the use of the ground spring  154  provides additional tolerance in the location of the solenoid valve assembly  150 , versus a fixed length grounding wire. The ground spring  154  also centers the solenoid valve assembly  150 . 
       CONCLUSION 
       [0058]    Conventionally, solenoid valve assemblies used in downhole well tools in high temperature and high pressure environments have been subject to failure from misassembly and/or damage by debris. In accordance with the present disclosure, an apparatus and a method are disclosed that overcome these problems. The apparatus and method involve a solenoid valve assembly that is protected from debris, is more easily disassembled and reassembled, has an adjustable fit between the ball and seat, and that has fewer seals, thus reducing the opportunity for misassembly or damage. 
         [0059]    The foregoing description provides illustration and description, but is not intended to be exhaustive or to limit the inventive concepts to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the methodologies set forth in the present disclosure. 
         [0060]    Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one other claim, the disclosure includes each dependent claim in combination with every other claim in the claim set. 
         [0061]    No element, act, or instruction used in the present application should be construed as critical or essential to the invention unless explicitly described as such outside of the preferred embodiment. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.