Abstract:
A downhole tool includes a valve assembly and a shock absorbing assembly. The valve assembly includes a valve spring operatively connected to a valve body. The shock absorbing assembly includes a spring operatively connected to a shock absorbing body having a fluid passage therethrough. The valve body is configured to selectively engage the shock absorbing body to create a fluid tight seal over the fluid passage in a first position, and to allow a fluid flow through the fluid passage in a second position. The repeated movement cycle of the selective engagement between the valve body and the shock absorbing body generates a pressure pulse or a varying pressure differential across the downhole tool. The repeated movement cycle is powered by a fluid flow. The tool may be selectively activated and deactivated.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/280,213, filed on Jan. 19, 2016, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    In the process of drilling a wellbore, frictional forces acting against the drill pipe or other component running through the wellbore limit the maximum length or depth to which the wellbore may be drilled. Conventional methods of drilling achieve lengths of 10,000 to 15,000 feet. 
         [0003]    Prior art solutions include mechanisms for vibrating the drill pipe during drilling in order to convert static frictional forces on the drill pipe to dynamic frictional forces between the drill pipe and the wall of the wellbore. One method of vibrating drill pipe within a wellbore includes using a valve in the drill string to create a pressure pulse in conjunction with a shock sub. The pressure pulse causes the shock sub to stretch and the drill pipe to vibrate axially, which allows the drill pipe to reach greater lengths or depths within the wellbore. Certain prior art pressure pulse generation tools use a separate power section to activate the valve. These tools, however, use elastomers that are sensitive to heat and chemicals in drilling mud. Other prior art tools use poppet valves that move up and down to open and close fluid ports. These poppet valve tools, however, are very complicated and cannot be used with drilling mud containing any kind of solids. Furthermore, conventional vibrating tools and methods provide vibration during the entire duration of drilling, i.e., from beginning of pumping drilling fluid through the drill pipe and vibration tool. The constant vibration places undue wears on the vibration tool resulting in reduce longevity. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    The disclosure provides an embodiment of a downhole tool. The tool may include a valve assembly. The valve assembly may include a valve spring operatively connected to a valve body. The tool may also include a shock absorbing assembly. The shock absorbing assembly may include a spring operatively connected to a shock absorbing body having a fluid passage therethrough. In the tool, the valve body may be configured to selectively engage the shock absorbing body to create a fluid tight seal over the fluid passage in a first position and to allow a fluid flow through the fluid passage of the shock absorbing body in a second position. Also in the tool, the selective engagement of the valve body and the shock absorbing body may generate a varying pressure differential across the downhole tool. 
         [0005]    In an embodiment, the downhole tool may include a dampener operatively connected to the shock absorbing body for controlling a movement speed of the shock absorbing body. The dampener may comprise a first chamber, a second chamber, and an interconnecting conduit. The interconnecting conduit may comprise an annular space or an aperture. 
         [0006]    In another embodiment, the downhole tool may include a stop mechanism for limiting a movement of the valve body. The stop mechanism may comprise a shoulder configured to engage a portion of the valve body. 
         [0007]    In another embodiment, the downhole tool may include a housing. The valve assembly and the shock absorbing assembly may be disposed within the housing. The shock absorbing body may comprise a piston. 
         [0008]    In another embodiment, the downhole tool&#39;s valve body may include a valve stem extending to a valve plunger. The valve plunger may be configured to engage the shock absorbing body to seal the fluid passage in the first position. 
         [0009]    In another embodiment, the downhole tool&#39;s valve spring may be disposed around the valve stem and a stop sleeve may be disposed between the valve spring and the valve stem for limiting the compression of the valve spring. 
         [0010]    In another embodiment, the downhole tool&#39;s valve plunger may include a guide protrusion. The guide protrusion may at least partially be disposed within the fluid passage of the shock absorbing body in the first position. 
         [0011]    The disclosure also provides an embodiment of a method of generating a pressure pulse in a tubular disposed within a wellbore. The method may include the step of providing a downhole tool positioned in line with the tubular. The downhole tool may comprise a spring-loaded valve body and a shock absorbing system. The method may include the step of flowing a fluid through the tubular and into the downhole tool. The method may include the step of generating a pressure pulse with the downhole tool using the flow of the fluid to repeatedly move the valve body from a first position to a second position. The fluid may be prevented from flowing through the fluid passage in the first position, and may be allowed to flow through a fluid passage of the shock absorbing system in the second position. 
         [0012]    The disclosure provides another embodiment of a method of generating a pressure pulse in a tubular disposed within a wellbore. The method may comprise the step of providing a downhole tool positioned in line with the tubular. The downhole tool may comprise a spring-loaded valve body and a mechanical device. The method may include the step of flowing a fluid through the tubular and into the downhole tool. The method may include the step of opening the valve body with a hydraulic energy of the flow of the fluid. The method may include the step of displacing the mechanical device and storing energy in the mechanical device. The method may include the step of using the stored energy to return the mechanical device to its original position and to close the valve body. 
         [0013]    The disclosure provides another embodiment of a method of generating a pressure pulse in a tubular disposed within a wellbore. The method may comprise the step of providing an extended reach tool in a downhole assembly of the tubular. The extended reach tool may comprise: a valve assembly including a valve spring operatively connected to a valve body, and a shock absorbing assembly including a spring operatively connected to a shock absorbing body having a fluid passage therethrough. The valve body may be configured to selectively engage the shock absorbing body to create a fluid tight seal over the fluid passage in a first position and to allow a fluid flow through the fluid passage in a second position. The method may include the step of flowing a fluid through the tubular and into the extended reach tool. The method may include the step of generating a pressure pulse in the tubular with the extended reach tool with a repeated movement cycle of the valve body and the shock absorbing body between the first position and the second position. The flow of the fluid through the extended reach tool may power the repeated movement cycle. 
         [0014]    In another embodiment of the method, each movement cycle includes the step of allowing the flow of the fluid to move the valve body and the shock absorbing body in a first direction while maintaining the fluid tight seal of the first position, thereby compressing the valve spring and compressing the spring associated with the shock absorbing body. Each movement cycle may also include the step of allowing the shock absorbing body to continue moving in the first direction when the valve body stops moving in the first direction to allow the fluid to flow through the fluid passage of the shock absorbing body. Each movement cycle may also include the step of allowing the valve spring to move the valve body in a second direction opposite the first direction, and allowing the spring that is operatively connected to the shock absorbing body to move the shock absorbing body in the second direction. Each movement cycle may also include the step of allowing the valve body and the shock absorbing body to return to the first position. 
         [0015]    In another embodiment, the method may include the step wherein the valve body stops moving in the first direction when the valve spring reaches a force equilibrium between a spring force of the valve spring and hydraulic forces acting on the valve body that are created by a pressure drop over one or more apertures in the valve body. 
         [0016]    In another embodiment the method may include the step wherein the valve body stops moving in the first direction when a stop mechanism is engaged. 
         [0017]    In another embodiment, the method may include the step wherein the extended reach tool further comprises a dampener operatively connected to the shock absorbing body, and wherein the dampener causes the shock absorbing body to move in the second direction at a slower rate than the rate of movement of the valve body in the second direction. 
         [0018]    The disclosure provides an embodiment of a method of drilling a wellbore. The method may comprise the step of providing an extended reach tool in a downhole assembly of the tubular. The extended reach tool may comprise: a valve assembly including a valve spring operatively connected to a valve body, and a shock absorbing assembly including a spring operatively connected to a shock absorbing body having a fluid passage therethrough. The valve body may be configured to selectively engage the shock absorbing body to create a fluid tight seal over the fluid passage in a first position and to allow a fluid flow through the fluid passage in a second position. The extended reach tool may be configured to provide a vibration action in an activated state and to discontinue the vibration action in a deactivated state. The method may include the step of attaching the extended reach tool to a tubular and a drill bit. The method may include the step of lowering the extended reach tool and the tubular into a wellbore. The method may include the step of drilling the wellbore with the drill bit. The method may include the step of providing a first signal to the extended reach tool to place the extended reach tool in the activated state, thereby vibrating the tubular. 
         [0019]    In another embodiment, the method may include the step of wherein providing the first signal includes increasing a flow rate of a drilling fluid through the extended reach tool to exceed a threshold value to place the extended reach tool in the activated state. 
         [0020]    In another embodiment, the method may include the step of wherein providing the first signal includes increasing a rotary speed of the tubular to exceed a threshold value to place the extended reach tool in the activated state. 
         [0021]    In another embodiment, the method may include the step of wherein providing the first signal includes pumping a body through the extended reach tool. The body may cooperate with a receptacle to place the extended reach tool in the activated state. 
         [0022]    In another embodiment, the method may include the step wherein providing the first signal includes pumping an RFID unit through the extended reach tool. A control unit of the extended reach tool may sense the presence of the RFID unit and place the extended reach tool in the activated state. 
         [0023]    In another embodiment, the method may include the step of wherein providing the first signal includes providing a pressure pulse, a hydraulic signal, or an electronic signal to place the extended reach tool in the activated state. 
         [0024]    In another embodiment, the method may include the step of providing a second signal to the extended reach tool to place the extended reach tool in the deactivated state, thereby discontinuing the vibration of the tubular. 
         [0025]    In another embodiment, the method may include the step of wherein providing the first signal includes increasing a flow rate of a drilling fluid through the extended reach tool to exceed a threshold value to place the extended reach tool in the activated state and wherein providing the second signal includes decreasing the flow rate of the drilling fluid through the extended reach tool to below the threshold value to place the extended reach tool in the deactivated state. 
         [0026]    In another embodiment, the method includes the step of wherein providing the first signal includes increasing a rotary speed of the tubular to exceed a threshold value to place the extended reach tool in the activated state and wherein providing the second signal includes decreasing the rotary speed of the tubular to below the threshold value to place the extended reach tool in the deactivated state. 
         [0027]    In another embodiment, the method may include the step of wherein providing the first signal includes pumping a body through the extended reach tool, wherein the body cooperates with a receptacle to place the extended reach tool in the activated state, and wherein providing the second signal includes pumping a second body through the extended reach tool, wherein the second body cooperates with the receptacle to place the extended reach tool in the deactivated state. 
         [0028]    In another embodiment, the method may include the step of wherein providing the first signal includes pumping an RFID unit through the extended reach tool, wherein a control unit of the extended reach tool senses the presence of the RFID unit and places the extended reach tool in the activated state and wherein providing the second signal includes pumping a second RFID unit through the extended reach tool. The control unit of the extended reach tool may sense the presence of the second RFID unit and place the extended reach tool in the deactivated state. 
         [0029]    In another embodiment, the method may include the step of wherein providing the first signal includes providing a pressure pulse, a hydraulic signal, or an electronic signal to place the extended reach tool in the activated state and wherein providing the second signal includes providing a second pressure pulse, a second hydraulic signal, or a second electronic signal to place the extended reach tool in the deactivated state. 
         [0030]    In another embodiment, the method may include the step of wherein the tubular is a drill string or coiled tubing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a schematic view of an extended reach tool including a valve system and a shock absorbing system in a closed position. 
           [0032]      FIG. 2  is a sequential schematic view of the extended reach tool in a partially open position. 
           [0033]      FIG. 3  is a sequential schematic view of the extended reach tool in an open position. 
           [0034]      FIG. 4  is a graph of the fluctuation in a pressure upstream of the extended reach tool (i.e., P 1  in  FIGS. 1-3 ) over time during a movement cycle of the tool. 
           [0035]      FIG. 5  is a schematic view of an alternate extended reach tool including a stop mechanism for limiting the movement of the valve system, with the tool in a closed position. 
           [0036]      FIG. 6  is a sequential schematic view of the alternate extended reach tool in a partially open position. 
           [0037]      FIG. 7  is a sequential schematic view of the alternate extended reach tool in an open position. 
           [0038]      FIG. 8A  is a sequential, cross-sectional view of another alternate extended reach tool with the valve in the closed position. 
           [0039]      FIG. 8B  is a sequential, cross-sectional view of the alternate extended reach tool with the valve stem and piston moving down simultaneously. 
           [0040]      FIG. 8C  is a sequential, cross-sectional view of the alternate extended reach tool with the valve stem contacting the spring stop. 
           [0041]      FIG. 8D  is a sequential, cross-sectional view of the alternate extended reach tool with the piston continuing to move downward and creating a gap. 
           [0042]      FIG. 8E  is a sequential, cross-sectional view of the alternate extended reach tool with the valve stem and piston moving back up into the closed position. 
           [0043]      FIG. 9  is a schematic view of an extended reach tool in use with a drill pipe string in a wellbore. 
           [0044]      FIG. 10  is a schematic view of an extended reach tool in use with coiled tubing in a wellbore. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0045]    With reference to  FIGS. 1-3 , extended reach tool  10  may include valve assembly  12  and shock absorbing assembly  14 . Valve assembly  12  may include valve spring element  16  and valve body  18 . Valve spring element  16  may include a coil spring or any other mechanism for storing energy. Shock absorbing assembly  14  may include shock absorbing spring element  20 , shock absorbing body  22 , and dampener  24 . Shock absorbing spring element  20  may include a coil spring or any other mechanism for storing energy. Dampener  24  may be formed of any mechanism for slowing the movement of shock absorbing body  22 , such as a reservoir or cavities configured to communicate fluid through a restriction plate, nozzle, annulus, or other type of orifice. In one embodiment, tool  10  may be used without dampener  24 . Shock absorbing body  22  may include fluid passage  26  configured to allow fluid flow through shock absorbing body  22 . It should be noted that the illustrated components of tool  10  in  FIGS. 1-3  are symbolic representations and do not limit the structural embodiments of each component. 
         [0046]    P 1  represents a fluid pressure value at a location upstream of tool  10 . P 2  represents a fluid pressure value at a location downstream of tool  10 . The difference between P 1  and P 2  may be referred to as a pressure differential across tool  10 . P 1 , P 2 , and the pressure differential may change over time during the movement cycle of tool  10  as described below. 
         [0047]      FIG. 1  illustrates tool  10  in a closed position with valve body  18  contacting shock absorbing body  22  to create a fluid tight seal that prevents fluid from flowing through fluid passage  26  of shock absorbing body  22 . As a fluid flows in first direction  28  through tool  10  in the closed position, P 1  increases and the pressure differential between P 1  and P 2  increases. Valve body  18  and shock absorbing body  22  are moved in first direction  28 , thereby compressing or expanding valve spring element  16  (depending on the attachment configuration of valve spring element  16 ) and compressing shock absorbing spring element  20 . Valve spring element  16  and shock absorbing spring element  20  store energy as they are compressed or expanded. 
         [0048]    Valve spring element  16  will stop the movement of valve body  18  as illustrated in  FIG. 2  when valve spring element  16  reaches a force equilibrium between its spring forces and hydraulic forces due to a pressure drop over one or more orifices in valve body  18 . At this time, shock absorbing body  22  continues moving in first direction  28 , thereby creating an opening referred to as space  30  between valve body  18  and shock absorbing body  22 . This may be referred to as a partially open position of tool  10 . The fluid flowing through tool  10  may begin to flow through space  30  and fluid passage  26  of shock absorbing body  22 . In this way, P 1  and the pressure differential both begin to decrease. 
         [0049]    Compressed or expanded valve spring element  16  then pushes or pulls valve body  18  in second direction  32  (shown in  FIG. 3 ), expanding space  30  between valve body  18  and shock absorbing body  22 . P 1  and the pressure differential both continue to decrease during this time. 
         [0050]    Once shock absorbing spring element  20  is compressed to its defined compression limit shock absorbing spring element  20  will force shock absorbing body  22  to begin moving in second direction  32  as illustrated in  FIG. 3 . Shock absorbing body  22  will move in second direction  32  at a slower rate than that of valve body  18  due to dampener  24  of shock absorbing system  14 . Once valve spring element  16  and the valve body  18  stop moving in second direction  32 , valve body  18  contacts the shock absorbing body  22  to create the fluid tight seal. In this way, the valve of tool  10  is closed again. Valve body  18  and shock absorbing body  22  then move in first direction  28  again. Dampener  24  allows optimization of the time that space  30  is open and closed for allowing fluid flow through fluid passage  26  of shock absorbing body  22 . Valve spring element  16  functions to allow movement of valve body  18  in first direction  28  and second direction  32 . In one embodiment, valve spring element  16  may be compressed when valve body  18  moves in first direction. In another embodiment, valve spring element  16  may be expanded when valve body  18  moves in first direction. 
         [0051]      FIG. 4  illustrates the variation of P 1  during the movement cycle of tool  10  described above in connection with  FIGS. 1-3 . Point A on the graph illustrates P 1  in  FIG. 1 . P 1  increases when tool  10  is in the closed position. Valve body  18  and shock absorbing body  22  are moving in first direction  28  at Point A. Point B on the graph illustrates P 1  in  FIG. 2 . P 1  is at its maximum when valve body  18  stops moving in first direction  28 . When space  30  is opened, P 1  begins to decrease. Point C on the graph illustrates P 1  in  FIG. 3 . P 1  continues decreasing as long as tool  10  is in the open position. Valve body  18  and shock absorbing body  22  are moving in second direction  32  at Point C. 
         [0052]      FIGS. 5-7  illustrate the movement cycle of extended reach tool  40 , which may include valve assembly  42  having valve spring element  16  and valve body  44 . Tool  40  may include a stop mechanism for stopping the movement of valve body  44  in first direction  28 . In one embodiment, tool  40  may include stop mechanism  46  configured to engage and stop movement of valve body  44 , such as the cooperating shoulder arrangement illustrated in  FIGS. 5-7 . Tool  40  may include any other stop mechanism capable of stopping the movement of valve body  44 , such as a mechanical mechanism, a magnetic mechanism, an electronic mechanism, or a hydraulic mechanism. Extended reach tool  40  including stop mechanism  46  may be useful in applications involving high hydraulic energy, such as use of drilling mud in drilling a wellbore. Extended reach tool  40  may include the same components as tool  10  except as otherwise noted. It should be noted that the illustrated components of tool  40  in  FIGS. 5-7  are symbolic representations and do not limit the structural embodiments of each component. 
         [0053]      FIG. 5  illustrates tool  40  in the closed position with valve body  44  contacting shock absorbing body  22  such that fluid is prevented from flowing through fluid passage  26  of shock absorbing body  22 . As fluid flows in first direction  28  through tool  10  in the closed position, P 1  and the pressure differential between P 1  and P 2  begin to increase. Valve body  44  and shock absorbing body  22  are moved in first direction  28 , thereby compressing or expanding valve spring element  16  (depending on the attachment configuration of valve spring element  16 ) and compressing shock absorbing spring element  20 . Valve spring element  16  and shock absorbing spring element  20  store energy as they are compressed or expanded. 
         [0054]    Referring to  FIG. 6 , valve body  44  stops moving in first direction  28  when it contacts stop mechanism  46 . An opening referred to as space  48  is created when shock absorbing body  22  continues moving in first direction  28  away from valve body  44  when it is stopped. The fluid flowing through tool  40  may begin to flow through space  48  and fluid passage  26  of shock absorbing body  22 . In this way, P 1  and the pressure differential between P 1  and P 2  both begin to decrease. 
         [0055]    Compressed or expanded valve spring element  16  then pushes or pulls valve body  44  in second direction  32  (shown in  FIG. 7 ), expanding space  48 . P 1  and the pressure differential between P 1  and P 2  both continue to decrease during this time. 
         [0056]    Once shock absorbing spring element  20  is compressed to its defined compression limit, spring element  20  forces shock absorbing body  22  to begin moving in second direction  32  as illustrated in  FIG. 7 . Shock absorbing body  22  moves in second direction  32  at a slower rate than that of valve body  44  due to dampener  24 . Once valve spring element  16  reaches its lessened position and valve body  44  stops moving in second direction  32 , shock absorbing body  22  contacts valve body  44  to form the fluid tight seal of the closed position. Thereafter, shock absorbing body  22  and valve body  44  move in first direction  28  again. Dampener  24  allows optimization of the time that space  48  is open and closed for allowing fluid flow through fluid passage  26  of shock absorbing body  22 . 
         [0057]    With reference now to  FIG. 8A , extended reach tool  50  may include valve assembly  52  and shock absorbing assembly  54  disposed within upper housing  56 , middle housing  58 , and lower housing  60 . Valve assembly  52  may include valve stem  62  extending to valve plunger  64 . At its upper end, valve stem  62  may include one or more annular fluid passages  66 . Valve assembly  52  may also include valve spring  68  disposed around valve stem  62 . Upper stop sleeve  70  and lower stop sleeve  72  may be disposed around valve stem  62 , with upper stop sleeve  70  within an upper portion of valve spring  68  and with lower stop sleeve  72  within a lower portion of valve spring  68 . Lower end  74  of upper housing  56  may include central opening  76  and one or more annular fluid passages  78 . Valve stem  62  may extend through central opening  76  of upper housing  56 . Valve plunger  64  may include face  80  and guide protrusion  82 . 
         [0058]    Also with reference to  FIG. 8A , shock absorbing assembly  54  may include piston  84 , spring seat  86 , and shock absorbing spring  88 . Piston  84  may be designed following standard piston and housing guidelines for hydraulic systems. Wear sleeve  90  may be disposed within an upper end of central bore  92  of piston  84 . Spring seat  94  may retain and align a lower end of shock absorbing spring  88  within lower housing  60 . Shock absorbing assembly  54  may also include dampener  96  formed of first cavity  98 , second cavity  100 , and interconnecting annulus  102  between middle housing  58  and piston  84 . Annulus  102  may have a gap thickness in the range of 0.001-0.100 inches. Alternatively, dampener  96  may be formed of an arrangement of orifices, each orifice having a diameter of 0.005-1 inch. 
         [0059]      FIG. 8A  illustrates tool  50  in a closed position in which plunger face  80  of valve plunger  64  contacts and creates a seal with piston face  104 . Guide protrusion  82  of valve plunger  64  may extend into central bore  92  of piston  84 . 
         [0060]    As seen in  FIG. 8B , fluid flow in the central bore of upper housing  56  is diverted through fluid passages  66  of valve stem  62  and fluid passages  78  of lower end  74  of upper housing  56 . The fluid flow may create a pressure differential between upper housing  56  and lower housing  60 . The fluid pressure may act on an upper end of valve stem  62  and piston face  104 , thereby moving valve stem  62  and piston  84  simultaneously downward (i.e., toward lower housing  60 ). Valve spring  68  is compressed as valve stem  62  moves downward, and shock absorbing spring  88  is compressed as piston  84  moves downward. 
         [0061]    With reference to  FIG. 8C , the downward movement of valve stem  62  is stopped when upper stop sleeve  70  contacts lower stop sleeve  72 . In this way, upper and lower stop sleeves  70  and  72  form a stop mechanism for valve stem  62 . Alternatively, the stop mechanism for tool  50  may be any other mechanism for stopping the movement of valve stem  62 . For example, upper housing  56  may include an inner shoulder configured to engage a portion of valve stem  62  to stop the downward movement of valve stem  62 . In yet another alternate embodiment, tool  50  may function without a physical stop mechanism; instead, valve spring  68  may stop the movement of valve stem  62  when valve spring  68  reaches a force equilibrium between the spring force of valve spring  68  and the hydraulic forces caused by the differential pressure across the area of seal face  80  of valve stem  62 . 
         [0062]    As seen in  FIG. 8D , when valve stem  62  stops moving downward, piston  84  continues moving downward thereby creating an opening between face  80  of valve plunger  64  and piston face  104 . Fluid may flow through this opening and through central bore  92  of piston  84  such that the pressure differential between upper housing  56  and lower housing  60  begins to decrease. 
         [0063]    Referring to  FIG. 8E , as the pressure in upper housing  56  decreases, valve stem  62  begins to move upward due to the spring force of the compressed valve spring  68 . When the downward movement of piston  84  compresses shock absorbing spring  88  to its defined compression limit, shock absorbing spring  88  moves piston  84  in an upward direction. Dampener  96  slows the upward movement of piston  84  by requiring spring seat  86  to force fluid contained in second cavity  100  through annulus  102  into first cavity  98  in order for piston  84  to move upward. The slower upward movement of piston  84  (relative to the upward movement of valve plunger  64 ) lengthens the time that the gap between valve plunger  64  and piston face  104  is open to fluid flow. In other words, dampener  96  reduces the frequency of the movement of piston  84  and the frequency of the pressure differential cycle. 
         [0064]    Thereafter, valve plunger  64  and piston  84  return to the closed position as shown in  FIG. 8A  to create the fluid tight seal. When valve plunger  64  contacts piston face  104 , guide protrusion  82  may engage central bore  92  of piston  84  to align valve plunger  64  to piston  84 . 
         [0065]    The movement cycle described above may be repeated to create a pressure pulse. A drill string above the extended reach tool expands when P 1  or the pressure in upper housing  56  increases, and contracts when P 1  or the pressure in upper housing  56  decreases. The dampener  96  of the extended reach tool controls the frequency of the pressure pulse. For example, the frequency of the pressure pulse may be in the range of 2-30 Hz. 
         [0066]      FIG. 9  illustrates extended reach tool  110  installed on drill string  113  positioned within wellbore  112 . Extended reach tool  110  may be disposed between drill pipe segments  114  and  116  of drill string  113 , and above measurement-while-drilling component  118 , drilling motor  120 , and drill bit  122 . Fluid pumped through the drill string causes extended reach tool  110  to create a pressure pulse in the drill pipe segments of drill string  113 . The pressure pulse, in connection with a shock sub placed above the extended reach tool, reduces frictional forces between the drill pipe segments and wellbore  102 , which allows drill bit  122  to drill wellbore  112  to a greater length than achieved with prior art devices. Extended reach tool  110  may function as tool  10 , tool  40 , or tool  50 . 
         [0067]      FIG. 10  illustrates extended reach tool  130  installed on coiled tubing line  132  positioned within wellbore  134 . Extended reach tool  130  may be disposed below motor head assembly  136  and above drilling motor  138  and mill  140 . Fluid pumped through coiled tubing line  132  causes extended reach tool  130  to create a pressure pulse in coiled tubing line  132 . The pressure pulse stretches and reduces the length of the coil tubing line  132  thus reducing frictional forces and potential spiraling or helical buckling associated with using coiled tubing to reach a greater distance within wellbore  134 . Extended reach tool  130  may function as tool  10 , tool  40 , or tool  50 . 
         [0068]    The arrangement of springs and openings in the extended reach tool described herein may be configured to generate an oscillating pressure pulse or a fluctuating differential pressure. The tool may achieve a pressure pulse with a lower frequency even with higher fluid flow rates due to the dampener of the shock absorbing assembly. The frequency of the pressure pulse generated by the extended reach tool is therefore less dependent on the fluid flow rate due to the dampener. In other words, the dampener can offset the effect of the flow rate fluctuation on the frequency of the pressure pulse by dampening the frequency of the pressure pulse. For example, the pressure pulse of the tool may be in the range of 2-30 Hz. 
         [0069]    The disclosed extended reach tool is more efficient than prior art tools for generating pressure pulses with valves. The tool may not include any elastomers or seals. The extended reach tool may be designed to accommodate fluid flow in the form of drilling fluid or any other liquid or gas. 
         [0070]    The extended reach tool described herein may be configured to be selectively activated downhole. For example, the extended reach tool may be configured to be attached to a drill string or a coiled tubing string, which is run into a wellbore with a drilling motor and a drill bit. A drilling fluid may be pumped through the drill string or coiled tubing string to cause the drill bit to further drill the wellbore. When frictional forces prevent the drill bit from progressing further, a first signal may be sent to the extended reach tool. The first signal may activate the extended reach tool, thereby causing the extended reach tool to vibrate the drill string or coiled tubing string. The vibration may reduce frictional forces and allow the drill bit to progress further, i.e., to drill the wellbore further. The vibrational action may be needed when drilling a lateral or horizontal bore. When vibration is no longer needed, a second signal may be sent to the extended reach tool. The second signal may deactivate the extended reach tool, thereby causing the extended reach tool to cease vibration of the drill string or coiled tubing string. 
         [0071]    With reference to  FIG. 9 , extended reach tool  110  may be configured to be selectively activated. Extended reach tool  110  may be attached to drill string  113  positioned within wellbore  112 . Selectively activated extended reach tool  110  may be disposed between drill pipe segments  114  and  116 , and above measurement-while-drilling component  118 , drilling motor  120 , and drill bit  122 . Drilling fluid pumped through drill string  113  may cause drilling motor  120  and drill bit  122  to drill further into wellbore  112 . When frictional forces prevent or slow the movement of drill bit  122 , a first signal may be sent to selectively activated extended reach tool  110 . The first signal may activate selectively activated extended reach tool  110  such that it vibrates drill string  113  and the bottom hole assembly made up of the measurement-while-drilling component  118 , drilling motor  120 , and drill bit  122 , to reduce the frictional forces, and to allow drill bit  122  to drill further into wellbore  113 . If vibration of drill string  113  is no longer needed, a second signal may be sent to deactivate selectively activated extended reach tool  110 . 
         [0072]    With reference to  FIG. 10 , selectively activated extended reach tool  130  may be attached to coiled tubing line  132  positioned within wellbore  134 . Selectively activated extended reach tool  130  may be disposed below motor head assembly  136  and above drilling motor  138  and mill  140 . Drilling fluid pumped through coiled tubing line  132  and drilling motor  138  may cause drill bit  140  to drill further into wellbore  134 . When frictional forces prevent or slow the movement of drill bit  140 , a first signal may be sent to selectively activated extended reach tool  130 . The first signal may activate selectively activated extended reach tool  130  such that it vibrates coiled tubing line  132  and the bottom hole assembly made up of the motor head assembly  136 , the drilling motor  138  and the mill  140 , to reduce the frictional forces, and to allow mill  140  to drill further into wellbore  134 . If vibration of coiled tubing line  132  is no longer needed, a second signal may be sent to deactivate selectively activated extended reach tool  130 . 
         [0073]    The first signal and the second signal may be provided by any method of remotely activating a tool. In one embodiment, the signals may be provided by increasing or decreasing the flow rate of the drilling fluid above or below a threshold value. For example, a 2⅞ inch diameter selectively activated extended reach tool may have a threshold value of about 1 barrel per minute (bpm). The first signal may be provided by increasing the flow rate of drilling fluid through the selectively activated extended reach tool to any value over 1 bpm (e.g., 3-4 bpm). The second signal may be provided by decreasing the flow rate of drilling fluid through the selectively activated extended reach tool to any value below 1 bpm (e.g., 0.5-0.8 bpm). Alternatively, the signals may be provided by increasing or decreasing the rotary speed of the drill string above or below a threshold value. 
         [0074]    In another embodiment, the signals may be provided by pumping a body (e.g., a ball, plug, or other component) with the drilling fluid. The body may be configured to cooperate with a receptacle in the selectively activated extended reach tool. Pumping a first body through the drill string or coiled tubing string and into the receptacle may activate the selectively activated extended reach tool to vibrate the drill string or coiled tubing string, and dropping a second body into the receptacle may deactivate the selectively activated extended reach tool. 
         [0075]    In yet another embodiment, the selectively activated extended reach tool may include a control unit having a sensor, a battery, a processor, a CPU, and any other components necessary to sense the presence of signal units (e.g., RFID units) in the drilling fluid. The first signal and the second signal may be provided by pumping a signal unit with the drilling fluid. The control unit of the selectively activated extended reach tool may sense the presence of the signal units in the drilling mud, and may then activate the selectively activated extended reach tool to vibrate the drill string or coiled tubing string. The control unit may deactivate the selectively activated extended reach tool if it subsequently senses the presence of other signal units in the drilling mud. 
         [0076]    Alternatively, the signals may be provided by a pressure pulse or pressure pulse sequence. In other embodiments, the signals may be provided by a hydraulic or electronic signal or a sequence of hydraulic or electronic signals that activate and deactivate the selectively activated extended reach tool. 
         [0077]    While preferred embodiments of the present invention have been described, it is to be understood that the embodiments are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalents, many variations and modifications naturally occurring to those skilled in the art from a review hereof.