Patent Publication Number: US-11021931-B1

Title: Sand fallback submersible pump protection apparatus

Description:
BACKGROUND 
     Field of the Invention 
     The present invention relates to a sand fallback tool that provides protection against unwanted damage to or incapacitation of downhole submersible pumps used to recover formation fluids from subsurface geologic formations through artificial lift. The present invention is directed to a sand fallback tool that prevents sand from settling out of fluids standing in a stagnant production string back onto or into a submersible artificial lift pump. Unwanted sand intrusion into the submersible pump can damage or disable the submersible pump and prevent it from being successfully restarted for continued fluid production to the surface. 
     Background of the Related Art 
     Some subsurface geologic formations produce fluids with entrained sand. The sand can cause problems with production equipment. For example, entrained sand will settle from the fluid in which it is entrained upon interruption of a submersible pump used to pump fluids entering a well from fluid-bearing subsurface geologic formations to the surface. This is called sand fallback. The settling sand can settle in an inactive submersible pump and clog or otherwise impair restoration of operation of the pump. 
     Sand fallback generally occurs when electrical current to a submersible pump is interrupted causing sand entrained in the fluid that was flowing up a production string at the time of the interruption to settle. Settling sand can enter and damage and/or obstruct restoration of the operation of the submersible pump rotors upon reactivation of the pump. 
     Some prior art sand fallback tools include movable components that are often connected through linkages or mechanisms one to the others. Such connected linkages and mechanisms may become clogged, obstructed or otherwise incapacitated by settling sand, thereby preventing smooth restoration of submersible pump operation and resumption of fluid production from the well. 
     One prior art sand fallback tool includes a tubular flow divider to divide a chamber within the sand fallback tool into a central passage and an annular passage, and a diverter disposed adjacent to a proximal connection that couples to a production string. The diverter causes sand settling back into the sand fallback tool during interruptions in the operation of the submersible pump to be diverted in the annular passage, thereby leaving the central passage open for restoration of fluid flow upon reactivation of the submersible pump. Settled sand is thereby accumulated and stored in the annular passage upon interruption of operation of the submersible pump coupled to a distal end of the sand fallback tool. 
     Sand fallback tools are generally elongate tools that are coupled to a submersible pump at a distal connector, coupled to the production string at a proximal connector, and positioned within a well in a vertical orientation so that sand settling out of fluid residing in a stagnant production string is prevented from settling into an inactive submersible pump coupled to the distal connector. 
     SUMMARY 
     Embodiments of the sand fallback tool of the present invention are adapted to be coupled to a distal end of a tubular production string and positioned in a well in a vertical orientation. Embodiments of the sand fallback tool include a distal end adapted for being coupled to a proximal end of a submersible pump, also known as an electrical submersible pump (ESP). Embodiments of the sand fall back tool of the present invention prevent settling sand from entering into the proximal end of a submersible pump coupled to the distal end of the sand fallback tool. 
     Some embodiments of the sand fallback tool of the present invention include movable components that are not physically connected to other movable or immovable components of the tool, but are instead dynamically displaceable by fluid flow within a cage, channel or a chamber in which the movable component can move. Some embodiments of the sand fallback tool of the present invention include one or more check valves that open to allow the flow of fluid, with sand entrained therein, through the sand fallback tool and upwardly into a production tubing through which the fluid flows to the surface during operation of a submersible pump. These check valves will later close to prevent unwanted backflow of fluid and unwanted settling of sand into the submersible pump that is coupled to the distal end of the sand fallback tool when the submersible pump may become inactive. 
     Embodiments of the sand fallback tool of the present invention include a proximal end with a threaded proximal connector for threadedly coupling the sand fallback tool to a distal end of a tubular string that can be stepwise extended into an earthen well to position and support the sand fallback tool and a submersible pump coupled thereto, and a distal end with a threaded distal connector for threadedly coupling to a proximal end (discharge end) of a submersible pump. “Coupling,” as that term is used herein, means that the production tubing and the sand fallback tool, or the sand fallback tool and the submersible pump, may be directly coupled, and it also means that other tools may be coupled intermediate the proximal end of the sand fallback tool and the production tubing or between the distal end of the sand fallback tool and the submersible pump without loss of benefit and use of the sand fallback tool. More than one sand fallback tool can be included within the same tool string for enhanced protection against unwanted sand entry into the submersible pump. 
     The distal connector of embodiments of the sand fallback tool has a bore for the upwardly passage of fluids entering the sand fallback tool from the submersible pump coupled to the distal connector. The proximal connector of embodiments of the sand fallback tool has a bore for passage of fluids exiting the sand fallback tool to then enter a production tubing coupled to the proximal connector of the sand fallback tool. Embodiments of the sand fallback tool include a central chamber that is aligned with the proximal connector of the sand fallback tool and that can receive and store settling sand without obstruction or closing of an annular passage that surrounds the central chamber. The annular passage can, when the central passage is obstructed with settled sand, provide a fluid flow passage to bypass the obstructed central passage and allow the submersible pump to be restarted and operated until the settled sand obstruction can be cleared from the central passage. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a cross-sectional elevation view of an embodiment of the sand fallback tool of the present invention. 
         FIG. 2  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 1  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the flow stop member of the check valve therewithin. 
         FIG. 3  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 1 and 2  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 4  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool of the present invention. 
         FIG. 5  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 4  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the flow stop member of the check valve therewithin. 
         FIG. 6  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 4 and 5  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 7  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool of the present invention. 
         FIG. 8  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 7  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the flow stop member of the check valve therewithin. 
         FIG. 9  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 7 and 8  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 10  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool of the present invention. 
         FIG. 11  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 10  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the cage below the central passage and proximal to the distal end of the tool that houses the flow stop member of the check valve therewithin. 
         FIG. 12  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 10 and 11  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 13  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool of the present invention. 
         FIG. 14  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 13  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the flow stop member of the check valve therewithin. 
         FIG. 15  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 13 and 14  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 16  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool of the present invention. 
         FIG. 17  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 16  after interruption of the power supply to the submersible pump (not shown) and after settling sand has settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate on the flow stop member of the check valve therewithin. 
         FIG. 18  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 16 and 17  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
         FIG. 19  is a cross-sectional elevation view of an embodiment of the sand fallback tool of the present invention. 
         FIG. 20  is the cross-sectional elevation view of the embodiment of the sand fallback tool of  FIG. 19  after interruption of the power supply to the submersible pump (not shown) and after settling sand has bridged and then settled from the stagnant fluid in the production tubing (not shown) above the tool through the proximal connector and into the central passage of the tool to accumulate therewithin. 
         FIG. 21  is the cross-sectional elevation view of an embodiment of the sand fallback tool of  FIGS. 19 and 20  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the tool. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the sand fallback tool of the present invention provide a substantial amount of storage and retention space for settled sand so that the settled sand does not enter and possible clog or otherwise disable a submersible pump coupled to the distal end of the sand fallback tool. Embodiments of the sand fallback tool include an unobstructed axial settling path from a proximal connector of the tool downwardly into a central passage of the tool within the tubular flow divider. The advantages of this structure will be apparent from the discussion that follows. 
       FIG. 1  is a cross-sectional elevation view of an embodiment of the sand fallback tool  10  of the present invention. The sand fallback tool  10  of  FIG. 1  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to a string of production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  axially between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into portions by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 1  is supported within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to and through the proximal connector  26 . The two flow passages include a central passage  16  disposed within the flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . The tubular flow divider  14  of the embodiment of the sand fallback tool  10  of  FIG. 1  is supported within the chamber  11  of the outer tubular body  12  from the proximal end  17  of the tubular flow divider  14 , but may in other embodiments be supported from the distal end  15  or from some other location along the tubular flow divider  14 . 
     The embodiment of the sand fallback tool  10  of  FIG. 1  further includes a distal check valve  31  having a cage  30  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25  and a flow stop member  34  movably captured within the cage  30 . The cage  30  of the distal check valve  31  includes a plurality of holes  32  through which fluid entering the chamber  11  through the distal connector  25  flows with the distal check valve  31  in the open position illustrated in  FIG. 1 . The distal check valve  31  of  FIG. 1  further includes a seat  21  disposed within the chamber  11  of the outer tubular body  12 , the seat  21  sized for sealed engagement with the flow stop member  34 .  FIG. 1  illustrates an embodiment of a sand fallback tool  10  having a distal check valve  31  that includes a flow stop member  34  that is spherical in shape, but in other embodiments of the sand fallback tool  10  of the present invention the flow stop member  34  may be an elongate plug with a tapered nose, such as a conical shape, or any other shape that can maintain a proper orientation within the cage  30  and then sealably engage the seat  21  of the distal check valve  31  upon closure to prevent unwanted fluid flow or settling sand to pass from the chamber  11  through the distal connector  25  and into a submersible pump (not shown) coupled to the distal connector  25  during interruptions of operation of the submersible pump. The flow stop member  34  may be of a material for providing to the flow stop member  34  a combination of density and surface friction to fluid flow there around so that the flow stop member  34  sinks to engage the seat  21  upon termination of operation of the submersible pump (not shown) coupled to the distal connector  25  and the flow stop member  34  is displaced upwardly and off of the seat  21  by application of fluid pressure and fluid flow entering the chamber  11  through the distal connector  25  during operation of the submersible pump. 
     The central passage  16  of the tubular flow divider  14  of the embodiment of the sand fallback tool  10  of  FIG. 1  further includes a distal necked portion  52  proximal to the distal end  15  of the tubular flow divider  14  that is smaller in size than an adjacent portion  53  of the central passage  16 . The central passage  16  includes a proximal check valve  51  including the distal necked portion  52  and a proximal flow stop member  54  within the central passage  16 . The proximal check valve  51  is illustrated in  FIG. 1  in the open position to allow fluid flow to pass upwardly through the central passage  16  and around the proximal flow stop member  54  of the proximal check valve  51 . The proximal check valve  51  further includes a seat  55  within the distal necked portion  52  of the central passage  16  of the tubular flow divider  14 , the seat  55  being shaped for sealed engagement with the proximal flow stop member  54  with the proximal check valve  51  in the closed position. As with the distal check valve  31 , the proximal flow stop member  54  engages the seat  55  to prevent fluid and settled sand from flowing from the central passage  16  through the distal end  15  of the tubular flow divider  14 . The embodiment of the sand fallback tool  10  of  FIG. 1  further includes a tubular extension  63  coupled to the proximal connector  26  of the outer tubular body  12  and extending distally into the chamber  11  and into the central passage  16  of the tubular flow divider  14  to dispose a distal end  64  of the tubular extension  63  within the proximal end  17  of the tubular flow divider  14  and within the central passage  16 . The distal end  64  of the tubular extension  63  serves to limit the range of movement of the proximal flow stop member  54  within the central passage  16  when the proximal flow stop member  54  is displaced from the seat  55  by fluid pressure applied to the proximal flow stop member  54  by operation of the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10 . The tubular extension  63  and the tubular flow divider  16  cause fluid flowing upwardly within the annular passage  18  to flow through an “S”-shaped pathway defined by the distal end  64  of the tubular extension  63  and the proximal end  17  of the tubular flow divider  14  into which the distal end  64  is disposed. During operation of the sand fallback tool  10 , fluid moves within the annular passage  18  upwardly towards the proximal end  22  of the outer tubular body  12  to the proximal end  17  of the tubular flow divider  14 , then radially inwardly through the holes  61  adjacent to the proximal end  17  of the tubular flow divider  14 , then downwardly between the tubular extension  63  and the tubular flow divider  14  to the holes  65  within the tubular extension  63 , and then radially inwardly into the tubular extension  63  to commingle with fluid flowing upwardly from the central passage  16  (if any) of the tubular flow divider  14  and then from the sand fallback tool  10  through the proximal connector  26 . The tubular extension  63  extends a bore  26 A of the proximal connector  26  downwardly into the proximal end  17  of the tubular flow divider  14 . This structure substantially prevents settling sand that may enter the sand fallback tool  10  through the proximal connector  26  during interruptions of operation of the submersible pump (not shown), and causes sand to settle within the central passage  16  of the tubular flow divider  14  instead of settling within the annular passage  18 , as will be discussed in more detail in connection with  FIG. 2 . 
       FIG. 2  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 1  after interruption of a power supply to the submersible pump (not shown) that moves fluid upwardly through the sand fallback tool  10  and after an amount of settling sand  57  has settled from a now-stagnant column of produced fluid residing in a string of production tubing (not shown) coupled to the proximal connector  26  and disposed above the sand fallback tool  10 . As described above, the proximal flow stop member  54  of the proximal check valve  51  engages the seat  55  of the proximal check valve  51  upon interruption of the power supply and the distal flow stop member  34  of the distal check valve  31  engages the seat  21  of the distal check valve  31  due to the density of the proximal flow stop member  54  and the distal flow stop member  34  being greater than the density of the fluid produced through the sand fallback tool  10 .  FIG. 2  shows the settled sand  57  that settles downwardly from the production tubing and that enters the sand fallback tool  10  through the proximal connector  26 , then through the tubular extension  63  extending downwardly therefrom, and into the central passage  16  of the tubular flow divider  14  to accumulate within the central passage  16  and atop the proximal flow stop member  54  engaged with the seat  55  of the proximal check valve  51 . There is an unobstructed axial settling path  99  from the proximal connection  26  into the central passage  16  of tubular divider  14  that is supported within the chamber  11  of the outer tubular body  12 . The unobstructed axial settling path  99  permits settling sand  57  to accumulate within the central passage  16  without blocking the annular passage  18 , thereby permitting at least some fluid flow upon restoration of electrical power to the submersible pump that moves fluid upwardly through the sand fallback tool  10 . The fluid flow provided by maintaining a clear annular passage  18  enables well production to be restored without damaging the submersible pump, which can be damaged by operation of the pump without some minimal amount of fluid throughput. 
     As illustrated in  FIG. 2 , the annular passage  18  remains open and unobstructed by settled sand  57  due to the alignment of the central passage  16  of the tubular flow divider  14  with the tubular extension  63  and the distal end  64  of the tubular extension  63  being disposed below the proximal end  17  of the tubular flow divider  14  to create the “S”-shaped flowpath. The sizes of the tubular extension  63  and the central passage  16  into which the tubular extension  63  extends can be selected to provide a desired pressure drop resisting the flow of fluid up the annular passage  18  of the sand fallback tool  10  so that there is a pressure differential from the annular passage  18  into the central passage  16  of the tubular flow divider  14 . In some embodiments of the sand fallback tool  10  of the present invention, such as the one discussed below in relation to  FIGS. 7-9 , this pressure differential provides for leakage of pressurized fluid from the annular passage  18  through one or more apertures in tubular flow divider  14  into the central passage  16  of the tubular flow divider  14  to unsettle and/or fluidize an otherwise stagnant column of settled sand  57  therein. Upon removal of the sand fallback tool  10  from a well to the surface, apertures in the tubular flow divider  14  may also serve to relieve pressurized pockets of gas that may become trapped in the settled sand  57  that accumulates within the central passage  16  of the tubular flow divider  14 . Embodiments of the present invention of the sand fallback tool  10  having one or more apertures in the tubular flow divider  14  are discussed in greater detail below in connection with  FIGS. 7-9 . 
       FIG. 3  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIGS. 1 and 2  after restoration of power to the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10  and resumption of fluid flow upwardly through the sand fallback tool  10 . Upon restoration of the operation of the submersible pump, fluid pressure initially bears against and displaces the flow stop member  34  of the distal check valve  31  from the seat  21  to provide fluid flow from the submersible pump, through the distal connector  25 , through the holes  32  of the cage  30  of the distal check valve  31 , through the annular passage  18 , through the “S”-shaped flow path formed by the tubular extender  63  and the proximal end  17  of the tubular flow divider  14 , through the holes  65  in the tubular extension  63  to exit from the sand fallback tool  10  by way of the proximal connector  26 . As flow through this fluid flow path defined by these structures occurs, the turbulence of the fluid flow causes unsettling and fluidization of the column of settled sand  57  within the central passage  16 . At first, small amounts of the settled sand  57  begin to become entrained in the fluid flow emerging from the annular passage  18  and leaving the sand fallback tool  10  through the proximal connector  26 . As the column lightens, fluid pressure bearing against the flow stop member  54  of the proximal check valve  51  eventually displaces the flow stop body  54  from the seat  55  and fluid begins to flow into the distal end  15  of the tubular flow divider  14 , around the flow stop member  54  and through the column of settled sand  57 , thereby further entraining sand in the fluid flow exiting the sand fallback tool  10  at the proximal connector  26 . 
       FIG. 4  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The alternate embodiment of the sand fallback tool  10  illustrated in  FIGS. 4-6  resembles the embodiment of the sand fallback tool  10  of  FIGS. 1-3  except that instead of using a cylindrical cage  30  to limit the movement of the flow stop member  34  of the distal check valve  31  as shown in  FIGS. 1-3 , the embodiment of the sand fallback tool  10  of  FIGS. 4-6  includes an alternative type of cage that includes a larger portion of the chamber  11  from the seat  21  to a permeable divider  33  such as, for example, a grate having a plurality of holes in it, to limit the range of movement of the flow stop member  34  while allowing fluid to pass there through. The substitution of the permeable divider  33  shown in  FIGS. 4-6  for the conventional cage  30  shown in  FIGS. 1-3  does not impair the benefit provided by embodiments of the sand fallback tool  10  of the present invention. Similarly, the alternate embodiment of the sand fallback tool  10  illustrated in  FIGS. 4-6  resembles the embodiment of the sand fallback tool  10  of  FIGS. 1-3  except that instead of having holes  65  in the tubular extension  63  to permit continuing fluid flow into the tubular extension  63  when the flow stop member  54  of the proximal check valve  51  engages the distal end  64  of the tubular extension  63 , as illustrated in  FIG. 1 , the tubular flow divider  14  of the embodiment of the sand fallback tool  10  of  FIGS. 4-6  includes a permeable divider  58  to limit the movement of the flow stop member  54  of the proximal check valve  51  as shown in  FIGS. 4-6 , thereby making the holes  65  in the tubular extension  63  (as shown in  FIG. 1 ) unnecessary because the flow stop member  54  of the proximal check valve  51  of the embodiment of the sand fallback tool  10  of  FIG. 4  is prevented by the permeable divider  58  from engaging and closing the distal end  64  of the tubular extension  63  to fluid flow. 
     The sand fallback tool  10  of  FIG. 4  further comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into portions by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 4  is supported within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to the proximal connector  26 . The two flow passages include a central passage  16  disposed within the flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . As with the embodiment of  FIGS. 1-3 , the tubular flow divider  14  of the embodiment of the sand fallback tool  10  of  FIG. 4-6  is supported within the chamber  11  of the outer tubular body  12  from the proximal end  17  of the tubular flow divider  14 , but may in other embodiments be supported from the distal end  15  or from some other location along the tubular flow divider  14 . 
     The sand fallback tool  10  of  FIG. 4  further includes a distal check valve  31  having a permeable divider  33  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25  and a flow stop member  34  movably captured below the permeable divider  33 . The permeable divider  33  of the distal check valve  31  may include a plurality of holes or slots therein through which fluid entering the chamber  11  through the distal connector  25  flows with the distal check valve  31  in the open position illustrated in  FIG. 4 . The distal check valve  31  of  FIG. 4  further includes a seat  21  disposed within the chamber  11  of the outer tubular body  12 , the seat  21  sized for sealed engagement with the flow stop member  34  as discussed below in connection with  FIG. 5 .  FIG. 4  illustrates a flow stop member  34  that is spherical in shape, but in other embodiments of the sand fallback tool  10  of the present invention, the flow stop member  34  can be an elongate plug with a tapered nose, a conical shape, or any other shape that can maintain proper orientation within the chamber  11  and then sealably engage the seat  21  of the distal check valve  31  to prevent unwanted fluid flow or sand passage from the central passage  16  through the distal connector  25  and into the submersible pump (not shown) connected thereto during interruptions of operation of the submersible pump. The flow stop member  34  may be of a material for providing to the flow stop member  34  a combination of size, weight and surface friction to be displaced from the seat  21  and to thereby permit fluid flow around the flow stop member  34  and in the upwardly direction through the permeable divider  33  so that the flow stop member  34  drops or settles within the central passage  16  to sealably engage the seat  21  upon termination of operation of the submersible pump (not shown), and the flow stop member  34  is displaced from the seat  21  by fluid pressure and flow of fluid entering the chamber  11  through the distal connector  25  during operation of the submersible pump. 
     The central passage  16  of the tubular flow divider  14  of the sand fallback tool  10  of  FIG. 4  further includes a distal necked portion  52  proximal to the distal end  15  of the tubular flow divider  14  that is smaller in size than an adjacent portion  53  of the central passage  16  distal to the distal end  15  of the tubular flow divider  14 . The central passage  16  proximal to the distal end  15  further includes a proximal check valve  51  including the distal necked portion  52  and a proximal flow stop member  54  movable within the central passage  16 . The proximal check valve  51  further includes a seat  55  within the tubular flow divider  14  at or adjacent to the distal necked portion  52  that is shaped for sealed engagement with the proximal flow stop member  54 . As with the distal check valve  31 , the proximal flow stop member  54  of the proximal check valve  51  sealably engages the seat  55  to prevent fluid and settled sand from flowing downwardly from the central passage  16  through the distal end  15  of the tubular flow divider  14 . The embodiment of the sand fallback tool  10  of  FIG. 4  further includes a permeable divider  58  within the adjacent portion  53  of the central passage  16  to limit the movement of the flow stop member  54  within the central passage  16  during operation of the submersible pump. The sand fallback tool  10  of  FIG. 4  further includes a tubular extension  63  coupled to the proximal connector  26  of the outer tubular body  12  and extending distally into the chamber  11  and into the proximal end  17  of the tubular flow divider  14 . The distal end  64  of the tubular extension  63  is disposed within the central passage  16 . The tubular extension  63  and the tubular flow divider  14  cause fluid flowing within the annular passage  18  to flow through an “S”-shaped pathway disposed at the proximal end  17  of the flow passage divider  14  and along the tubular extension  63  as described above in relation to  FIGS. 1-3 . Upon restoration of the operation of the submersible pump, the flow of fluid within the annular passage  18  during operation of the submersible pump (not shown) coupled to the distal connector  25  flows upwardly through the distal connector  25 , through the annular passage  18  to the proximal end  17  of the tubular flow divider  14 , passes radially inwardly through the holes  61  therein, flows downwardly along the tubular extension  63  and then radially inwardly into the distal end  64  of the tubular extension  63  to mix with fluid flowing from the central passage  16  (if any) and then the fluid exits from the sand fallback tool  10  through the proximal connector  26 . The tubular extension  63  extends the bore  26 A of the proximal connector  26  downwardly into the central passage  16  of the tubular flow divider  14 . This arrangement causes settling sand  57  that may enter the sand fallback tool  10  through the proximal connector  26  to settle within the central passage  16  of the tubular flow divider  14  instead of settling within the annular passage  18 , as will be discussed in more detail in connection with  FIG. 5 . 
       FIG. 5  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 4  after interruption of the power supply to the submersible pump (not shown) and after settling sand  57  has settled from the stagnant fluid in the production tubing (not shown) above the sand fallback tool  10  through the proximal connector  26 , through the tubular extension  63  and into the central passage  16  of the sand fallback tool  10  to accumulate a column  59  of settled sand  57  atop the flow stop member  54  of the proximal check valve  51 , which is shown in the closed position. There is an unobstructed axial settling path  99  from the proximal connection  26  into the central passage  16  of tubular divider  14  that is supported within the chamber  11  of the outer tubular body  12 . It can be seen in  FIG. 5  how the settled sand  57  has settled through the permeable divider  58  (or grate) that limits movement of the flow stop member  54  and onto the seated flow stop member  54  as it sealably engages the seat  55 . The tubular extension  63  of the embodiment of the sand fallback tool  10  of  FIGS. 4-6  does not contain holes  65  as does the embodiment of the sand fallback tool  10  of  FIG. 1-3  because the divider  58  prevents the flow stop member  54  from engaging and obstructing fluid flow into the tubular extension  63 . 
       FIG. 6  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 4 and 5  after restoration of power to the submersible pump (not shown) and resumption of fluid flow upwardly through the sand fallback tool  10 . Pressurized fluid is pumped into the distal connector  25  and displaces the flow stop member  34  from the seat  21  of the distal check valve  31 . Fluid flows upwardly into and through the annular passage  18  that surrounds the tubular flow divider  14 , through the “S”-curve formed by the distal end  64  of the tubular extension  63  extending into the central passage  16  of the tubular flow divider  14 , radially inwardly into the tubular extension  63  and then through the proximal connector  26  to the production tubing (not shown) connected thereto. As fluid flows through this tortuous pathway, the flowing fluid unsettles and disturbs settled sand  57  thereby causing settled sand  57  to become entrained within the fluid flow. As the amount of the accumulated settled sand  57  atop the flow stop member  54  of the proximal check valve  51  becomes more unsettled and disturbed, the fluid pressure on the flow stop member  54  causes it to become displaced from the seat  55  resulting in fluidization of the column  59  of settled sand  57 , which results in further entrainment of the settled sand  57  in the flow of fluid through the sand fallback tool  10 . The design of the sand fallback tool  10  enables the removal of the column  59  of settled sand  57  from the central passage  16  of the tubular flow divider  14  within a relatively short period after restoration of operation of the submersible pump. 
       FIG. 7  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The sand fallback tool  10  of  FIG. 7  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to production tubing (not shown), a distal end  24  having a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into passages by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 7  is supported within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to the proximal connector  26 . The two flow passages include a central passage  16  disposed within the flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . 
     The sand fallback tool  10  of  FIG. 7  further includes a distal check valve  31  having a permeable divider  33  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25  and a flow stop member  34  movably captured below the divider  33 . The divider  33  of the distal check valve  31  may include a plurality of holes or slots through which fluid entering the chamber  11  through the distal connector  25  flows with the distal check valve  31  in the open position illustrated in  FIG. 7 . The distal check valve  31  of  FIG. 7  further includes a seat  21  disposed within the chamber  11  of the outer tubular body  12 , the seat  21  sized for sealed engagement with the flow stop member  34 .  FIG. 7  illustrates a flow stop member  34  that is spherical in shape, but in other embodiments of the sand fallback tool  10  of the present invention, the flow stop member  34  can be an elongate plug with a tapered nose, a conical shape, or any other shape that can maintain proper orientation within the cage  30  and sealably engage the seat  21  of the distal check valve  31  to prevent unwanted fluid flow or sand passage from the distal connector  25  into the submersible pump (not shown) connected thereto during interruptions of operation of the submersible pump. The flow stop member  34  may be of a material for providing to the flow stop member  34  a combination of size, weight and surface friction to fluid flow upwardly through the distal connector  25  and then around the flow stop member  34  when the flow stop member  34  is displaced from the seat  21  and so that the flow stop member  34  later drops to sealably engage the seat  21  upon termination of operation of the submersible pump (not shown), only to be again displaced from the seat  21  by fluid pressure and flow of fluid entering the chamber  11  through the distal connector  25  during resumed operation of the submersible pump. 
     The central passage  16  of the tubular flow divider  14  of the sand fallback tool  10  of  FIG. 7  further includes a distal necked portion  52  that is smaller in size than an adjacent portion  53  of the central passage  16  that is distal to the distal end  15  of the tubular flow divider  14 . The central passage  16  further includes a proximal check valve  51  that is proximal to the distal end  15  and a proximal flow stop member  54  within the central passage  16 . The proximal check valve  51  further includes a seat  55  within the tubular flow divider  14  at the distal necked portion  52  that is shaped for sealed engagement with the proximal flow stop member  54 . The proximal flow stop member  54  of the proximal check valve  51  engages the seat  55  to prevent fluid and settled sand from flowing from the distal end  15  of the central passage  16 . The sand fallback tool  10  of  FIG. 7  further includes a permeable divider  58  within the central passage  16  to limit the movement of the flow stop member  54  within the central passage  16 . The sand fallback tool  10  of  FIG. 7  further includes a tubular extension  63  coupled to the proximal connector  26  of the outer tubular body  12  and extending distally into the central passage  16 . The distal end  64  of the tubular extension  63  is disposed within the central passage  16 . The tubular extension  63  and the tubular flow divider  16  causes fluid flowing upwardly within the annular passage  18  to flow through an “S”-shaped pathway disposed at the proximal end  17  of the flow passage divider  14 . The flow of fluid within the annular passage  18  flows upwardly to the proximal end  17  of the tubular flow divider  14 , then passes radially inwardly through the holes  61  adjacent to the proximal end  17  of the tubular flow divider  14 , then fluid flows downwardly between the tubular extension  63  and the tubular flow divider  14 , then radially inwardly and into the distal end  64  of the tubular extension  63  to mix with fluid flowing from the central passage  16  (if any), and then upwardly from the sand fallback tool  10  through the proximal connector  26 . The tubular extension  63  extends the bore of the proximal connector  26  downwardly into the central passage  16 . This arrangement substantially prevents settling sand that may enter the sand fallback tool  10  through the proximal connector  26  to settle within the central passage  16  instead of settling within the annular passage  18 , as will be discussed in more detail in connection with  FIG. 8 . 
     The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 7  further includes a plurality of apertures  56 . The apertures  56  allow pressurized fluid to flow from the annular passage  18  through the apertures  56  in the tubular flow divider  14  into the central passage  16  upon restoration of operation of the submersible pump, as discussed in connection with  FIG. 9  below. The apertures  56  in the tubular flow divider  14  thereby promote fluidization and unsettling of the column  59  of settled sand  57  accumulated within the central passage  16  as illustrated in  FIG. 8 , and may also provide for the relieving of pressurized pockets of gas that may remain within the column  59  of settled sand  57  after the sand fallback tool  10  is removed from a well. 
       FIG. 8  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 7  after interruption of the power supply to the submersible pump (not shown) and after a column  59  of settled sand  57  has settled from the stagnant fluid in the production tubing (not shown) above the sand fallback tool  10  through the proximal connector  26 , through the tubular extension  63  and into the central passage  16  of the sand fallback tool  10 . The settled sand  57  is shown in  FIG. 8  to have accumulated into a column  59  of settled sand  57  atop the seated flow stop member  54  of the proximal check valve  51 , which is shown in  FIG. 8  in the closed position. There is an unobstructed axial settling path  99  from the proximal connection  26  into the central passage  16  of tubular divider  14  that is supported within the chamber  11  of the outer tubular body  12 . It can be seen in  FIG. 8  how the column  59  of settled sand  57  has settled through the permeable divider  58  that limits movement of the flow stop member  54  and onto the flow stop member  54 . The tubular extension  63  of the embodiment of the sand fallback tool  10  of  FIGS. 7-9  does not contain holes as it does in the embodiment of the sand fallback tool  10  of  FIG. 1-3  because the permeable divider  58  prevents the flow stop member  54  from engaging and obstructing fluid flow into the tubular extension  63 . 
       FIG. 9  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 7 and 8  after restoration of power to the submersible pump (not shown) and resumption of fluid flow upwardly through the sand fallback tool  10 . Pressurized fluid is pumped into the distal connector  25  and displaces the flow stop member  34  from the seat  21  of the distal check valve  31 . Fluid flows upwardly into the annular passage  18 , radially inwardly through the holes  61  in the tubular flow divider  14 , downwardly between the tubular flow divider  14  and the tubular extension  63 , radially inwardly and then into the distal end  64  of the tubular extension  63 , and fluid exits the sand fallback tool  10  through the proximal connector  26  to the production tubing (not shown) connected thereto. As fluid flows through this pathway, the flowing fluid unsettles and disturbs settled sand  57  thereby causing settled sand  57  to become entrained within the fluid flow. As the amount of the accumulated column  59  of settled sand  57  atop the flow stop member  54  of the proximal check valve  51  becomes more unsettled, the fluid pressure bearing on the flow stop member  54  causes it to become displaced from the seat  55  and fluid begins to channel and flow through the column  59  of the settled sand  57 , which results in further entrainment of the settled sand  57  in the flow of fluid through the sand fallback tool  10 . In addition, pressurized fluid within the annular passage  18  flows through apertures  56  in the tubular flow divider  14  into the central passage  16  to further fluidize and unsettle the column  59  of settled sand  57  accumulated within the central passage  16  of the tubular flow divider  14 . The apertures  56  in the tubular flow divider  14  are large enough to allow fluid flow from the annular passage  18  into the central passage  16 , but small enough for the tubular flow divider  14  to provide support for accumulation of a column  59  of settled sand  57  therewithin. It will be understood that sand, like many other materials, can accumulate within a fluid with sufficient cohesion to create a column  59  of settled sand  57  within the central passage  16  of the tubular flow divider  14  without sand escaping the central passage  16  through the apertures  56  to enter the annular passage  18 . 
       FIG. 10  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The sand fallback tool  10  of  FIG. 10  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  therebetween. The chamber  11  within the outer tubular body  12  is divided into flow passages by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  divides the chamber  11  into a central passage  16  within the tubular flow divider  14  and an annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . Holes  61  in the tubular flow divider  14  adjacent to the proximal end  17  allow fluid flow from the annular passage  18  to flow radially inwardly towards the tubular extension  63 , then downwardly between the tubular extension  63  and the proximal end  17  of the tubular flow divider  14 , then radially inwardly to mix with fluid flowing upwardly from the central passage  16 , if any, then to exit the chamber  11  and the apparatus  10  through the tubular extension  63  and the proximal connector  26 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 10  is supported within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two fluid flow passages through which fluid entering the sand fallback tool  10  through the distal connector  25  may flow to the proximal connector  26 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 10  further includes a bypass annulus  19  within the tubular flow divider  14  and in fluid communication through a plurality of bypass apertures  41  with the central passage  16  of the tubular flow divider  14 . The bypass apertures  41  allow fluid to flow into the distal end  15  of the tubular flow divider  14  and to thereby enter the central passage  16 , then to flow through the bypass apertures  41  into the bypass annulus  19 , upwardly within the bypass annulus  19  and then from the bypass annulus  19  through the bypass apertures  41  back into the central passage  16 . The bypass apertures  41  and the bypass annulus  19  thereby provide additional agitation, fluidization, entrainment and removal of a column  59  of settled sand  57  (not shown in  FIG. 10 —see  FIG. 11 ) from the central passage  16  upon resumption of operation of the submersible pump, as illustrated in  FIG. 12 . The embodiment of the sand fallback tool  10  of  FIGS. 10-12  does not include a proximal check valve as does the embodiments of  FIGS. 1-9 . 
       FIG. 11  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 10  after interruption of the power supply to the submersible pump (not shown) and after a column  59  of settled sand  57  has settled from the stagnant fluid in the production tubing (not shown) above the sand fallback tool  10  through the proximal connector  26  and into the central passage  16  of the sand fallback tool  10 , then through the central passage  16  to accumulate atop the cage  30  of the distal check valve  31  below the tubular flow divider  14  and below the central passage  16 . There is an unobstructed axial settling path  99  from the proximal connection  26  into the central passage  16  of tubular divider  14  that is supported within the chamber  11  of the outer tubular body  12 . The distal check valve  31  is proximal to the distal end  24  of the sand fallback tool  10  and includes a cage  30  that limits the range of movement of the flow stop member  34  of the distal check valve  31 . The column  59  of settled sand  57  is shown as filling portions of the chamber  11  of the outer tubular body  12  of the sand fallback tool  10  below the distal end  15  of the tubular flow divider  14  because there is no proximal check valve within the central passage  16  of the tubular flow divider  14  to prevent settled sand  57  from passing through the central passage  16 . Once the level of the settled sand  57  rises to the distal end  15  of the tubular flow divider  14 , the column  59  of settled sand  57  then begins accumulating within the central passage  16  as illustrated in  FIG. 11 . 
       FIG. 12  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 10 and 11  after restoration of power to the submersible pump and resumption of fluid flow upwardly through the sand fallback tool  10 . Pressurized fluid enters the sand fallback tool  10  through the distal connector  25  and, due to fluid pressure and rapid flow, immediately clears the settled sand  57  from the area of the chamber  11  adjacent to the holes  32  of the cage  30  of the distal check valve  31 , and from around and atop the cage  30  of the distal check valve  31  that limits the movement of the flow stop member  34  of the distal check valve  31 . The removed portion of the settled sand  57  is entrained in and removed by fluid flow moving up the annular passage  18 , then radially inwardly through the holes  61  in the tubular flow divider  14 , downwardly between the tubular extension  63  and the tubular flow divider  14 , through the “S”-curve formed by the tubular extension  63  extending into the proximal end  17  of the tubular flow divider  14 , and from the sand fallback tool  10  through the proximal connector  26 . The remaining portion of the settled sand  57  in the central passage  16  will then be removed by pressurized fluid entering the distal end  15  of the tubular flow divider  14  and then flowing through the bypass apertures  41  into the bypass annulus  19 . Fluid within the bypass annulus  19  will re-enter the central passage  16  through the bypass apertures  41  at or near the top of the settled sand  57  to entrain and remove the settled sand  57  from the central passage  16  until the central passage  16  has been cleared, and then simultaneous fluid flow through both the central passage  16  and the annular passage  18  resumes. 
       FIG. 13  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The embodiment of the sand fallback tool  10  of  FIG. 13  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to a string of production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  axially between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into passages by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 13  is supported within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide a portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to the proximal connector  26 . The two flow passages include a central passage  16  disposed within the tubular flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . 
     The sand fallback tool  10  of  FIG. 13  further includes a distal check valve  31  having a cage  30  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25  and a flow stop member  34  movably captured within the cage  30 . The cage  30  of the distal check valve  31  includes a plurality of holes  32  through which fluid entering the chamber  11  through the distal connector  25  flows with the distal check valve  31  in the open position illustrated in  FIG. 13 . The distal check valve  31  of  FIG. 13  further includes a seat  21  disposed within the chamber  11  of the outer tubular body  12 , the seat  21  sized for sealed engagement with the flow stop member  34 .  FIG. 13  illustrates a flow stop member  34  that is spherical in shape, but in other embodiments of the sand fallback tool  10  of the present invention, the flow stop member  34  can be an elongate plug with a tapered nose, a conical shape, or any other shape that can maintain proper orientation and sealably engage the seat  21  of the distal check valve  31  to prevent unwanted fluid flow or sand passage into the submersible pump during interruptions of operation of the submersible pump. The flow stop member  34  may be of a material for providing to the flow stop member  34  a combination of weight and friction to fluid flow there around so that the flow stop member  34  drops within the cage  34  to sealably engage the seat  21  upon termination of operation of the submersible pump (not shown) and is displaced from the seat  21  by fluid pressure and flow of fluid entering the chamber  11  through the distal connector  25  during operation of the submersible pump. 
     The central passage  16  of the tubular flow divider  14  of the sand fallback tool  10  of  FIG. 13  further includes a distal necked portion  52  that is smaller in size than an adjacent portion  53  of the central passage  16  proximal to the distal end  15  of the tubular flow divider  14 . The central passage  16  proximal to the distal end  15  further includes a proximal check valve  51  including the distal necked portion  52  and a proximal flow stop member  54  within the central passage  16 . The proximal check valve  51  further includes a seat  55  within the tubular flow divider  14  adjacent to the distal necked portion  52  that is shaped for sealed engagement with the proximal flow stop member  54 . As with the distal check valve  31 , the proximal flow stop member  54  engages the seat  55  to prevent fluid and settled sand from flowing from the distal end  15  of the central passage  16  during interruptions of operation of the submersible pump (not shown). The sand fallback tool  10  of  FIG. 13  further includes a tubular extension  63  coupled to the proximal connector  26  of the outer tubular body  12  and extending distally into the proximal end  17  of the tubular flow divider  14 . The distal end  64  of the tubular extension  63  is disposed within the central passage  16 . As with the embodiment of the apparatus  10  illustrated in  FIGS. 1-3 , the distal end  64  of the tubular extension  63  serves to limit the range of upwardly movement of the proximal flow stop member  54  when the proximal flow stop member  54  is displaced from the seat  55  by fluid pressure and fluid flow is applied to the proximal flow stop member  54  by operation of the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10 . As with the embodiment of the apparatus  10  illustrated in  FIGS. 1-3 , the tubular extension  63  includes holes  65  that continue to allow fluid to flow into the tubular extension  63  when the flow stop member  54  engages the distal end  64  of the tubular extension  63 . The tubular extension  63  and the tubular flow divider  16  cause fluid flowing upwardly within the annular passage  18  to flow through an “S”-shaped pathway disposed at the proximal end  17  of the flow passage divider  14 . The flow of fluid within the annular passage  18  flows upwardly to the proximal end  17  of the tubular flow divider  14 , then flows radially inwardly towards the tubular extension  63 , then downwardly to the holes  65  within the tubular extension  63  and then radially inwardly through the holes  65  into the tubular extension  63  to mix with fluid flowing from the central passage  16  (if any) and then from the sand fallback tool  10  through the proximal connector  26 . The tubular extension  63  extends the bore of the proximal connector  26  downwardly into the central passage  16 . This arrangement provides an unobstructed axial settling path  99  (see  FIG. 14 ) through which settling sand may settle from the production tubing (not shown) coupled to the proximal connector  26  during periods of interruption of the power supply to a submersible pump (now shown) coupled to the distal connector  25 , and this arrangement causes settling sand that may enter the sand fallback tool  10  through the proximal connector  26  to settle within the central passage  16  instead of settling within the annular passage  18 , as will be discussed in more detail in connection with  FIG. 14 . Fluid that does not flow through the full length of the annular passage  18  passes radially inwardly through channels  69  to enter the central passage  16 , then flows upwardly through the central passage  16  to the holes  65  of the tubular extension  63  and there mixes with the fluid flow emerging from the annular passage  18 , then flowing radially inwardly towards the tubular extension  63 , then downwardly between the tubular extension  63  and the proximal end  17  of the tubular flow divider  14  to the holes  65  (i.e., through the “S”-shaped flow path) to mix with the fluid flowing through the central passage  16  and exiting the sand fallback tool  10  through the tubular extension  63  and the proximal connector  26 . 
       FIG. 14  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 13  after interruption of the power supply to the submersible pump (not shown) and after a column  59  of settled sand  57  has settled from the stagnant column of produced fluid residing in the production tubing (not shown) above the sand fallback tool  10 . As described above in connection with other embodiments, upon interruption of the power supply to the submersible pump, the proximal flow stop member  54  sealably engages the seat  55  of the proximal check valve  51  and the distal flow stop member  34  sealably engages the seat  21  of the distal check valve  31  due to the density of the proximal flow stop member  54  and the distal flow stop member  34  being greater than the density of the fluid produced through the sand fallback tool  10 .  FIG. 14  shows the settled sand  57  that settles downwardly through the unobstructed axial settling path  99  from the production tubing and entering the sand fallback tool  10  through the proximal connector  26 , then through the tubular extension  63  extending downwardly therefrom, and into the central passage  16  to accumulate atop the proximal flow stop member  54  engaged with the seat  55  of the proximal check valve  51 .  FIG. 14  shows that the annular passage  18  remains open and unobstructed by settled sand due to the alignment of the central passage  16  with the tubular extension  63 . The holes  65  in the tubular extension  63  are below the proximal end  17  of the tubular extension  63  to prevent or minimize unwanted settling sand entry into the annular passage  18 . The sizes of the tubular extension  63  and the central passage  16  into which the tubular extension  63  extends can be selected to provide a desired pressure drop in the fluid produced up the annular passage  18  so that there is a pressure differential from the annular passage  18  into the central passage  16 . 
       FIG. 15  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 13 and 14  after restoration of power to the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10  and resumption of fluid flow upwardly through the sand fallback tool  10 . Upon restoration of the operation of the submersible pump, fluid pressure initially bears against and displaces the flow stop member  34  of the distal check valve  31  from the seat  21  to provide fluid flow from the submersible pump, through the distal connector  25 , through the holes  32  of the cage  30  of the distal check valve  31 , through the full length of the annular passage  18 , then radially inwardly towards the tubular extension  63 , then downwardly between the tubular extension  63  and the proximal end  17  of the tubular flow divider  14  to the holes  65  (i.e., through the “S”-curve at the proximal end  17  of the tubular flow divider  14  to exit from the sand fallback tool  10  through the proximal connector  26 . As flow through these structures occurs, the turbulence of the flow causes unsettling and fluidization of at least a top portion of the column  59  of settled sand  57  within the central passage  16 . At first, small amounts of the settled sand begin to leave the column  59  of settled sand  57  in the central passage  16  and become entrained in the fluid flow emerging from the annular passage  18  and leaving the sand fallback tool  10  through the proximal connector  26 . As the column  59  lightens, fluid pressure against the flow stop member  54  of the proximal check valve  51  eventually displaces the flow stop body  54  from the seat  55  and fluid begins to flow radially inwardly through the channels  69 , into the central passage  16 , around the flow stop member  54  and channeling through the column  59  of settled sand  57 , thereby further fluidizing and entraining sand in the fluid flow exiting the sand fallback tool  10  at the proximal connector  26 . 
       FIG. 16  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The embodiment of the sand fallback tool  10  of  FIG. 16  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to a string of production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  axially between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into passages by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 16  is supported from the distal end  15  within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to the proximal connector  26 . The two flow passages include a central passage  16  disposed within the flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . 
     The sand fallback tool  10  of  FIG. 16  further includes a distal check valve  31  having a cage  30  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25  and a flow stop member  34  movably captured within the cage  30 . The cage  30  of the distal check valve  31  includes a plurality of holes  32  through which fluid entering the chamber  11  through the distal connector  25  flows with the distal check valve  31  in the open position illustrated in  FIG. 16 . The distal check valve  31  of  FIG. 16  further includes a seat  21  disposed within the chamber  11  of the outer tubular body  12 , the seat  21  sized for sealed engagement with the flow stop member  34 .  FIG. 16  illustrates a flow stop member  34  that is spherical in shape, but in other embodiments of the sand fallback tool  10  of the present invention, the flow stop member  34  can be an elongate plug with a tapered nose, a conical shape, or any other shape that can maintain proper orientation and sealably engage the seat  21  of the distal check valve  31  to prevent unwanted fluid flow or sand passage into the submersible pump during interruptions of operation of the submersible pump. The flow stop member  34  may be of a material for providing to the flow stop member  34  a combination of weight and friction to fluid flow there around so that the flow stop member  34  drops within the cage  30  to sealably engage the seat  21  upon termination of operation of the submersible pump (not shown) and is displaced from the seat  21  by fluid pressure and flow of fluid entering the chamber  11  through the distal connector  25  during operation of the submersible pump. 
     The central passage  16  of the tubular flow divider  14  of the sand fallback tool  10  of  FIG. 16  further includes a distal necked portion  52  that is smaller in size than an adjacent portion  53  of the central passage  16  that is proximal to the distal end  15  of the tubular flow divider  14 . The central passage  16  proximal to the distal end  15  further includes a proximal check valve  51  including the distal necked portion  52  and a proximal flow stop member  54  within the central passage  16 . The proximal check valve  51  further includes a seat  55  within the tubular flow divider  14  adjacent to the distal necked portion  52  that is shaped for sealed engagement with the proximal flow stop member  54 . As with the distal check valve  31 , the proximal flow stop member  54  engages the seat  55  to prevent fluid and settling sand from flowing from the distal end  15  of the central passage  16  during interruptions of power supply to the submersible pump coupled to the distal connector  25  of the apparatus  10 . The sand fallback tool  10  of  FIG. 16  further includes a resilient funnel member  75  coupled to the proximal end  17  of the tubular flow divider  14 , the funnel member  75  being shaped as an upwardly expanding section of a cone to cause fluid and settling sand entering the outer tubular body  12  through the proximal connector  26  during periods in which the submersible pump (not shown) coupled to the distal connector  25  is not in operation to be guided to and to enter the proximal end  17  of the tubular flow divider  14  and to thereafter move down the central passage  16  towards the distal end  15 . The funnel member  75  is resiliently deformable and may be made of rubber or some other material that can be deformed by application of force and then resiliently restored to its original shape after the forces causing deformation are removed. The permeable divider  58  within the central passage  16  serves to limit the range of upwardly movement of the proximal flow stop member  54  when the proximal flow stop member  54  is displaced from the seat  55  by fluid pressure applied to the proximal flow stop member  54  by operation of the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10 . The flow of fluid entering the sand fallback tool  10  through the distal connector  25  may flow through both the central passage  16  and the annular passage  18 . The flow of fluid within the annular passage  18  flows upwardly to the proximal end  17  of the tubular flow divider  14 , the fluid pressure collapses and displaces the funnel member  75  a sufficient amount to allow the fluid flow within the annular passage  18  to move upwardly beyond the funnel member  75  and to flow radially inwardly to mix with fluid flowing upwardly from the central passage  16  (if any) before exiting the sand fallback tool  10  through the proximal connector  26 . Fluid not flowing the full length of the annular passage  18  will flow upwardly through the central passage  16  within the tubular flow divider  14 . The flow of fluid within the central passage  16  first flows radially inwardly through channels  69  to enter the central passage  16  and then upwardly through the central passage  16  to the proximal connector  26 . This arrangement substantially causes settling sand that may enter the sand fallback tool  10  through the proximal connector  26  during interruption of the power supply to the submersible pump (not shown) to settle within the central passage  16  (instead of settling within the annular passage  18 ), as will be discussed in more detail in connection with  FIG. 17 . 
       FIG. 17  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 16  after interruption of the power supply to the submersible pump (not shown) and after settling sand  57  has settled from the stagnant column of produced fluid residing in the production tubing (not shown) above the sand fallback tool  10 . As described above, the proximal flow stop member  54  engages the seat  55  of the proximal check valve  31  after interruption of the power supply and the distal flow stop member  34  engages the seat  21  of the distal check valve  31  due to the density of the proximal flow stop member  54  and the distal flow stop member  34  being greater than the density of the fluid produced through the sand fallback tool  10 .  FIG. 17  shows the settled sand  57  that settles downwardly from the production tubing and that enters the sand fallback tool  10  through the proximal connector  26 , then is guided by the funnel member  75  extending upwardly from the proximal end  17  of the tubular flow divider  14  into the central passage  16  of the tubular flow divider  14  to accumulate atop the proximal flow stop member  54  engaged with the seat  55  of the proximal check valve  51 . The settling sand  57  settles downwardly through the unobstructed axial settling path  99  into the central passage  16  to accumulate as a column  59  of settled sand  57  atop the seated proximal flow stop member  54 .  FIG. 17  shows that the annular passage  18  remains open and unobstructed by settled sand due to the alignment of the central passage  16  with the unobstructed axial settling path  99  and with the proximal connector  26 , and due to the funnel member  75  being at its widest span due to the absence of fluid flow and fluid pressure in the annular passage  18  that can, when present, deflect the funnel member  75  radially inwardly as illustrated in  FIG. 16 . 
       FIG. 18  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 16 and 17  after restoration of power to the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10  and resumption of fluid flow upwardly through the sand fallback tool  10 . Upon restoration of the operation of the submersible pump, fluid pressure initially bears against and displaces the flow stop member  34  of the distal check valve  31  from the seat  21  to provide fluid flow from the submersible pump, through the distal connector  25 , through the holes  32  of the cage  30  of the distal check valve  31 , through the full length of the annular passage  18 , past the funnel member  75  (now again collapsed in a deformed state by application of fluid pressure) to exit from the sand fallback tool  10  through the proximal connector  26 . As flow through these structures occurs, the turbulence of the flow causes unsettling and fluidization of the column of settled sand  57  (see  FIG. 17 ) within the central passage  16 . At first, small amounts of the settled sand begin to leave the settled sand column in the central passage  16  and become entrained in the fluid flow emerging from the annular passage  18  and leaving the sand fallback tool  10  through the proximal connector  26 . As the column  59  of settled sand  57  lightens, fluid pressure against the flow stop member  54  of the proximal check valve  51  displaces the flow stop body  54  from the seat  55  of the proximal check valve  51  and fluid begins to flow radially inwardly through the channels  69 , into the central passage  16 , around the flow stop member  54  and channels through the column  59  of settled sand  57 , thereby further fluidizing and entraining sand in the fluid flow exiting the sand fallback tool  10  at the proximal connector  26 . 
       FIG. 19  is a cross-sectional elevation view of an alternate embodiment of the sand fallback tool  10  of the present invention. The embodiment of the sand fallback tool  10  of  FIG. 19  comprises an elongate outer tubular body  12  having a proximal end  22  with a proximal connector  26  for coupling the sand fallback tool  10  to a string of production tubing (not shown), a distal end  24  with a distal connector  25  for coupling to a submersible pump (not shown), and a chamber  11  within the outer tubular body  12  axially between the proximal connector  26  and the distal connector  25 . The chamber  11  within the outer tubular body  12  is divided into passages by a tubular flow divider  14  having a distal end  15 , a central passage  16  within the tubular flow divider  14 , and a proximal end  17 . The tubular flow divider  14  of the sand fallback tool  10  of  FIG. 19  is supported from the proximal end  17  within the chamber  11  of the outer tubular body  12  centrally about the axis  13  to divide the portion of the chamber  11  in which the tubular flow divider  14  is supported into two flow passages through which fluid entering the distal connector  25  may flow to the proximal connector  26 . The two flow passages include a central passage  16  disposed within the flow divider  14  and surrounding the axis  13  and the annular passage  18  radially intermediate the tubular flow divider  14  and the outer tubular body  12 . 
     The sand fallback tool  10  of  FIG. 19  does not include a distal check valve. Instead, the embodiment of the sand fallback tool  10  of  FIG. 19  comprises a cage  30  disposed within the chamber  11  of the outer tubular body  12  proximal to the distal connector  25 , the cage  30  being designed to promote bridging of sand settling atop the cage  30 , to obstruct the pathway of settling sand to prevent it from settling through the distal connector  25  and into the submersible pump (not shown). The cage  30  includes a plurality of holes  32  through which fluid entering or exiting the chamber  11  through the distal connector  25  flows. While the lack of a distal check valve (due to the lack of a flow stop member) at the distal connector  25  allows fluid and sand to flow into the sand fallback tool  10  through the unobstructed axial settling path  99  that includes the proximal connector  26 , then into and through the chamber  11  and to exit the sand fallback tool  10  through the distal connector  25 . The settling sand  57  passing through the restriction to flow caused by the distal necked portion  52  of the central passage  16  is subject to bridging, as shown in  FIG. 20 , at the distal necked portion  52  within the central passage  16  of the tubular flow divider  14  and also atop the cage  30 . While the tendency of the sand entrained within the fluid to bridge is influenced by many factors such as, but not limited to, the velocity of the fluid flow, the amount of sand entrained in the fluid flow, the grain size of the sand, and the dimensions of the distal necked portion  52  relative to the diameter of the central passage  16  thereabove, the bridging of the sand promotes sand settling and accumulation within the central passage  16  and, after a column  59  of settled sand  57  accumulates within the central passage  16 , it forces fluid that flows into the sand fallback tool  10  through the proximal connector  26  during interruptions in power supply to the submersible pump to flow through the “S”-curved flow pathway formed by the distal end  64  of the tubular extension  63  extending downwardly into the central passage  16  in order to get through the annular passage  18  to the distal connector  25 . This tortuous pathway causes sand entrained in the fluid that enters the sand fallback tool  10  through the proximal connector  26  to settle within the central passage  16  and accumulate in a column  59  of settled sand  57 , as shown in  FIG. 20  and discussed below, rather than to follow the tortuous flow path of the “S”-curve, thereby leaving the annular passage  18  clear and unobstructed. 
       FIG. 20  is the cross-sectional elevation view of the embodiment of the sand fallback tool  10  of  FIG. 19  after interruption of the power supply to the submersible pump (not shown) and after settling sand  57  has bridged and then settled from the stagnant fluid in the production tubing (not shown) above the sand fallback tool  10  through the proximal connector  26  and into the central passage  16  of the sand fallback tool  10  to accumulate in a column  59  therewithin.  FIG. 20  shows the settled sand  57  that first bridges across the distal necked portion  52  and then continues to settle downwardly from the production tubing (not shown) and entering the sand fallback tool  10  through the proximal connector  26 , then through the tubular extension  63  extending downwardly therefrom, and into the central passage  16  to accumulate therewithin.  FIG. 20  shows that the annular passage  18  remains open and unobstructed by settled sand due to the alignment of the central passage  16  with the tubular extension  63  and the holes  65  in the tubular extension  63  being below the proximal end  17  of the tubular extension  63 . The sizes of the tubular extension  63  and the central passage  16  into which the tubular extension  63  extends can be selected to provide a desired pressure drop in the fluid produced up the annular passage  18  so that there is a pressure differential from the annular passage  18  into the central passage  16 . 
       FIG. 21  is the cross-sectional elevation view of an embodiment of the sand fallback tool  10  of  FIGS. 19 and 20  after restoration of power to the submersible pump (not shown) coupled to the distal connector  25  of the sand fallback tool  10  and resumption of fluid flow upwardly through the sand fallback tool  10 . Upon restoration of the operation of the submersible pump, fluid pressure initially provides for restoration of fluid flow from the submersible pump (not shown), through the distal connector  25 , through the holes  32  of the cage  30 , through the annular passage  18 , radially inwardly through the holes  61  adjacent to the proximal end  17  and in the tubular flow divider  14 , downwardly along the tubular extension  63 , radially inwardly to enter the distal end  64  of the tubular extension  63  and then to exit from the sand fallback tool  10  through the proximal connector  26 . As flow through these structures occurs, the turbulence of the flow causes unsettling and fluidization of the column  59  of settled sand  57  (see  FIG. 20 ) within the central passage  16 . At first, small amounts of the settled sand  57  begin to leave the settled sand  57  column  59  in the central passage  16  and become entrained in the fluid flow emerging from the annular passage  18  and leaving the sand fallback tool  10  through the proximal connector  26 . As the column lightens, fluid pressure against the flow stop member  54  of the proximal check valve  51  displaces the flow stop body  54  from the seat  55  and fluid begins to channel through the column  59  of settled sand  57  and flow around the flow stop member  54 , thereby further entraining sand in the fluid flow exiting the sand fallback tool  10  at the proximal connector  26 . 
     In embodiments of the sand fallback tool  10  of the present invention, the introduction of fluids into the chamber  11  through the distal connector  25  may introduce bubbles upon resumption of operation of the submersible pump coupled to the distal connector  25 . The introduction of bubbles may enhance the agitation, unsettling and disturbing of an accumulated column  59  of settled sand  57  and thereby assist in the gradual removal of the accumulated column  59  of settled sand  57  from the chamber  11  of the sand fallback tool  10 . 
     Components of embodiments of the sand fallback tool  10  of the present invention may vary in size, shape and structure to suit the application. For example, but not by way of limitation, the length, diameter and shape of the tubular flow divider  14 , the tubular extension  63  and/or the distal check valve  31  may vary. Similarly, the number of apertures  56  of the tubular flow divider  14  and/or the apertures  41  providing fluid communication between the central passage  16  and the bypass annulus  19  may vary in size, location, number and distribution. Also, the size, shape and number of holes  61  in the tubular extension  63  and/or the holes  32  of the cage  30  may vary. The relative dimensions of components of the embodiments of the sand fallback tool  10  of the present invention shown in the appended drawings are merely for purposes of illustration and are not to be taken as limiting of the present invention. The size, shape and structure of components of embodiments of the sand fallback tool  10  of the present invention may be varied to optimize performance, durability, maintenance, reconditioning, repair and compatibility with standard tubulars and other tools. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components and/or groups, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention. 
     The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.