Method and apparatus for use in selectively fracing a well

Abstract

An apparatus for selectively fracing a well includes a tubular body having an exterior surface, and an interior surface that defines an interior bore. An annular flow area that has at least one fluid flow port extends radially through the tubular body to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation. An external sealing sleeve selectively covers the annular flow area. There is a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve. The axial movement is resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port.

1 . An apparatus for use in selectively fracing a well, comprising:
 a tubular body having an exterior surface, and an interior surface that defines an interior bore;   an annular flow area having at least one fluid flow port extending radially through the tubular body from the interior surface to the exterior surface to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation;   an external sealing sleeve detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port;   a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port.   
     
     
         2 . The apparatus of  claim 1 , wherein the pressure actuated sleeve shifting mechanism is a fluid cavity formed between the external sealing sleeve and the exterior surface of the tubular body, the fluid cavity being asymmetrical to provide an asymmetrical pressure distribution so that increasing pressure within the fluid cavity tends to cause axial movement of the external sealing sleeve. 
     
     
         3 . The apparatus of  claim 1 , wherein the pressure actuated sleeve shifting mechanism is an inclined plane in fluid pressure communication with at least one fluid flow port. 
     
     
         4 . The apparatus of  claim 1 , wherein the external sleeve has a first end with a first internal diameter that engages a first sealing area on the exterior surface of the tubular body on a first side of the annular flow area and the external sleeve has a second end with a second internal diameter that engages a second sealing area on the exterior surface of the tubular body on a second side of the annular flow area. 
     
     
         5 . The apparatus of  claim 4 , wherein the first sealing area has a first seal groove in which is positioned a first O-ring seal and the second sealing area has a second seal groove in which is positioned a second O-ring seal. 
     
     
         6 . The apparatus of  claim 1 , wherein a locking engagement is provided between the external sealing sleeve and the exterior surface of the tubular body to lock the external sealing sleeve in the open position. 
     
     
         7 . The apparatus of  claim 6 , wherein several resilient fingers are carried by the external sealing sleeve and the exterior surface of the tubular body has an engagement profile that the resilient fingers engage to maintain the external sealing sleeve in the open position. 
     
     
         8 . The apparatus of  claim 1 , wherein the external sealing sleeve is detachably secured to the exterior surface of the tubular body by shear pins. 
     
     
         9 . The apparatus of  claim 8 , wherein one selects the pre-selected pressure threshold at which the external sealing sleeve moves by using a greater number or fewer number of shear pins. 
     
     
         10 . The apparatus of  claim 8 , wherein the exterior surface of the tubular body has a circumferential shear pin groove to accommodate the shear pins. 
     
     
         11 . A method for use in selectively fracing a well, comprising:
 (a) providing a plurality of apparatus, each apparatus comprising:
 a tubular body having an exterior surface, and an interior surface that defines an interior bore; 
 an annular flow area having at least one fluid flow port extending radially through the tubular body from the interior surface to the exterior surface to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation; 
 an external sealing sleeve detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port; 
 a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port; 
   (b) deploying the apparatuses along a production tubing string in a well with packers being positioned between the apparatuses to isolate production areas, the pre-selected pressure threshold for each production area increasing from a toe of the well toward a heel of the well;   (c) selectively shifting an external sealing sleeve to an open position by applying fluid pressure to the pressure actuated sleeve shifting mechanism;   (d) continuing to apply fluid pressure to pump fluids into the earth formation through the apparatus that has had its external sealing sleeve moved to the open position;   (e) preventing additional flow through the apparatus that has had its external sealing sleeve moved to the open position;   (f) repeating steps (c), (d), and (e) to selectively open the external sealing sleeve in apparatus in the production tubing in stages working toward a wellhead of the well from a remote end of the well.   
     
     
         12 . The method of  claim 11 , wherein the pressure actuated sleeve shifting mechanism is a fluid cavity formed between the external sealing sleeve and the exterior surface of the tubular body, the fluid cavity being asymmetrical to provide an asymmetrical pressure distribution so that increasing pressure within the fluid cavity tends to cause axial movement of the external sealing sleeve. 
     
     
         13 . The method of  claim 11 , wherein the pressure actuated sleeve shifting mechanism is an inclined plane in fluid pressure communication with at least one fluid flow port. 
     
     
         14 . The method of  claim 11 , wherein selectively shifting the external sealing sleeve to the open position comprises using an isolation tool inserted into the tubular body, the isolation tool isolating fluid pressure to a desired portion of the interior surface of the tubular body. 
     
     
         15 . The method of  claim 11 , wherein selectively shifting the external sealing sleve to the open position comprises pumping fluids down the production tubing at pressures just sufficient to selectively shift the external sealing sleeve of the apparatus having a lowest shifting pressure to an open position without shifting the external sealing sleeve of others of the apparatus having higher shifting pressures. 
     
     
         16 . The method of  claim 11 , wherein preventing additional flow comprises:
 pumping balls down the production tubing until the balls seat on and close the at least one fluid flow port on the apparatus that has had its external sealing sleeve moved to the open position; and   using fluid pressure to maintain the balls seated on the at least one fluid flow port while other of the external sealing sleeves in the production tubing are selectively moved to the open position.   
     
     
         17 . In combination:
 a production tubing string having a plurality of apparatuses for use in selectively fracing a well and an isolation tool, each apparatus for use in selectively fracing a well comprising:
 a tubular body having an exterior surface, and an interior surface that defines an interior bore; 
 an annular flow area having at least one fluid flow port extending radially through the tubular body from the interior surface to the exterior surface to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation; 
 an external sealing sleeve detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port; and 
 a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port; and 
   an isolation tool at least partially extended into the production tubing string, comprising:
 a tubular body having a fluid input in fluid communication with a fluid output; 
 seals positioned on either side of the fluid output, the seals being adapted to seal against the interior surface of the tubular body such that fluid flowing from the output is isolated to a desired portion of the interior surface of the tubular body. 
   
     
     
         18 . An isolation tool for selectively applying pressure to a pressure actuated opening of an outer tubular body, the isolation tool comprising:
 a tubular body carrying a first sealing element and a second sealing element, the tubular body having a fluid inlet and a fluid outlet, the tubular body being movable within the outer tubular body;   a pressure cavity defined by an outer surface of the tubular body, the inner surface of the outer tubular body, and the first and second sealing elements, the fluid outlet of the tubular body being in fluid communication with the pressure cavity;   the first sealing element and the second sealing element permitting fluid flow into the pressure cavity and sealing against fluid flow out of the pressure cavity.   
     
     
         19 . The isolation tool of  claim 18 , further comprising an equalizing valve that is open when the isolation tool is being run into the outer tubular body and closes upon application of the fluid pressure within the pressure cavity.