Method and tool for directing an annular flow across a well bore interval

Abstract

There is disclosed a method for treating an isolated hydrocarbon interval feedable through a production tubing inside a well bore and forming an annulus therebetween. A perforated cylindrical tool having an expandable annular seal may attach to the production tubing and house a slidable element positionally responsive to an injection velocity of a well fluid. The tool may be lowered to a sealing depth for bracketing the hydrocarbon interval. Injection of the well fluid may drag a narrowing bore of the slidable element downward for expanding the annular seal against the well bore. The well fluid may also be directed from the element bore to the annulus by aligning an element flow port with a corresponding tool passage, a downstream or an upstream flow being selectable by an injection velocity for slidably aligning the corresponding flow ports having different axial locations.

1 . An isolating tool for selectively orienting the flow of a well fluid with respect to a demarcation in an annulus of a well bore, the annulus defined by a production tubing inside the well bore, the tool attachable to a downhole end of the production tubing injecting or receiving the well fluid, the tool comprising:
 a cylindrical tool housing having a top end conductively connectable to the production tubing and a bottom end opposite the top end;   a lower cylindrical element spring-positioned within and slidably sealing its element exterior against an interior wall of the tool housing, the element having an element bore narrowing toward one end and conductive of the well fluid from the production tubing, the spring-positioning and the narrowing bore configured to compress the element toward the narrowing end of the element in proportion to an injection velocity of the well fluid;   a lower expandable annular seal disposable on an exterior wall of the tool housing for restricting annular fluid flow across the demarcation;   a lower compression means linked to the slidable element for expanding the lower seal against the well bore when the injection velocity of the well fluid exceeds a variable lower seal threshold; and   where exceeding the lower seal threshold enables a treatment of a hydrocarbon production interval surrounding the well bore above the demarcation.   
     
     
         2 . The tool of  claim 1 , wherein:
 the variable lower seal threshold is variable by one or more of a preloading of the positioning spring, a spring constant, a bore length, and a degree of bore narrowing.   
     
     
         3 . The tool of  claim 1 , further comprising:
 an element upstream port connecting the bore to the element exterior above the seal, and an annular upstream passage in the housing, the port and the passage slidably alignable for annular upstream flow from the bore when the injection velocity exceeds an upstream flow threshold and the bottom end of the housing is closed.   
     
     
         4 . The tool of  claim 3 , wherein:
 the upstream flow threshold is variable by setting an axial distance between the port and the passage at a zero injection velocity.   
     
     
         5 . The tool of  claim 3 , further comprising:
 an elongation of the annular passage for varying the upstream threshold to occur over a range of injection velocities.   
     
     
         6 . The tool of  claim 1 , further comprising:
 an element downstream port connecting the bore to the element exterior below the seal, and an annular downstream passage in the housing, the port and the passage slidably alignable for annular downstream flow from the bore when the injection velocity falls below a downstream flow threshold, thereby closing off the bottom end at higher velocities.   
     
     
         7 . The tool of  claim 1 , further comprising:
 an upper slidable element spring-positioned within the tool housing and upstream of the lower slidable element, the element configured with a narrowing bore for compression toward its narrowing end in proportion to the injection velocity, an upper compression means linked to the upper element for expanding an upper annular seal against the well bore when the injection velocity exceeds an upper seal threshold, the lower and the upper slidable elements for isolating and pressurizing the production interval through a perforation cluster in the well bore.   
     
     
         8 . The tool of  claim 7 , further comprising:
 an element upstream port connecting the bore of the lower slidable element to the element exterior above the lower seal, and an annular upstream passage in the housing, the upstream port and the upstream passage slidably alignable for an annular upstream flow from the bore when the injection velocity exceeds an upstream flow threshold, and   an element downstream port connecting the bore of the lower slidable element to the element exterior below the lower seal, and an annular downstream passage in the housing, the downstream port and the downstream passage slidably alignable for an annular downstream flow from the bore when the injection velocity falls below a downstream flow threshold.   
     
     
         9 . The tool of  claim 8 , wherein:
 the tool is configured with the upper seal threshold set at a relatively low injection velocity, and also configured with the lower seal threshold, the upstream flow threshold, and the downstream flow threshold set at a relatively high velocity, thereby remotely directing a stimulation of the production interval when operating above the high velocity, and remotely directing a flushing through the tool when operating at intermediate velocities.   
     
     
         10 . The tool of  claim 8 , wherein:
 the tool is configured to set the upper and the lower seal thresholds at a relatively low injection velocity, and configured to set the upstream and the downstream flow thresholds at a relatively high velocity, thereby remotely directing a tubular injection of a middle production interval straddled by the two seals, an annular injection of an upper production interval above the upper seal, and a tubular injection of a lower production interval below the lower seal when operating at an intermediate injection velocity.   
     
     
         11 . The tool of  claim 1 , wherein:
 the lower annular seal is one of a bank of expandable elastic O-rings and a band of shaped rubber, where the lower compression means squeezes the sides of the seal axially.   
     
     
         12 . An isolating tool for selectively orienting the flow of a well fluid with respect to two demarcations bracketing a fracture zone of a well bore, the tool attachable to a lower end of a production tubing injecting or receiving the well fluid, the production tubing inside the well bore defining an annulus, the tool comprising:
 a cylindrical tool housing having a top end conductively connectable to the production tubing and a bottom end opposite the top end;   a lower and an upper cylindrical element slidingly positioned within and near opposite ends of the tool housing, where each of the elements:
 is spring-positioned with an element exterior sealing against an interior wall of the tool housing, 
 includes an element bore narrowing toward one end and conductive of the well fluid from the production tubing, and 
 is configured to compress the element toward the narrowing end in proportion to an injection velocity of the well fluid by adjusting the spring positioning and bore dimensions; 
   a lower and an upper annular seal each disposable on an exterior wall of the tool housing at the lower and the upper demarcations, respectively, for restricting fluid flow across the annulus;   a lower and an upper compression means linked respectively to the lower and the upper slidable elements for expanding the lower seal against the well bore when the injection velocity exceeds a variable lower seal threshold and for expanding the upper seal against the well bore when the injection velocity exceeds an upper seal threshold; and   where an injection velocity exceeding the upper and the lower seal thresholds seals the annulus at both demarcations for treating the fracture zone.   
     
     
         13 . The isolating tool of  claim 12 , wherein:
 the upper and the lower annular seals each further comprise:
 a conical collar disposable around the housing exterior at the respective well bore demarcation and axially sloping outward in a direction of seal compression; 
 a cylindrical flexure sleeve formed of multiple tines ringed at one end to receive pressure from the respective compression means during fluid injection, the multiple tines free floating at the other end for slidable expansion over the conical collar; 
 a rubber overmolding substantially wrapping the flexure sleeve and expandable at the respective demarcation when acted upon by the respective slidable element; and 
   where an injection velocity exceeding the upper and the lower seal thresholds expands the rubber overmoldings to seal the annulus at both demarcations for treating the fracture zone.   
     
     
         14 . The tool of  claim 13 , wherein:
 the sloping surface of the conical collar is oriented to be widest near the bottom end of the housing for enabling an upward tug on the tubing string to release a stuck seal.   
     
     
         15 . The tool of  claim 12 , wherein:
 the element bore of one of the upper and the lower slidable element narrows toward the top end of the housing for compressing the element in a direction opposite to that of the injection velocity.   
     
     
         16 . The tool of  claim 12 , further comprising:
 an axial bypass downstream of the lower annular seal for closing tubular outflow therefrom and for pressurizing the fracture zone, the axial bypass comprising a conical plug closing off the center of a bottom end of the lower slidable element, a drain gating a central portion of the bottom end of the tool housing and sealingly receivable of the conical plug when the injection velocity is greater than a bypass threshold, and one or more plug vents around the central portion for passing well fluids when the axial bypass is open.   
     
     
         17 . The tool of  claim 12 , further comprising:
 an element upstream port connecting the bore of the lower slidable element to the element exterior above the lower seal, and an annular upstream passage in the housing, the upstream port and the upstream passage slidably alignable for an annular upstream flow from the bore when the injection velocity exceeds an upstream flow threshold and the bottom end of the housing is closed.   
     
     
         18 . (canceled) 
     
     
         19 . (canceled) 
     
     
         20 . (canceled)