Method and apparatus for hydraulic fracturing

Abstract

A method of treating a consolidated formation having a wellbore therein. Tubing including a stress relieving tool is provided in the wellbore. An interval in the wellbore wherein the stress relieving tool is located is isolated. The stress relieving tool is actuated to apply mechanical force radially to an uncased inner diameter surface of the wellbore for providing a reduced stress zone of the formation. Fluid pressure is increased in the wellbore to fracture the formation within the reduced stress zone.

What is claimed is: 
     
         1 . A method of treating a consolidated formation having a wellbore therein, the method comprising:
 providing tubing in the wellbore, the tubing comprising a stress relieving tool;   isolating an interval in the wellbore wherein the stress relieving tool is within the interval;   actuating the stress relieving tool to apply mechanical force radially to an uncased surface of the wellbore, thereby non-sealingly engaging the surface for providing a reduced stress zone of the formation; and   increasing fluid pressure in the wellbore to a fracturing pressure to fracture the formation within the reduced stress zone.   
     
     
         2 . The method of  claim 1 , the tubing further comprising a pair of packers, the stress relieving tool located between the pair of packers, and wherein isolating the interval comprises activating the packers for sealingly engaging the surface. 
     
     
         3 . The method of  claim 1  wherein actuating the stress relieving tool comprises flowing fluid into the stress relieving tool at a selected pressure. 
     
     
         4 . The method of  claim 3  wherein the fluid comprises a fracturing fluid. 
     
     
         5 . The method of  claim 4  wherein the selected pressure is a lower pressure than the fracturing pressure. 
     
     
         6 . The method of  claim 3  wherein the fluid comprises a gas. 
     
     
         7 . The method of  claim 1  further comprising producing hydrocarbons from the formation through the tubing following fracturing of the formation. 
     
     
         8 . A method of treating a consolidated formation having a wellbore therein, the method comprising:
 providing tubing in the wellbore, the tubing comprising a pair of packers and a stress relieving tool, the stress relieving tool located between the packers;   activating the packers to apply a first mechanical force radially to an uncased surface of the wellbore to sealingly engage the surface and isolate an interval of the wellbore;   actuating the stress relieving tool to apply a second mechanical force radially to the surface, wherein the second mechanical force is greater than the first mechanical force, for providing a reduced stress zone of the formation; and   increasing fluid pressure in the interval to fracture the formation within the reduced stress zone.   
     
     
         9 . The method of  claim 8  wherein engaging the surface at the second force comprises non-sealingly engaging the surface. 
     
     
         10 . The method of  claim 8  wherein actuating the stress relieving tool comprises flowing fluid into the stress relieving tool at a selected pressure. 
     
     
         11 . The method of  claim 10  wherein the fluid comprises a fracturing fluid. 
     
     
         12 . The method of  claim 11  wherein the selected pressure is a lower pressure than the fracturing pressure. 
     
     
         13 . The method of  claim 10  wherein the fluid comprises a gas. 
     
     
         14 . The method of  claim 8 , further comprising producing hydrocarbons from the formation through the tubing following fracturing of the formation. 
     
     
         15 . A stress relieving tool comprising:
 an elongate tubular having a channel therethrough;   a first actuator sleeve positioned on the tubular, the first actuator sleeve axially movable along the tubular and in fluid communication with the channel for advancing the first actuator sleeve along the tubular in a first direction in response to fluid pressure in the channel;   a first tapered sleeve of decreasing outer diameter in the first direction positioned on the tubular in series with the first actuator sleeve and axially movable along the tubular;   a second tapered sleeve of increasing outer diameter in the first direction positioned on the tubular in series with the first tapered sleeve; and   a c-ring positioned on the tubular between the first and second tapered sleeves;   wherein:
 an inner diameter of the c-ring is equal to an outer diameter at a first portion of the first tapered sleeve, and at a second portion of the second tapered sleeve; 
 the first tapered sleeve is advanced in the first direction by the first actuator sleeve when the first actuator sleeve is advanced in the first direction; and 
 the c-ring is urged radially outward when the first tapered sleeve is advanced underneath the c-ring. 
   
     
     
         16 . The stress relieving tool of  claim 15  further comprising a protrusion extending from the c-ring along an axial extent of the c-ring less than the axial extent of the surface area the c-ring, for concentrating application of force radially outward by the c-ring to a smaller surface area. 
     
     
         17 . The stress relieving tool of  claim 16 , wherein the protrusion extends from the c-ring along a radial extent of the c-ring less than the radial extent of the surface area of c-ring, for concentrating application of force radially outward by the c-ring to a smaller surface area. 
     
     
         18 . The stress relieving tool of  claim 15  wherein the second tapered sleeve is anchored to the tubular to remain immobile relative to the first tapered sleeve. 
     
     
         19 . The stress relieving tool of  claim 15  further comprising a second actuator sleeve positioned on the tubular in series with the second tapered sleeve and axially opposed from the first tapered sleeve, the second actuator sleeve axially movable along the tubular and in fluid communication with the channel for advancing the second actuator sleeve along the tubular in a second direction in response to fluid pressure in the channel, the second direction axially opposed to the first direction, and wherein the second tapered sleeve is advanced in the second direction by the second actuator sleeve when the second actuator sleeve is advanced in the second direction, and the c-ring is urged radially outward when the second tapered sleeve is advanced underneath the c-ring. 
     
     
         20 . A stress relieving tool comprising:
 an elongate tubular having a channel therethrough;   a first actuator sleeve positioned on the tubular, the first actuator sleeve axially movable along the tubular and in fluid communication with the channel for advancing the first actuator sleeve along the tubular in a first direction in response to fluid pressure in the channel;   a first tapered sleeve of decreasing outer diameter in the first direction positioned on the tubular in series with the first actuator sleeve and axially movable along the tubular;   a second tapered sleeve of increasing outer diameter in the first direction positioned on the tubular in series with the first tapered sleeve;   a first stress pad positioned on the tubular between the first and second tapered sleeves; and   a second stress pad positioned on the tubular between the first and second tapered sleeves, the second stress pad radially balanced with the first stress pad;   wherein:
 the first tapered sleeve is advanced in the first direction by the first actuator sleeve when the first actuator sleeve is advanced in the first direction; and 
 the first stress pad and the second stress pad are urged radially outward from a retracted position to an actuated position when the first tapered sleeve is advanced underneath the first stress pad and the second stress pad. 
   
     
     
         21 . The stress relieving tool of  claim 20  wherein the second tapered sleeve is anchored to the tubular to remain immobile relative to the first tapered sleeve. 
     
     
         22 . The stress relieving tool of  claim 20  further comprising a second actuator sleeve positioned on the tubular in series with the second tapered sleeve and axially opposed from the first tapered sleeve, the second actuator sleeve axially movable along the tubular and in fluid communication with the channel for advancing the second actuator sleeve along the tubular in a second direction in response to fluid pressure in the channel, the second direction axially opposed to the first direction, and wherein the second tapered sleeve is advanced in the second direction by the second actuator sleeve when the second actuator sleeve is advanced in the second direction, and the first stress pad and the second stress pad are urged radially outward when the second tapered sleeve is advanced underneath the first stress pad. 
     
     
         23 . The stress relieving tool of  claim 20  further comprising:
 a first protrusion extending from the first stress pad along an axial extent of the first stress pad less than the axial extent of surface area of the first stress pad, for concentrating application of force radially outward by the first stress pad to a smaller surface area; and 
 a second protrusion extending from the second stress pad along an axial extent of the second stress pad less than the axial extent of surface area of the second stress pad, for concentrating application of force radially outward by the second stress pad to a smaller surface area. 
 
     
     
         24 . The stress relieving tool of  claim 23  wherein:
 the first protrusion extends from first stress pad along a radial extent of the first stress pad less than the radial extent of the surface area of first stress pad, for concentrating application of force radially outward by the first stress pad to a smaller surface area; and 
 the second protrusion extends from second stress pad along a radial extent of the second stress pad less than the radial extent of the surface area of second stress pad, for concentrating application of force radially outward by the second stress pad to a smaller surface area. 
 
     
     
         25 . The stress relieving tool of  claim 20  further comprising a cage positioned about the first stress pad and the second stress pad and anchored to the tubular for defining a maximum extent of actuation of the first and second stress pads. 
     
     
         26 . The stress relieving tool of  claim 20  wherein the first and second stress pads together cover at least half of the radial extent of the stress relieving tool when in the retracted position. 
     
     
         27 . The stress relieving tool of  claim 26  wherein the first and second stress pads together cover substantially the entire radial extent of the stress relieving tool when in the retracted position.