Reverse burn power charge for a wellbore tool

Abstract

A power charge and method for actuating a wellbore tool with a power charge. The power charge may include a groove formed in the outer surface of the power charge. The power charge may include a first volume containing a first energetic material and a second volume containing a second energetic material that is a faster burning material compared to the first energetic material. The wellbore tool may include a tool body wall defining a power charge cavity. The groove formed in the outer surface of the power charge may define a gas pressure path between the tool body wall and the power charge, within the power charge cavity, when the power charge is inserted into the power charge cavity. The method may include coupling an initiator to the wellbore tool and initiating combustion of the first energetic material and the second energetic material to actuate the wellbore tool.

What is claimed is: 
     
         1 . A power charge for actuating a wellbore tool, the power charge comprising:
 a first end and a second end opposite the first end;   an outer surface extending from the first end to the second end;   a groove formed in the outer surface;   a first volume comprising a first energetic material; and   a second volume comprising a second energetic material, wherein the second energetic material is a faster burning material compared to the first energetic material.   
     
     
         2 . The power charge of  claim 1 , wherein the second volume extends from a position adjacent the first end towards the second end. 
     
     
         3 . The power charge of  claim 1 , wherein the second volume extends from a position adjacent the first end to a position adjacent the second end. 
     
     
         4 . The power charge of  claim 3 , wherein the second volume extends all the way through the power charge from the first end to the second end. 
     
     
         5 . The power charge of  claim 1 , wherein the second volume is coaxial with the first volume. 
     
     
         6 . The power charge of  claim 1 , further comprising an indentation in the power charge adjacent the first end. 
     
     
         7 . The power charge of  claim 6 , further comprising a booster positioned within the indentation. 
     
     
         8 . The power charge of  claim 6 , wherein the second volume extends from a position adjacent the indentation, in a direction away from the indentation. 
     
     
         9 . The power charge of  claim 1 , further comprising a path formed within the first energetic material for directing pressurized gas out of the power charge, wherein the second energetic material fills at least a portion of the path. 
     
     
         10 . A wellbore tool including a power charge for actuating the wellbore tool, comprising:
 a tool body wall defining a power charge cavity, wherein the power charge is positioned within the power charge cavity and the power charge includes:
 a first end and a second end opposite the first end, 
 an outer surface extending from the first end to the second end, 
 a groove formed in the outer surface, 
 a first volume comprising a first energetic material, and 
 a second volume comprising a second energetic material that is a faster burning material compared to the first energetic material. 
   
     
     
         11 . The wellbore tool of  claim 10 , further comprising an initiator holder positioned within the power charge cavity and configured for receiving and positioning an initiator adjacent to the power charge within the power charge cavity, wherein the initiator holder is configured for positioning an initiating output portion of the initiator adjacent to an ignition portion of the power charge. 
     
     
         12 . The wellbore tool of  claim 11 , wherein the ignition portion of the power charge includes the first energetic material or the second energetic material. 
     
     
         13 . The wellbore tool of  claim 12 , wherein the ignition portion of the power charge includes the second energetic material and the initiator holder is configured for positioning the initiating output portion of the initiator adjacent to the second volume. 
     
     
         14 . The wellbore tool of  claim 11 , wherein the power charge further includes an indentation in the power charge and a booster positioned within the indentation, wherein the initiator holder is configured for positioning the initiating output portion of the initiator adjacent to the booster. 
     
     
         15 . The wellbore tool of  claim 10 , further comprising a channel open to and extending, through the tool body wall, from the power charge cavity to an outside of the tool body wall. 
     
     
         16 . The wellbore tool of  claim 15 , wherein the groove defines a gas pressure path between the tool body wall and the power charge, within the power charge cavity, and the gas pressure path is open to the channel. 
     
     
         17 . The wellbore tool of  claim 10 , further comprising a path formed within the first energetic material for directing pressurized gas out of the power charge, wherein the second energetic material fills at least a portion of the path. 
     
     
         18 . A method for actuating a wellbore tool with a power charge, comprising:
 providing the wellbore tool including a power charge cavity defined by a tool body wall of the wellbore tool;   inserting the power charge into the power charge cavity, wherein the power charge includes
 a first end and a second end opposite the first end, 
 an outer surface extending from the first end to the second end, 
 a groove formed in the outer surface, wherein the groove is configured for defining a gas pressure path between the tool body wall and the power charge, within the power charge cavity, when the power charge is inserted into the power charge cavity, 
 a first volume comprising a first energetic material, and 
 a second volume comprising a second energetic material that is a faster burning material compared to the first energetic material; and 
   coupling an initiator to the wellbore tool, wherein the initiator is configured for initiating an ignition portion of the power charge and thereby causing combustion of the first energetic material and the second energetic material and generation of gas pressure from combustion of the first energetic material and the second energetic material, wherein the gas pressure travels along the gas pressure path and actuates the wellbore tool.   
     
     
         19 . The method of  claim 18 , wherein the tool body wall includes a channel open to and extending through the tool body wall, from the power charge cavity to an actuation chamber of the wellbore tool, and the gas pressure builds up in the actuation chamber to actuate the wellbore tool. 
     
     
         20 . The method of  claim 19 , wherein the gas pressure path is open to the channel.