System and Method for Forming Cavities

Abstract

A technique facilitates forming cavities, e.g. perforations, into a geological formation. A jetting tool is moved downhole into a borehole, and an abrasive fluid is pumped down through the jetting tool. The abrasive fluid is discharged under pressure through a plurality of jetting nozzles to form jets of the abrasive fluid which act against a surrounding wall, e.g. a casing or other borehole wall. The jetting nozzles, and thus the jets, are oriented such that a rebound effect of the jets does not detrimentally impact the jetting tool. Consequently, the jets can be used to cut perforations through the surrounding wall and into the formation without eroding or otherwise detrimentally affecting components of the jetting tool.

What is claimed is: 
     
         1 . A system for forming perforations in a well, comprising:
 a coiled tubing; and   a jetting tool coupled to the coiled tubing by a coiled tubing connector, the jetting tool having a flow passage therein which extends along a longitudinal axis of the jetting tool to a plurality of jetting nozzles, thus forming a flow path through the flow passage and the plurality of jetting nozzles, the plurality of jetting nozzles being oriented such that a rebounded portion of fluid flowing out of the plurality of jetting nozzles and against a surrounding wall is directed to miss the jetting tool.   
     
     
         2 . The system as recited in  claim 1 , wherein each jetting nozzle of the plurality of jetting nozzles is oriented to form an acute angle with the longitudinal axis, the acute angle being between about 55 degrees and about 75 degrees. 
     
     
         3 . The system as recited in  claim 1 , wherein each jetting nozzle of the plurality of jetting nozzles is oriented to form an acute angle with the longitudinal axis, the acute angle being approximately 65 degrees. 
     
     
         4 . The system as recited in  claim 1 , wherein the jetting tool is coupled directly to the coiled tubing such that a fluid may be pumped from an interior of the coiled tubing and immediately into the flow passage of the jetting tool. 
     
     
         5 . The system as recited in  claim 1 , wherein the jetting tool further comprises a seat and a check valve received in the seat. 
     
     
         6 . The system as recited in  claim 5 , wherein the check valve comprises a ball which seals against the seat during an injection operation in which fluid flows outwardly through the plurality of jetting nozzles. 
     
     
         7 . The system as recited in  claim 5 , wherein the seat and the check valve are located along the axis of the jetting tool. 
     
     
         8 . A method, comprising:
 moving a jetting tool downhole in a wellbore drilled into a formation;   pumping an abrasive fluid down through the jetting tool and out through a plurality of jetting nozzles to form jets of the abrasive fluid which act against a surrounding wall;   orienting the jets such that a rebound effect of the jets does not detrimentally impact the jetting tool; and   using the jets to cut perforations through the surrounding wall.   
     
     
         9 . The method as recited in  claim 8 , wherein moving comprises moving the jetting tool downhole via coiled tubing. 
     
     
         10 . The method as recited in  claim 8 , wherein pumping comprises pumping the abrasive fluid down through a flow passage oriented along a longitudinal axis of the jetting tool and out through the plurality of nozzles. 
     
     
         11 . The method as recited in  claim 10 , wherein orienting the jets comprises orienting the plurality of jetting nozzles at an acute angle of between about 55 degrees and about 75 degrees with respect to the longitudinal axis. 
     
     
         12 . The method as recited in  claim 10 , wherein orienting the jets comprises orienting the plurality of jetting nozzles at an acute angle of approximately 65 degrees with respect to the longitudinal axis. 
     
     
         13 . The method as recited in  claim 9 , further comprising pulling the jetting tool uphole a predetermined distance from the perforations. 
     
     
         14 . The method as recited in  claim 13 , further comprising pumping a hydraulic fracture slurry down through an annulus between the coiled tubing and a surrounding casing and then into the perforations to fracture the formation. 
     
     
         15 . The method as recited in  claim 14 , further comprising cleaning out excess hydraulic fracture slurry by running the jetting tool back downhole while reverse circulating a clean fluid from a surface location down through the annulus, into the jetting tool through the plurality of jetting nozzles, and up through an interior of the coiled tubing. 
     
     
         16 . The method as recited in  claim 15 , wherein cleaning out further comprises returning a portion of the clean fluid through a check valve located downhole from the plurality of nozzles. 
     
     
         17 . The method as recited in  claim 15 , wherein cleaning out further comprises returning the clean fluid in its entirety through the plurality of jetting nozzles. 
     
     
         18 . A method, comprising:
 forming a jetting tool with a central axis, a flow passage extending along the central axis, and a plurality of jetting nozzles in communication with the flow passage;   orienting the plurality of nozzles at an angle with respect to the central axis; and   selecting the angle such that jets of fluid flowing outwardly through the plurality of nozzles are directed outwardly and toward a lead end of the jetting tool.   
     
     
         19 . The method as recited in  claim 18 , further comprising moving the jetting tool downhole into a wellbore lined with casing; and pumping and abrasive fluid down through the flow passage and out through the plurality of jetting nozzles to cut cavities in a surrounding wall. 
     
     
         20 . The method as recited in  claim 19 , wherein selecting comprises selecting the angle such that a rebound effect of abrasive fluid rebounding off the surrounding wall does not erode the jetting tool.