Concentric coiled tubing annular fracturing string

Abstract

An improved concentric coiled tubing annular fracturing string is disclosed having at least two fluid flow paths. An umbilical tube located inside of a coiled tubing string may provide one of the pathways, which may be used to isolate downhole elements, such as a packer, from harmful fluids. The annulus between the umbilical tube and the outer coiled tubing may provide the second flow pathway. The umbilical tube may contain an electric line, which may provide an electrical connection to a bottom hole assembly (“BHA”). The improved system may also provide for the measurement of down hole fracturing fluid pressure or be used to deliver a cross-linking agent to a specified portion of a well. The BHA may include an emergency packer deflation device to rapidly deflate a packer in the event the packer loses its ability to anchor against the casing.

1 . A coiled tubing annular fracturing string, the string comprising: 
 a coiled tubing string;    a bottom hole assembly including an inflatable packing element, the bottom hole assembly connected to the coiled tubing string; and    an umbilical tube located within the coiled tubing string, wherein the umbilical may be used to inflate or deflate the inflatable packing element.    
   
   
       2 . The string of  claim 1  wherein the bottom hole assembly further includes an anchor.  
   
   
       3 . The string of  claim 2  wherein the umbilical tube may be used to set or release the anchor within a wellbore.  
   
   
       4 . The string of  claim 1  wherein the inflatable packing element anchors the bottom hole assembly against a casing of a wellbore when inflated.  
   
   
       5 . The string of  claim 1  further comprising an emergency deflation device in communication with the packing element, wherein the packing element is deflated if the inflated packing element is no longer anchored against the casing.  
   
   
       6 . The string of  claim 5  the emergency deflation device includes a piston rod, a piston, and a spring.  
   
   
       7 . The string of  claim 6  wherein the emergency deflation device is adapted to equalize the pressure across the inflated packing element.  
   
   
       8 . The string of  claim 1  further comprising an electric wireline located within the umbilical tube.  
   
   
       9 . The string of  claim 8  wherein the electric wireline allows communication between the surface and an element of the bottom hole assembly.  
   
   
       10 . The string of  claim 9  wherein the element is a set of perforating guns, a pressure transducer, a temperature gauge, or a casing collar locator.  
   
   
       11 . The string of  claim 1  further comprising one or more fluid ports located above the packing element.  
   
   
       12 . The string of  claim 11  wherein the coiled tubing string delivers wash fluids or circulating fluids through the one or more fluid ports to a location within the wellbore.  
   
   
       13 . The string of  claim 1  wherein the one or more fluid ports include a one way valve.  
   
   
       14 . The string of  claim 1  wherein a negative pressure is applied to the packing element through the umbilical tube to deflate the packing element.  
   
   
       15 . The string of  claim 1  further comprising a second umbilical tube located within the coiled tubing string, wherein the second umbilical provides a third fluid flow path.  
   
   
       16 . The string of  claim 15  wherein the second umbilical does not extend the entire length of the coiled tubing string.  
   
   
       17 . The string of  claim 1  wherein the umbilical tube delivers a low specific gravity fluid to the packing element.  
   
   
       18 . A coiled tubing string for use in the annular coil tubing fracturing, the coiled tubing string comprising: 
 a bottom hole assembly, the bottom hole assembly including an inflatable packing element;    a first fluid flow path, wherein the first fluid flow path may be used to deliver fluid to a desire downhole location within a wellbore; and    a second fluid flow path, wherein the second fluid flow path may deliver fluid to inflate or deflate the inflatable packing element.    
   
   
       19 . The coiled tubing string of  claim 18  further comprising an electric wireline located within the second fluid flow path.  
   
   
       20 . The coiled tubing string of  claim 18  further comprising at least one fluid port in communication with the first fluid flow path.  
   
   
       21 . The coiled tubing string of  claim 20  further comprising an one way valve preventing two way flow through the at least one fluid port.  
   
   
       22 . A coiled tubing string, the coiled tubing string comprising: 
 a first fluid flow path within the coiled tubing string;    a second fluid flow path within the coiled tubing string;    a bottom hole assembly, the bottom hole assembly including a hydraulically set anchor and an inflatable packing element;    means for requiring a first predetermined pressure within the second flow path before the anchor is set; and    means for requiring a second predetermined pressure within the second flow path before the packing element begins to inflate.    
   
   
       23 . The coiled tubing string of  claim 22  further comprising means for ensuring that the anchor is set prior to beginning to inflate the packing element and means for ensuring that the packing element deflates prior to unsetting the anchor.  
   
   
       24 . The coiled tubing string of  claim 22  further comprising means for preventing the over inflation of the packing element.  
   
   
       25 . The coiled tubing string of  claim 24  further comprising means for ensuring that the pressure within the packing element is greater than the pressure of a fracturing zone within a wellbore.  
   
   
       26 . The coiled tubing string of  claim 22  further comprising means for ensuring that the pressure within the anchor is greater than the pressure within the packing element.  
   
   
       27 . The coiled tubing string of  claim 22  wherein the second fluid flow path protects the packing element from harmful fluids present in the first fluid flow path.  
   
   
       28 . The coiled tubing string of  claim 22  wherein the second fluid flow path contains a low specific gravity fluid.  
   
   
       29 . A coiled tubing string, the coiled tubing string comprising: 
 a first fluid flow path within the coiled tubing string;    a second fluid flow path within the coiled tubing string;    a bottom hole assembly, the bottom hole assembly including an inflatable packing element;    a pressure relief valve, the pressure relief being in communication with the second fluid flow path and the packing element, wherein the pressure relief valve is biased to a closed position preventing the inflation of the packing element; and    a check valve, the check valve parallel with the pressure relief valve being in fluid communication with the second fluid flow path and the packing element.    
   
   
       30 . The coiled tubing of  claim 29  wherein the pressure relief valve requires a predetermined amount of pressure to be within the second fluid flow path before the pressure relief valve opens.  
   
   
       31 . The coiled tubing of  claim 30  wherein the second fluid flow path contains a low specific gravity fluid.  
   
   
       32 . A emergency deflation device for a coiled tubing string, the device comprising: 
 a housing connected above an inflatable packing element, the packing element being able to anchor against a casing when inflated with fluid;    a chamber within the housing, the chamber being in fluid communication with the packing element;    a piston and a piston rod positioned within the chamber;    at least one shearable element, the shearable element selectively securing the housing to the piston rod;    wherein if the packing element loses the ability to anchor against the casing the load on the packing element shears the at least one shearable element releasing the housing from the piston rod; and    wherein the housing and packing element moves away from the piston rod causing the piston to stroke within the chamber drawing the fluid out of the packing element.    
   
   
       33 . The emergency deflation device of  claim 32  further comprising a crush ring, wherein the crush ring prevents damage to the piston.  
   
   
       34 . The emergency deflation device of  claim 32  wherein the housing is adapted to equalize the pressure above and below the packing element and the piston has been stroked within the chamber.  
   
   
       35 . A method of fracturing a perforated zone of a wellbore with a coiled tubing string having at least two flow paths, the method comprising: 
 pumping a first fluid down a first flow path of a coiled tubing string to inflate a packing element to isolate a zone of a wellbore;    pumping fracturing fluid down the annulus between the coiled tubing string and the wellbore;    pumping a fluid down the second flow path of the coiled tubing string, the fluid being a wash fluid; and    circulating the wash fluid to the perforating zone through one or more fluid ports in the coiled tubing string.    
   
   
       36 . The method of  claim 35  further comprising applying a negative pressure within the first flow path of the coiled tubing string to deflate the packing element.  
   
   
       37 . The method of  claim 35  wherein the first fluid is a low specific gravity fluid.  
   
   
       38 . The method of  claim 35  further comprising communicating with a downhole element connected to the coiled tubing string to determine the temperature, pressure, or location of the fracturing zone.  
   
   
       39 . The method of  claim 38  wherein an electrical wireline located within the first flow path is used to communicate with the downhole element.  
   
   
       40 . The method of  claim 35  further comprises pumping the first fluid down the first flow path of the coiled tubing string to set an anchor.  
   
   
       41 . The method of  claim 35  wherein the inflated packing element anchors the coiled tubing string to casing of the wellbore.  
   
   
       42 . The method of  claim 35  further comprising pumping a cross-linking agent down the second flow path of the coiled tubing string.  
   
   
       43 . The method of  claim 42  further comprising circulating the cross-linking agent through the one or more fluid ports in the coiled tubing string.  
   
   
       44 . The method of  claim 35  further comprising pumping a fluid down the second flow path and circulating the fluid out of the one or more fluid ports to determine the fluid pressure of the zone of the wellbore, wherein the fluid is slowly pumped down the second flow path.  
   
   
       45 . The method  claim 35  further comprising pumping a fluid down a second flow path of the coiled tubing string, the second fluid being acid.  
   
   
       46 . The method  claim 45  further comprising circulating the acid to the perforating zone through one or more fluid ports in the coiled tubing string.  
   
   
       47 . A method of fracturing the formation of a perforated zone of a wellbore with a coiled tubing string having a first flow path and a second flow path, the method comprising: 
 pumping a first fluid down the first flow path to inflate a packing element to isolate a zone of a wellbore;    pumping fracturing fluid down the annulus between the coiled tubing string and the wellbore after the zone of the wellbore has been isolated, wherein the fracturing fluid is pumped down the annulus until the formation is fractured;    pumping a fluid down the second flow path of the coiled tubing string while the fracturing fluid is pumped down the annulus, wherein the fluid includes a cross-linking agent; and    circulating the fluid that includes the cross-linking agent to the perforating zone through one or more ports in the coiled tubing string while the fracturing fluid is pumped down the annulus.    
   
   
       48 . The method of  claim 47  further comprising pumping wash fluid down the second flow path after the fracturing fluid is no longer pumped down the annulus and circulating the wash fluid to the perforating zone through the one or more ports in the coiled tubing string.  
   
   
       49 . The method of  claim 47  further comprising pumping acid down the second flow path and circulating the acid to the perforating zone prior to pumping fracturing fluid down the annulus.  
   
   
       50 . The method of  claim 47  further comprising applying a negative pressure within the first flow path of the coiled tubing string to deflate the packing element after circulating wash fluid to the perforating zone.  
   
   
       51 . A method of fracturing a perforated zone of a wellbore with a coiled tubing string having at least two flow paths, the method comprising 
 pumping a first fluid down a first flow path to inflate a packing element to isolate a zone of a wellbore;    pumping fracturing fluid down the annulus between the coiled tubing string and the wellbore after the zone of the wellbore has been isolated, wherein the fracturing fluid is pumped down the annulus until the formation is fractured;    pumping a fluid down a second flow path of the coiled tubing string while the fracturing fluid is pumped down the annulus, wherein the fluid is a wash fluid; and    circulating the wash fluid to the perforating zone through one or more ports in the coiled tubing string while the fracturing fluid is pumped down the annulus.    
   
   
       52 . A method of fracturing a perforated zone of a wellbore with a coiled tubing string, the method comprising: 
 setting a packing element to isolate the perforated zone of the wellbore;    pumping fracturing fluid down the annulus between the coiled tubing string and the wellbore;    pumping a fluid down the coiled tubing string, the fluid being a wash fluid; and    circulating the wash fluid to the perforating zone through one or more fluid ports in the coiled tubing string.