Downhole fluid-pressure safety bypass method

Abstract

A method of downhole fluid-pressure safety bypass for coiled-tubing operations, which diverts excessively pressurized drilling fluid directly into the annulus, protecting the fluid motor and similar downhole equipment from damage or reduced function, while allowing greater fluid pressures to be used up-hole for purposes such as increasing the flushing of cuttings up the annulus.

I claim: 
     
         1 . A downhole fluid-pressure safety bypass method for coiled-tubing operations having an annulus and having an up-hole and downhole orientation, on a workstring having a central axial conduit for drilling fluid of a standard cross-sectional area, and a desired maximum pressure of drilling fluid in the downhole side of the workstring, the downhole fluid-pressure safety bypass comprising:
 (i) providing a downhole fluid-pressure safety bypass apparatus comprising:
 (a) an intake tube section adapted to mount at an up-hole end to a coiled-tubing workstring, having at an up-hole end extending to the middle portion of said intake tube section a central axial conduit for drilling fluid of a first cross-sectional area smaller than standard, and having an enlargement of cross-sectional area at a downhole end, defining a shoulder; 
 (b) an outflow tube section adapted to mount at an up-hole end to the downhole end of said intake tube section, and mount at a downhole end to the downhole continuation of the coiled-tubing workstring, having a central axial conduit for drilling fluid of size close to the first cross-sectional area of said intake tube section, and having an enlargement of cross-sectional area at a downhole end; 
 (c) at least one fluid bypass port adapted to allow passage of drilling fluid from the middle portion of the central axial conduit of said intake tube section to the annulus; 
 (d) a calibrated coiled spring adapted to fit into the enlarged-cross-sectional area of said intake tube section such that said calibrated coiled spring does not bind and does not block the flow of drilling fluid; and 
 (e) a flow-through sliding inner tube having an external size matching the first cross-sectional area of said intake tube section at an up-hole end, and having an increased external size larger than the first cross-sectional area of said intake tube section, defining a shoulder, at a downhole end, and having a central axial conduit for drilling fluid, adapted to slide inside said intake tube section and to block said fluid bypass ports when at an up-hole position and to not block said fluid bypass ports when at a downhole position; 
   (ii) using said downhole fluid-pressure safety bypass apparatus where, in use, at fluid pressures up to the desired maximum, said flow-through sliding inner tube is pressed by said calibrated coiled spring into an up-hole position such that the shoulder of said flow-through sliding inner tube is stopped by contact with the shoulder of said intake tube section and said flow-through sliding inner tube blocks said fluid bypass ports, and all of the fluid flows through said flow-through sliding inner tube into said outflow tube section and into the downhole continuation of the coiled-tubing workstring;   and where, in use, at fluid pressures above the desired maximum, said flow-through sliding inner tube is pressed to overcome said calibrated coiled spring and to slide into a downhole position such that said flow-through sliding inner tube does not block said fluid bypass ports, and a portion of the fluid flows through said fluid bypass ports into the annulus; and   (iii) preventing excessively pressurized drilling fluid from flowing into the downhole continuation of the coiled-tubing workstring by diverting a portion of drilling fluid through said fluid bypass ports directly into the annulus, thereby increasing flow up the annulus.   
     
     
         2 . The downhole fluid-pressure safety bypass method of  claim 1 , where said downhole fluid-pressure safety bypass apparatus further comprises being made of steel. 
     
     
         3 . The downhole fluid-pressure safety bypass method of  claim 1 , where said intake tube section, said outflow tube section, and said flow-through sliding inner tube further have the form of round tubes. 
     
     
         4 . The downhole fluid-pressure safety bypass method of  claim 1 , where said intake tube section and said outflow tube section have a largest external-surface diameter of between 2 and 2.5 inches, inclusive. 
     
     
         5 . The downhole fluid-pressure safety bypass method of  claim 1 , where said flow-through sliding inner tube further comprises having a central axial conduit with a tapered decreasing cross-sectional area. 
     
     
         6 . The downhole fluid-pressure safety bypass method of  claim 1 , where said downhole fluid-pressure safety bypass apparatus further comprises more than one said fluid bypass port. 
     
     
         7 . The downhole fluid-pressure safety bypass method of  claim 1 , where said downhole fluid-pressure safety bypass apparatus further comprises more than two said fluid bypass ports. 
     
     
         8 . The downhole fluid-pressure safety bypass method of  claim 1 , where said downhole fluid-pressure safety bypass apparatus further comprises more than one said fluid bypass ports distributed radially about said intake tube section. 
     
     
         9 . The downhole fluid-pressure safety bypass method of  claim 1 , where said downhole fluid-pressure safety bypass apparatus further comprises more than one said fluid bypass ports distributed equidistantly about said intake tube section.