Gradually tapered coiled tubing in extended reach wellbores

Abstract

Maximum penetration of coiled tubing in extended reach horizontal wellbores is significantly increased by using a continuously tapered portion of coiled tubing. In particular, the tubing wall thickness is continuously tapered such that the well thickness gradually decreases toward the far end of the coiled tubing. The exterior dimension remains constant while the internal diameter gradually increases. The non-linear thickness profile of the tubing is optimized for extended reach in horizontal wellbores. In some cases, the thickness profile is optimized for providing a uniform axial strain on the tubing in the horizontal section of the well.

What is claimed is: 
     
         1 . A coiled tubing configured for extended reach in a horizontal portion of a well, the tubing comprising a tapered portion having a near end and a far end, and configured for deployment from a surface location into the horizontal portion of the well such that the far end is further from the surface location, the tapered portion having a tubing wall thickness that continuously and non-linearly decreases from the near end to the far end, thereby facilitating further reach into the horizontal portion of the well by the far end without buckling of the tubing when compared to non-tapered tubing, discontinuously tapered tubing and linearly tapered tubing. 
     
     
         2 . The coiled tubing according to  claim 1 , wherein the tubing wall thickness of the tapered portion decreases at an exponential rate from the near end to the far end. 
     
     
         3 . The coiled tubing according to  claim 1 , wherein the tubing wall thickness of the tapered portion has a thickness profile that is optimized for reach. 
     
     
         4 . The coiled tubing according to  claim 1  wherein the tubing wall thickness of the tapered portion has a thickness profile that is optimized for uniform axial strain along the tapered portion. 
     
     
         5 . The coiled tubing according to  claim 1 , wherein the far end of the tapered portion is fitted to a bottom hole assembly. 
     
     
         6 . The coiled tubing according to  claim 1 , further comprising a non-tapered portion joined to the near end. 
     
     
         7 . The coiled tubing according to  claim 1 , wherein the tapered portion is free of welds that join tubing having different wall thicknesses at a location of a joint. 
     
     
         8 . A method of deploying coiled tubing into a horizontal portion of a wellbore from a surface location comprising:
 lowering a tapered portion of the coiled tubing into the wellbore from the surface location, the tapered portion having near end and a far end, the far end being lowered into the wellbore first, the tapered portion having a tubing wall thickness that continuously and non-linearly decreases from the near end to the far end; and   pushing the tapered portion into the horizontal portion of the wellbore such that the far end reaches further into the horizontal portion without buckling of the tubing when compared to non-tapered tubing, discontinuously tapered tubing and linearly tapered tubing.   
     
     
         9 . The method according to  claim 8 , wherein the tubing wall thickness of the tapered portion decreases at an exponential rate from the near end to the far end. 
     
     
         10 . The method according to  claim 8 , wherein the wall thickness of the tapered portion has a thickness profile that is optimized for reach. 
     
     
         11 . The method according to  claim 8 , wherein the wall thickness of the tapered portion has a thickness profile that is optimized for uniform axial strain along the tapered portion. 
     
     
         12 . The method according to  claim 8 , wherein the wellbore includes a vertical portion above the horizontal portion, and said pushing is performed at least in part by lowering a non-tapered portion of the coiled tubing into the vertical portion, the non-tapered portion being joined to the near end of the tapered portion. 
     
     
         13 . The method according to  claim 8 , wherein the horizontal portion traverses a hydrocarbon bearing subterranean rock formation and the method further comprises performing an intervention operation on the wellbore at the location of the far end using said coiled tubing.