Downhole strain sensing cables

Abstract

A downhole strain sensing cable includes a core optical unit which includes a plurality of optical fibers. A fiber-reinforced polymer matrix layer surrounds and contacts the core optical unit. An extrusion layer surrounds and contacts the fiber-reinforced polymer matrix layer. An outer metal tube surrounds and contacts the extrusion layer.

1 - 21 . (canceled) 
     
     
         21 . A downhole strain sensing cable comprising:
 a core optical unit comprising at least one optical fiber;   a reinforced polymer matrix layer surrounding and contacting the core optical unit;   an extrusion layer surrounding the reinforced polymer matrix; and   an outer tube surrounding the extrusion layer,   wherein the cable is rated to 150 degrees Celsius.   
     
     
         22 . The downhole strain sensing cable of  claim 21 , wherein less than or equal to four optical fibers are included in the core optical unit. 
     
     
         23 . The downhole strain sensing cable of  claim 21 , wherein the at least one optical fiber comprises at least one single mode optical fiber and at least one multi-mode optical fiber. 
     
     
         24 . The downhole strain sensing cable of  claim 21 , wherein the at least one optical fiber is stranded along a length of the cable with a lay length of between 90 millimeters and 350 millimeters. 
     
     
         25 . The downhole strain sensing cable of  claim 21 , wherein the core optical unit further comprises a cladding and a jacket, the cladding encasing the at least one optical fiber, the jacket surrounding the cladding. 
     
     
         26 . The downhole strain sensing cable of  claim 25 , wherein the cladding is formed from silicone and the jacket is formed from a fluoropolymer. 
     
     
         27 . The downhole strain sensing cable of  claim 21 , wherein the reinforced polymer matrix comprises a fiber reinforced polymer matrix. 
     
     
         28 . The downhole strain sensing cable of  claim 27 , wherein the polymer matrix of the fiber reinforced polymer matrix layer comprises one of a polyester resin, an acrylic-based resin, a terephthalic resin, or a vinyl ester resin. 
     
     
         29 . The downhole strain sensing cable of  claim 21 , wherein the extrusion layer comprises a foamed polymer extrusion. 
     
     
         30 . The downhole strain sensing cable of  claim 21 , wherein the extrusion layer is free from reinforcing fibers. 
     
     
         31 . The downhole strain sensing cable of  claim 21 , wherein the outer tube comprises metal. 
     
     
         32 . The downhole strain sensing cable of  claim 31 , wherein the metal comprises a steel. 
     
     
         33 . The downhole strain sensing cable of  claim 21 , wherein a maximum outer diameter of the outer tube is less than 0.3 inches. 
     
     
         34 . A downhole strain sensing cable comprising:
 a core optical unit comprising at least one optical fiber;   a reinforced polymer matrix layer surrounding and contacting the core optical unit; and   an outer tube surrounding the reinforced polymer matrix layer,   wherein the cable has a yield strength of at least 2200 lbf at no greater than 0.48% strain as measured after ageing at 150 degrees Celsius for 30 days.   
     
     
         35 . The downhole strain sensing cable of  claim 34 , wherein the cable further comprises an extrusion layer disposed between the reinforced polymer matrix layer and the outer tube. 
     
     
         36 . The downhole strain sensing cable of  claim 35 , wherein the cable is configured to bend such that the core optical unit, reinforced polymer matrix layer, the extrusion layer, and the outer tube move as a single unit when strain-inducing events are encountered. 
     
     
         37 . The downhole strain sensing cable of  claim 34 , wherein the outer tube comprises metal. 
     
     
         38 . The downhole strain sensing cable of  claim 34 , wherein the polymer matrix of the reinforced polymer matrix layer comprises one of a polyester resin, an acrylic-based resin, a terephthalic resin, or a vinyl ester resin. 
     
     
         39 . The downhole strain sensing cable of  claim 34 , wherein a maximum outer diameter of the outer tube is less than 0.3 inches. 
     
     
         40 . A downhole strain sensing cable comprising:
 a core optical unit comprising at least one optical fiber;   a reinforced polymer matrix layer surrounding and contacting the core optical unit; and   an extrusion layer surrounding the reinforced polymer matrix,   wherein the cable has a yield strength of at least 2200 lbf at no greater than 0.48% strain as measured after ageing at 150 degrees Celsius for 30 days.