Hydraulic fracture geometry monitoring with downhole distributed strain measurements

Abstract

A system for use with a subterranean well can include a distributed strain sensor that senses strain along a casing which lines a treatment wellbore. The distributed strain sensor can extend across at least one fracture that intersects the wellbore. A method of monitoring at least one fracture in a subterranean well can include sensing strain in a portion of a casing where the fracture intersects the casing, the sensing being performed with a distributed strain sensor, and determining a geometry of the fracture, based on the sensing. The geometry can include a width of the fracture, a height of the fracture and an orientation of the fracture relative to a wellbore. The distributed strain sensor can include an optical waveguide.

What is claimed is: 
     
         1 . A system for use with a subterranean well, the system comprising:
 a distributed strain sensor that senses strain along a casing which lines a treatment wellbore,   wherein the distributed strain sensor extends across at least one fracture that intersects the wellbore.   
     
     
         2 . The system of  claim 1 , wherein the distributed strain sensor comprises an optical waveguide. 
     
     
         3 . The system of  claim 2 , further comprising an optical interrogator that detects optical scatter in the optical waveguide. 
     
     
         4 . The system of  claim 1 , wherein the distributed strain sensor is positioned external to the casing. 
     
     
         5 . The system of  claim 1 , wherein the fracture extends outwardly from the casing into an earth formation penetrated by the wellbore. 
     
     
         6 . The system of  claim 1 , wherein the distributed strain sensor extends across multiple perforated sections of the casing, and wherein fracture initiation at each of the perforated sections is indicated respectively by the strain in the casing sensed by the distributed strain sensor at each of the perforated sections. 
     
     
         7 . The system of  claim 1 , wherein closure of the fracture is indicated by a reduction of the strain in the casing sensed by the distributed strain sensor. 
     
     
         8 . The system of  claim 1 , wherein a change in a geometry of the fracture is correlated to a change in fluid flow between the wellbore and an earth formation penetrated by the wellbore. 
     
     
         9 . A method of monitoring at least one fracture in a subterranean well, the method comprising:
 sensing strain in a portion of a casing where the fracture intersects the casing, the sensing being performed with a distributed strain sensor; and   determining a geometry of the fracture, based on the sensing.   
     
     
         10 . The method of  claim 9 , wherein the geometry comprises a selected one or more of the group consisting of a width of the fracture, a height of the fracture and an orientation of the fracture relative to a wellbore. 
     
     
         11 . The method of  claim 9 , further comprising performing the strain sensing and geometry determining over time, thereby detecting changes in the geometry of the fracture over time. 
     
     
         12 . The method of  claim 9 , wherein the distributed strain sensor is positioned external to the casing. 
     
     
         13 . The method of  claim 9 , wherein the distributed strain sensor extends across the fracture. 
     
     
         14 . The method of  claim 9 , wherein the distributed strain sensor comprises an optical waveguide. 
     
     
         15 . The method of  claim 9 , wherein an optical interrogator detects optical scatter in the optical waveguide. 
     
     
         16 . The method of  claim 9 , further comprising correlating a change in the geometry of the fracture to a change in fluid flow between a wellbore and an earth formation penetrated by the wellbore. 
     
     
         17 . A system for use with a subterranean well, the system comprising:
 a distributed strain sensor that senses strain along a casing which lines a wellbore, the distributed strain sensor comprising an optical waveguide,   wherein the distributed strain sensor extends across at least one fracture that intersects the wellbore.   
     
     
         18 . The system of  claim 17 , further comprising an optical interrogator that detects optical scatter in the optical waveguide. 
     
     
         19 . The system of  claim 17 , wherein the fracture extends outwardly from the casing into an earth formation penetrated by the wellbore. 
     
     
         20 . The system of  claim 17 , wherein closure of the fracture is indicated by a reduction of the strain in the casing sensed by the distributed strain sensor.