Method of Real Time Monitoring of Well Operations Using Self-Sensing Treatment Fluids

Abstract

Downhole conditions in a wellbore may be monitored in real time by pumping into the well a sensing treatment fluid which includes a piezoelectric or piezoresistive material and measuring changes in electrical resistivity within the wellbore. The monitoring in real time of the piezoelectric or piezoresistive material enhances the integrity of the wellbore during the setting of the treatment fluid as well as during the lifetime of the well.

What is claimed is: 
     
         1 . A method of monitoring one or more downhole conditions within a wellbore comprising pumping into the wellbore a self-sensing treatment fluid containing a piezoelectric or piezoresistive material and assessing the electrical resistivity of the self-sensing treatment fluid containing the piezoelectric or piezoresistive material within the wellbore. 
     
     
         2 . The method of  claim 1 , wherein the electrical resistivity is monitored by assessing the voltage produced by one or more thermocouples placed at pre-determined locations within the wellbore. 
     
     
         3 . The method of  claim 1 , wherein the self-sensing treatment fluid is a cementitious slurry and where the electrical resistivity is assessed during hardening of the cementitious slurry. 
     
     
         4 . The method of  claim 1 , wherein the self-sensing treatment fluid is a drilling mud and further wherein electrical resistivity is assessed in returns from the drilling mud. 
     
     
         5 . The method of  claim 1 , wherein the piezoelectric or piezoresistive material is quartz, tourmaline, ceramic, conductive fiber or a polymer. 
     
     
         6 . The method of  claim 5 , wherein the piezoelectric or piezoresistive material is:
 (a) a ceramic selected from the group consisting of zirconate titanate, barium titanate, lead niobate, and silicon carbide;   (b) polyvinylidene fluoride or an anti-static plastic; or   (c) a conductive fiber selected from the group consisting of carbon fibers and metallic fibers.   
     
     
         7 . The method of  claim 1 , wherein the downhole condition monitored is stress or strain in the wellbore. 
     
     
         8 . The method of  claim 1 , wherein the self-sensing treatment fluid is a cementitious slurry and further wherein the downhole condition monitored within the wellbore is the strengthening of the cementitious slurry. 
     
     
         9 . The method of  claim 1 , wherein the downhole condition monitored within the wellbore is the type or location of potential cross flow between zones of a subterranean formation penetrated by the wellbore. 
     
     
         10 . A method of monitoring one or more downhole conditions in a wellbore in real time, the method comprising:
 (a) pumping into the wellbore a cementitious slurry containing a piezoelectric or piezoresistive material in an amount sufficient for a monitoring device to measure the electrical resistivity of a set cement from the cementitious slurry;   (b) setting the cementitious slurry; and   (c) assessing one or more downhole conditions using a monitor receptive to the piezoelectric or piezoresistive material within the set cement.   
     
     
         11 . The method of  claim 10 , wherein the downhole condition monitored is the stability of the set cement. 
     
     
         12 . The method of  claim 10 , wherein the degree of hardness of the set cement is ascertained by comparing the real time electrical resistivity of the hardened cement at downhole conditions to resistivity values of a learning set of cements of known hardness at pressure and temperature conditions substantially similar to the downhole conditions. 
     
     
         13 . The method of  claim 12 , wherein the resistivity values of the learning set of hardened cements is determined experimentally in a cell where pressure and temperature are set to levels expected in borehole conditions. 
     
     
         14 . The method of  claim 10 , wherein the one or more downhole conditions monitored are determinative of the front of the cementitious slurry as it advances through the wellbore. 
     
     
         15 . A method of monitoring in real time one or more downhole conditions within a wellbore comprising pumping into the wellbore a cementitious slurry containing a cement mix and a piezoelectric or piezoresistive material wherein the cementitious slurry is hardened within the wellbore to form a cement sheath, the method further comprising assessing the electrical resistivity of the cement mix or the hardened cement containing the piezoelectric or piezoresistive material within the wellbore. 
     
     
         16 . The method of  claim 15 , further comprising determining the location within the wellbore of the uppermost portion of the cement sheath from the assessed electrical resistivity. 
     
     
         17 . The method of  claim 15 , further comprising determining the length of the cement sheath within the wellbore from the assessed electrical resistivity. 
     
     
         18 . The method of  claim 15 , further comprising determining the location of the cement sheath within the wellbore from the assessed electrical resistivity. 
     
     
         19 . The method of  claim 15 , wherein the location of a crack or failure within the cement sheath within the wellbore is determined from the assessed electrical resistivity. 
     
     
         20 . A method of cementing a pipe or casing in a wellbore which comprises:
 (a) introducing into the wellbore a cementitious slurry comprising a piezoelectric or piezoresistive material, wherein the piezoelectric or piezoresistive material is present in the cementitious slurry in an amount sufficient to be monitored, when the cementitious slurry has been hardened, by a monitor receptive to the piezoelectric or piezoresistive material; and   (b) allowing the slurry to harden to a solid mass.