Self-powered microsensors for in-situ spatial and temporal measurements and methods of using same in hydraulic fracturing

Abstract

A delayed-activation sensor system includes at least one microsensor. The microsensor may include at least one sensor module for sensing a condition in an environment and a dissolvable coating encapsulating at least a portion of the at least one sensor module such that the dissolvable coating prevents the at least one sensor module from sensing the condition in the environment. The dissolvable coating may be dissolvable in a fluid in the environment such that the sensor module is activated after being located in the environment for a period of time. The microsensor may also include at least one energy harvester module to generate electrical power for the microsensor from the environment.

What is claimed is: 
     
         1 . A delayed-activation sensor system comprising:
 at least one microsensor comprising:
 at least one sensor module for sensing a condition in an environment; and 
 a dissolvable coating encapsulating at least a portion of the at least one sensor module such that the dissolvable coating prevents the at least one sensor module from sensing the condition in the environment, the dissolvable coating being dissolvable in a fluid in the environment such that the sensor module is activated after being located in the environment for a period of time. 
   
     
     
         2 . The delayed-activation sensor system of  claim 1 , wherein the sensor module is configured to sense a condition selected from the group consisting of temperature, pressure, pH, chemical composition, magnetic field strength, and stress. 
     
     
         3 . The delayed-activation sensor system of  claim 1 , wherein the dissolvable coating includes a coating that dissolves due to temperature, pH, and water. 
     
     
         4 . The delayed-activation sensor system of  claim 3 , wherein the dissolvable coating includes a thermal dissolvable coating, the thermal dissolvable coating being selected from a group consisting of a polyamide, polyglycolide or polyglycolic acid, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polystyrenesulfonate, quaternized amine polymers, alkoxomers, and mixtures thereof. 
     
     
         5 . The delayed-activation sensor system of  claim 3 , wherein the dissolvable coating includes a water dissolvable coating, the water dissolvable coating being selected from a group consisting of a polymer, PC polymer, cellulose, hydroxyethylcellulose, ethylcellulose, cellulose esthers, resins, and mixtures thereof. 
     
     
         6 . The delayed-activation sensor system of  claim 3 , wherein the dissolvable coating includes a pH dissolvable coating, the pH dissolvable coating being selected from a group consisting of a cationic polyacrylamide, acrylate, aminoacrylate, alkyl PEG-20, and mixtures thereof. 
     
     
         7 . The delayed-activation sensor system of  claim 1 , wherein the at least one coated microsensor has a dimension from 1 mm to 20 mm. 
     
     
         8 . The delayed-activation sensor system of  claim 1 , further comprising a support body for supporting the sensor module, and wherein the dissolvable coating encapsulates the support module. 
     
     
         9 . The delayed-activation sensor system of  claim 8 , wherein the support body has a cuboid shape, and wherein the dissolvable coating forms a spheroid shape. 
     
     
         10 . The delayed-activation sensor system of  claim 1 , wherein the microsensor is made of material that is functionally stable from a temperature of 100 C to 900 C. 
     
     
         11 . The delayed-activation sensor system of  claim 1 , wherein the microsensor further comprises at least one energy harvester module to generate electrical power for the microsensor from the environment. 
     
     
         12 . The delayed-activation sensor system of  claim 11 , wherein the energy harvester module includes an electrochemical energy harvester module including two dissimilar metals that form an electrochemical cell with a fluid in the environment. 
     
     
         13 . The delayed-activation sensor system of  claim 1 , further comprising:
 a plurality of microsensors; and   a dissolvable coating encapsulating each of the microsensors separately to form a plurality of coated microsensors.   
     
     
         14 . The delayed-activation sensor system of  claim 13 , wherein the dissolvable coating of at least one of the coated microsensors dissolves slower than the dissolvable coating of at least another of the coated microsensors such that the plurality of coated microsensors provide staggered sensor activation at different times. 
     
     
         15 . The delayed-activation sensor system of  claim 1 , further comprising at least one supersensor configured to receive sensor data from a plurality of microsensors and to retransmit the sensor data to a receiving point outside the environment. 
     
     
         16 . The delayed-activation sensor system of  claim 1 , further comprising a plurality of microsensors, wherein the dissolvable coating is configured to cause said plurality of microsensors to cluster together through electrostatic surface charge, van der Waal forces, electrostatic force, or surface polarity. 
     
     
         17 . The delayed-activation sensor system of  claim 11 , wherein the at least one energy harvester module is selected from the group consisting of a mechanical energy harvester module and a thermal energy harvester module. 
     
     
         18 . The delayed-activation sensor system of  claim 1 , further comprising wireless communication module configured to wirelessly transmit data. 
     
     
         19 . The delayed-activation sensor system of  claim 1 , further comprising at least one data storage/signal processing module configured. 
     
     
         20 . The delayed-activation sensor system of  claim 1 , further comprising processing circuitry generating location data indicative of a location of the microsensor. 
     
     
         21 . The delayed-activation sensor system of  claim 1 , further comprising a fracking mixture and a plurality of the microsensors mixed therein. 
     
     
         22 . The delayed-activation sensor system of  claim 1 , further comprising proppants and a plurality of the microsensors mixed therein. 
     
     
         23 . A self-powered microsensor for sensing a condition in an environment, the self-powered micro-sensor comprising:
 at least one energy harvester module to generate electrical power for the microsensor from the environment; and   at least one sensor module electrically coupled to the electrochemical energy harvester module.   
     
     
         24 . The self-powered microsensor of  claim 23 , wherein the at least one energy harvester module includes an electrochemical energy harvester. 
     
     
         25 . The self-powered microsensor of  claim 24 , further including a dissolvable coating covering the energy harvester module such that the dissolvable coating prevents at least one of the energy harvester module or the sensor module from being activated, the dissolvable coating being dissolvable in a fluid in the environment such that the sensor module is activated after being located in the environment for a period of time. 
     
     
         26 . A method of in-situ monitoring a hydraulic fracturing operation, the method comprising:
 injecting a plurality of dissolvable coated self-powered microsensors into a well bore;   dissolving of coating on self-powered microsensors in the well bore;   activating the self-powered microsensors; and   obtaining measurements from each of the self-powered microsensors.   
     
     
         27 . The method of  claim 26 , wherein the self-powered microsensors are injected with a fracking mixture used to perform hydraulic fracturing. 
     
     
         28 . The method of  claim 27 , wherein the measurements are obtained during the hydraulic fracturing. 
     
     
         29 . The method of  claim 28 , wherein the measurements are selected from the group consisting of temperature, pressure, location, and chemical composition. 
     
     
         30 . The method of  claim 27 , wherein the self-powered microsensors include a mechanical energy harvester module for harvesting vibration energy during the hydraulic fracturing to power the microsensors. 
     
     
         31 . The method of  claim 26 , wherein the self-powered microsensors are injected with proppants after the hydraulic fracturing. 
     
     
         32 . The method of  claim 31 , wherein the measurements are obtained from within fractures created by the hydraulic fracturing. 
     
     
         33 . The method of  claim 32 , wherein the measurements are selected from the group consisting of temperature, pressure, stresses, location, and oil presence. 
     
     
         34 . The method of  claim 26 , wherein the self-powered microsensors include a thermal energy harvester module for harvesting thermal energy to power the microsensors. 
     
     
         35 . The method of  claim 26 , wherein the self-powered microsensors include at least one electrochemical energy harvester module formed by two different metals, wherein the two different metals form an electrochemical cell with a fluid in an environment of the hydraulic fracturing. 
     
     
         36 . The method of  claim 26 , further comprising determining a location of at least some of the self-powered microsensors. 
     
     
         37 . The method of  claim 26 , further comprising creating a map during and/or after hydraulic fracturing. 
     
     
         38 . The method of  claim 26 , further comprising transmitting wireless signals between the microsensors to form a sensor network of microsensor nodes. 
     
     
         39 . The method of  claim 26 , further comprising transmitting signals from the microsensors to a collection point for telemetry. 
     
     
         40 . The method of  claim 26 , further comprising transmitting signals to and/or from the microsensors for determining locations of the microsensors using triangulation. 
     
     
         41 . The method of  claim 26 , further comprising transmitting signals to and/or from the microsensors for determining propagation paths indicative of the presence of oil.