# US 12,181,437 B2 · Systems, methods and tools for subterranean electrochemical characterization and enthalpy measurement in geothermal reservoirs > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,181,437 B2 - Document ID: US12181437B2 - Status: Granted - Kind: B2 - Application number: 17/474,560 - Filed: 2021-09-14 - Published: 2021-12-30 - Granted: 2024-12-31 - Earliest claimed: 2017-02-03 - Assignees: National Technology & Engineering Solutions of Sandia, LLC; The Board of Trustees of the Leland Stanford Junior University - Applicants: National Technology & Engineering Solutions of Sandia, LLC; The Board of Trustees of the Leland Stanford Junior University - Inventors: Grzegorz Cieslewski; Xuhua Gao; Ryan Falcone Hess; Avery T. Cashion, IV; William Corbin; Sasha Egan; Roland N. Horne - Web page: https://patentgrep.com/patent/US12181437B2 ## CPC - G01N 27/4162: {investigating the composition of gases, by the influence exerted on ionic conductivity in a liquid (conductometry in general G01N27/06; amperometric gas sensors G01N27/404)} - F24T 10/20: using underground water as working fluid; using working fluid injected directly into the ground, e.g. using injection wells and recovery wells - F24T 10/30: using underground reservoirs for accumulating working fluids or intermediate fluids - G01K 13/02: for measuring temperature of moving fluids or granular materials capable of flow - G01K 17/08: based upon measurement of temperature difference {or of a temperature} - F24T 2201/00: Prediction; Simulation - G01K 7/04: the object to be measured not forming one of the thermoelectric materials - G01K 13/026: {of moving liquids} - G01N 27/333: Ion-selective electrodes or membranes (glass electrodes G01N27/36) - Y02E 10/10: Geothermal energy - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - F24T: GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract The present disclosure is directed to systems, methods and tools that measure ionic concentrations and downhole enthalpy of a flowing geothermal fluid in real-time at high-temperature and pressure. The systems, methods and tools include measuring the concentration of selected naturally occurring ions found in the liquid phase of the geothermal fluid throughout the wellbore using novel electrochemical sensor technologies. The change in liquid-phase ion concentration will be used to calculate the proportion of liquid to steam and allow for accurate enthalpy measurements. The techniques and technologies described here can be applied to any application of electrochemical sensing in extreme environments. ## Claims ### Claim 1 An ionic strength reference electrode, comprising: a bimodal pellet comprising a first portion and a second portion; wherein the first portion comprises a plurality of composite particles comprising a graphite sphere core, a conductive coating surrounding the graphite sphere core, and an outside coating surrounding the conductive coating, and wherein the second portion comprises a salt portion; and wherein the first portion and the second portion are separate portions physically joined at an interface. ### Claim 2 (depends on 1) The ionic strength reference electrode of claim 1, further comprising: a conductor in electrical connectivity to the bimodal pellet. ### Claim 3 (depends on 1) The ionic strength reference electrode of claim 1, wherein the salt portion is a salt crystal. ### Claim 4 (depends on 3) The ionic strength reference electrode of claim 3, wherein the salt crystal is potassium chloride. ### Claim 5 (depends on 1) The ionic strength reference electrode of claim 1, wherein the salt portion is a solid pressed salt pellet. ### Claim 6 (depends on 5) The ionic strength reference electrode of claim 5, wherein the solid pressed salt pellet is formed from a chloride-containing salt powder. ### Claim 7 (depends on 1) The ionic strength reference electrode of claim 1, wherein the conductive coating is silver. ### Claim 8 (depends on 1) The ionic strength reference electrode of claim 1, wherein the outside coating is a silver-chloride layer. ### Claim 9 (depends on 1) The ionic strength reference electrode of claim 1, further comprising: a conducting element in contact with the bimodal pellet. ### Claim 10 (depends on 9) The ionic strength reference electrode of claim 9, further comprising: an inner liner contacting the conducting element. ### Claim 11 (depends on 10) The ionic strength reference electrode of claim 10, wherein the inner liner is a joining material. ### Claim 12 (depends on 11) The ionic strength reference electrode of claim 11, wherein the joining material is an epoxy. ### Claim 13 (depends on 10) The ionic strength reference electrode of claim 10, further comprising: an outer liner contacting the inner liner. ### Claim 14 (depends on 13) The ionic strength reference electrode of claim 13, wherein the outer liner is selected from the group consisting essentially of polymers, metals and ceramics. ### Claim 15 (depends on 1) The ionic strength reference electrode of claim 1, further comprising: a shell surrounding the bimodal pellet. ### Claim 16 (depends on 15) The ionic strength reference electrode of claim 15, wherein the shell is a polymer. ### Claim 17 (depends on 16) The ionic strength reference electrode of claim 16, wherein the polymer is a fluoropolymer. ### Claim 18 An ionic strength reference electrode, comprising: a bimodal pellet comprising a first portion and a second portion; wherein the first portion comprises a plurality of composite particles comprising a graphite sphere core, a conductive coating surrounding the graphite sphere core, and an outside coating surrounding the conductive coating, and wherein the second portion comprises a salt portion; and wherein the first portion and the second portion are separate portions physically joined at an interface; a conducting element in contact with the bimodal pellet; an inner liner contacting the conducting element; an outer liner contacting the inner liner; and a shell surrounding the bimodal pellet. ### Claim 19 (depends on 18) The ionic strength reference electrode of claim 18, wherein the salt portion is a solid crystal. ### Claim 20 (depends on 19) The ionic strength reference electrode of claim 19, wherein the salt crystal is potassium chloride. ### Claim 21 (depends on 18) The ionic strength reference electrode of claim 18, wherein the salt portion is a sold pressed salt pellet. ### Claim 22 (depends on 21) The ionic strength reference electrode of claim 21, wherein the solid pressed salt pellet is formed from a chloride-containing salt powder. ### Claim 23 (depends on 18) The ionic strength reference electrode of claim 18, wherein the conductive coating is silver. ### Claim 24 (depends on 18) The ionic strength reference electrode of claim 18, wherein the outside coating is a silver-chloride layer. ### Claim 25 (depends on 18) The ionic strength reference electrode of claim 18, wherein the inner liner is a joining material. ### Claim 26 (depends on 25) The ionic strength reference electrode of claim 25, wherein the joining material is an epoxy. ### Claim 27 (depends on 18) The ionic strength reference electrode of claim 18, wherein the outer liner is selected from the group consisting essentially of polymers, metals and ceramics. ### Claim 28 (depends on 18) The ionic strength reference electrode of claim 18, wherein the shell is a polymer. ### Claim 29 (depends on 28) The ionic strength reference electrode of claim 28, wherein the polymer is a fluoropolymer.