# US 11,078,577 B2 · Fiber optics to monitor pipeline cathodic protection systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,078,577 B2 - Document ID: US11078577B2 - Status: Granted - Kind: B2 - Application number: 14/989,582 - Filed: 2016-01-06 - Published: 2017-07-06 - Granted: 2021-08-03 - Earliest claimed: 2016-01-06 - Assignees: Saudi Arabian Oil Company - Applicants: Saudi Arabian Oil Company - Inventors: Saeed Omar Aljabri - Web page: https://patentgrep.com/patent/US11078577B2 ## CPC - C23F 13/22: Monitoring arrangements therefor - C23F 13/04: Controlling or regulating desired parameters - F16L 58/00: Protection of pipes or pipe fittings against corrosion or incrustation (compound tubes F16L9/14) - F17D 5/00: Protection or supervision of installations (arrangements for protecting foundations E02D31/00; protecting pipes from damage or internal or external wear F16L57/00, against corrosion and scale F16L58/00; investigation of the fluid-tightness of structures G01M3/00) - G01R 15/246: {based on the Faraday, i.e. linear magneto-optic, effect} - G01R 33/032: using magneto-optic devices, e.g. Faraday {or Cotton-Mouton effect} - C23F 2213/32: Pipes - C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25 - F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL - F17D: PIPE-LINE SYSTEMS; PIPE-LINES (pumps or compressors F04; fluid dynamics F15D; valves or the like F16K; pipes, laying pipes, supports, joints, branches, repairing, work on the entire line, accessories F16L; steam traps or the like F16T; fluid-pressure electric cables H01B9/06) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A system implementing fiber optics to monitor pipeline cathodic protection systems includes a cathodic protection system coupled to a hydrocarbon pipeline and a fiber optic system connected to the cathodic protection system. The cathodic protection system passes a current through the hydrocarbon pipeline to control corrosion of the hydrocarbon pipeline. The fiber optic system measures the current flowing through the hydrocarbon pipeline over time and provides the measured current. ## Claims ### Claim 1 A system comprising: a cathodic protection system coupled to an underground hydrocarbon pipeline, the underground hydrocarbon pipeline comprises a first portion and a second portion buried in aerated soil, and a third portion positioned between the first portion and the second portion, the third portion buried in non-aerated soil, the cathodic protection system configured to pass a current through the hydrocarbon pipeline to control corrosion of the hydrocarbon pipeline; a fiber optic system connected to the cathodic protection system, the fiber optic system comprising a fiber optic cable coiled around the underground hydrocarbon pipeline, wherein a first number of coils of the fiber optic cable around the first portion and the second portion is different from a second number of coils of the fiber optic cable around the third portion, wherein the first number of coils is based on a resistivity of soil in which the first portion and the second portion are buried, and the second number of coils is based on a resistivity of soil in which the third portion is buried, the fiber optic system configured to measure in real time the current flowing through the hydrocarbon pipeline over time and provide the measured current, and wherein the fiber optic system comprises a signal processor to determine a current density of the current and compare the current density to a current density threshold. ### Claim 2 (depends on 1) The system of claim 1, wherein the fiber optic system comprises: a light generator connected to the fiber optic cable, the light generator configured to generate light to pass through the fiber optic cable; a polarimeter connected to the fiber optic cable, the polarimeter configured to detect reflected light that passes through the fiber optic cable, the reflected light generated in response to a reflection of the generated light; and the signal processor connected to the fiber optic cable, the light generator and the polarimeter, the signal processor configured to determine a quantity of current flowing through the hydrocarbon pipeline at a time instant based at least on a magnetic field generated by the current flowing through the hydrocarbon pipeline and the reflection of the light passing through the fiber optic cable, wherein the fiber optic system is configured to provide the measured current to a test station in real time. ### Claim 3 (depends on 2) The system of claim 2, wherein the polarimeter is configured to detect properties of the reflected light comprising a reflection angle and a quantity of the reflected light, and wherein the signal processor is configured to detect a plurality of quantities of current at a corresponding plurality of time instants. ### Claim 4 (depends on 3) The system of claim 3, wherein the signal processor is configured to determine the current density based on the plurality of quantities of the current flowed through the hydrocarbon pipeline by the cathodic protection system, wherein the first number of coils is correlative with the current density on the first portion and second portion, and wherein the second number of coils is correlative with the current density on the third portion. ### Claim 5 (depends on 4) The system of claim 4, wherein the current density and the threshold current density comprise units of current per area, wherein the hydrocarbon pipeline comprises wellbore tubing, and wherein the signal processor is configured to determine the quantity of current based on the reflection angle and the quantity of the reflected light. ### Claim 6 (depends on 4) The system of claim 4, wherein, based on a result of the comparing, the signal processor is configured to: determine that the current density does not satisfy the threshold current density; and cause the cathodic protection system to modify a specified current passed to the hydrocarbon pipeline to modify the current density to satisfy the threshold current density, wherein the threshold current density is correlative with soil resistivity. ### Claim 7 (depends on 2) The system of claim 2, wherein the fiber optic cable is coiled around a length of the hydrocarbon pipeline, wherein the first number of coils per unit length of the first portion and the second portion is different from the second number of coils of the fiber optic cable per unit length of the third portion, wherein the threshold current density is correlative with a surface area of the hydrocarbon pipeline to be protected. ### Claim 8 (depends on 1) The system of claim 1, wherein the threshold current density is correlative with a coating on the hydrocarbon pipeline wherein the fiber optic cable is coiled around each of the first portion, the second portion and the third portion. ### Claim 9 (depends on 7) The system of claim 7, wherein the hydrocarbon pipeline is a horizontal drill string in a horizontal wellbore drilling system, and wherein the threshold current density is in a range of 0.1 milliamps per square meter (mA/m2) to 1.25 mA/m2. ### Claim 10 (depends on 2) The system of claim 2, wherein the cathodic protection system is configured to pass a specified current to the hydrocarbon pipeline and the fiber optic system is configured to detect the current flowing through the hydrocarbon pipeline over time while hydrocarbons are flowing through the hydrocarbon pipeline, wherein the light generator, the polarimeter, and the signal processor are housed together in a single housing, wherein a time interval between a determination of a quantity of the current and output of the quantity value by the signal processor to a test station is less than 1 microsecond, and wherein the resistivity of soil in which the third portion is buried is different than the resistivity of soil in which the first portion and second portion are buried. ### Claim 11 A method comprising: passing a specified quantity of current to an underground hydrocarbon pipeline to control external corrosion of the underground hydrocarbon pipeline, wherein a quantity of current flowing through the underground hydrocarbon pipeline is affected by the external corrosion of the underground hydrocarbon pipeline, wherein the underground hydrocarbon pipeline comprises a first portion, a second portion and a third portion positioned between the first portion and the second portion; monitoring reflected light passing through a fiber optic cable coiled around the underground hydrocarbon pipeline, wherein the reflected light is modulated by a magnetic field produced by the quantity of current flowing through the underground hydrocarbon pipeline, wherein the fiber optic cable is coiled around the underground hydrocarbon pipeline, wherein a first number of coils of the fiber optic cable around the first portion and the second portion is based on a resistivity of soil in which the first portion and the second portion are buried, and a second number of coils of the fiber optic cable around the third portion is based on a resistivity of soil in which the third portion is buried; determining, based on the monitored reflected light, the quantity of current flowing through the underground hydrocarbon pipeline; determining a current density of the current flowed through the underground hydrocarbon pipeline by the cathodic protection system; and comparing the determined current density with a threshold current density. ### Claim 12 (depends on 11) The method of claim 11, wherein monitoring the reflected light passing through the fiber optic cable coiled around the underground hydrocarbon pipeline comprises: passing light generated by a light generator through the fiber optic cable; detecting the reflected light that passes through the fiber optic cable, the reflected light generated in response to a reflection of the generated light; and determining in real time the quantity of the current flowing through the underground hydrocarbon pipeline based at least on a magnetic field generated by the current flowing through the underground hydrocarbon pipeline and the reflection of the light passing through the fiber optic cable. ### Claim 13 (depends on 12) The method of claim 12, wherein determining the quantity of the current flowing through the underground hydrocarbon pipeline comprises determining a plurality of quantities of current flowing through the underground hydrocarbon pipeline at a corresponding plurality of time instants. ### Claim 14 (depends on 13) The method of claim 13, determining the threshold current density, wherein the current density comprises units of current per area, wherein the hydrocarbon pipeline comprises wellbore tubing, and wherein the threshold current density is correlative with a coating on. ### Claim 15 (depends on 14) The method of claim 14, comprising varying the first number of coils for the current density on the first portion and the second portion, and varying the second number of coils for the current density on the third portion, wherein the threshold current density is in a range of 0.1 milliamps per square meter (mA/m2) to 1.25 mA/m2. ### Claim 16 (depends on 14) The method of claim 14, wherein, based on a result of the comparing: determining that the current density does not satisfy the threshold current density; and modifying the specified current passed to the underground hydrocarbon pipeline to satisfy the threshold current density, wherein the first number of coils along a unit length of the first portion and the second portion is different than the second number of coils along the unit length of the third portion, and wherein the light generator, the polarimeter, and the signal processor are housed together in a single housing. ### Claim 17 (depends on 11) The method of claim 11, wherein the underground hydrocarbon pipeline is a horizontal drill string in a horizontal wellbore drilling system, and wherein determining the quantity of current comprises determining the quantity of current and providing the determined quantity value to a test station in real time. ### Claim 18 A method comprising: coiling a fiber optic cable around an underground hydrocarbon pipeline connected to a cathodic protection system configured to pass a specified quantity of current to the underground hydrocarbon pipeline to control external corrosion of the underground hydrocarbon pipeline, wherein a quantity of current flowing through the underground hydrocarbon pipeline is affected by the external corrosion of the underground hydrocarbon pipeline, wherein the underground hydrocarbon pipeline comprises a first portion and a second portion positioned in aerated soil, and a third portion positioned in non-aerated soil and between the first portion and the second portion, wherein a first number of coils of the fiber optic cable around the first portion and the second portion is different from a second number of coils of the fiber optic cable around the third portion, wherein the first number of coils is based on a resistivity of soil in which the first portion and the second portion are buried, and the second number of coils is based on a resistivity of soil in which the third portion is buried; passing light through the fiber optic cable; monitoring reflected light passing through a fiber optic cable in response to the light, wherein the reflected light is modulated by the quantity of current flowing through the underground hydrocarbon pipeline; determining in real time, based on the monitored reflected light, the quantity of current flowing through the underground hydrocarbon pipeline; determining a current density of the current; and comparing the current density with a threshold current density. ### Claim 19 (depends on 18) The method of claim 18, comprising determining the threshold current density correlative with a coating on the underground hydrocarbon pipeline. ### Claim 20 (depends on 19) The method of claim 19, wherein the threshold current density is in a range of 0.1 milliamps per square meter (mA/m2) to 1.25 mA/m2.