Patent EA-003172-B1 (EA)
Title: Downhole well corrosion monitoring apparatus and method
Inventor: JOHNSON BARRY V
IPC: E21B47/00
Filed: 1999-07-14
Abstract: 1. A downhole corrosion monitoring apparatus for determining the condition of a section of a well tubing string or a well casing string the apparatus comprising: (a) a plurality of piezoelectric transducers arranged in a fixed array, spaced longitudinally and axially from each other and affixed about the circumference of the sections of tubing or casing string to be monitored; (b) a microprocessor electrically connected to the transducers for activating the transducers and for receiving and transmitting signals produced by the transducers; (c) an electrical power source and conducting means extending from the power source to the microprocessor, (d) control and instrumentation means for activating the microprocessor and for receiving, recording and processing the data output signals of the microprocessor, and (e) display means in association with the control and instrumentation means for displaying data relating to corrosion rate and location of defects is the section of the tubing, or casing string. 2.The apparatus of claim 1 where the piezoelectric transducer comprises a material selected from the group consisting of quartz ceramics, polymers and hybrids formed from quartz ceramics and polymers. 3. The apparatus of claim 1 or 2 where a plurality of sections of a tubing string or casing string or both. are monitored for rate of corrosion. 4. The apparatus of any of claims 1 to 3 where the fixed array of transducers comprises at least three longitudinally spaced transducers. 5. The apparatus of any of claims 1 to 3 where the fixed array of transducers comprises a plurality of longitudinally spaced transducers extending 360 degree around the circumference of the tubing or casing string. 8. The apparatus of any of claims 1 to 7 in which the transducers are attached to a section of the tubing or the casing string that is intermediate joist connectors. 9. The apparatus of any of claims 1 to 7 is which the transducers are attached to a joint connector, which joint connector, is fabricated from a material that is the same as or similar to the material of the associated tubing or casing string. 10. The apparatus of claim 7 in which the joint connector is provided with a groove extending around its circumference, and the transducers are attached to the bottom of the groove. 11. The apparatus of any of claims 1 to 10 which further comprises at least one reference block that is isolated from the source of corrosion and a pluality of transducers affixed to the reference block. 12. The apparatus of claim 11 in which the reference block is made of a material that is same or similar to the material of the associated casing or tubing. 13. The apparatus of claim 11 or 12 in which the reference block has sections of differing thickness and at least two transducers are affixed to each such section. 14. The apparatus of any of claims 1 to 13 in which the transducers (26,62) are surrounded by a protective cover. 15. The apparatus of claim 14, in which the protective cover is fabricated from a material that is the same as or similar to the material of the section of the tubing or casing string to which it is attached. 16. The apparatus of claim 14 or 13 in which a fixed array of transducers is attached to the interior surface of the protective covers. 17. The apparatus of any of claims 14 to 16 which the microprocessor attached to the transducer array is enclosed by tike protective cover. 18. The apparatus of any of claim 1 to 17 which the microprocessor is located proximate the transducers to which it is connected. 19. The apparatus of any of claims 1 to 18 in which the fixed array of transducers is attached to a short section of tubing pipe or casing pipe for assembly into a string. 20. The apparatus of any of claims 1 to 19 where the electrical power source is selected from the group consisting of batteries, a DC power supply main, and, thermoelectric generators. 21. The apparatus of any of claims 1 to 20 where the power source is located at the surface proximate the tubing or casing section to be monitored. 22. A method for the downhole corrosion monitoring of at least one section of a well tubing string or casing string, said method comprising the steps of: (a) attaching a plurality of piezoelectric transduceral in a longitudinally and radially-spaced first fixed array on the surface of at least one section of one tubing string or casing string or both; (b) electrically connecting a programmed microprocessor to the first fixed array of transducers (26) and to a source of electrical power; (c) providing control, data receiving, processing, display and storage means for transmitting electrical signals to and receiving signals from the microprocessor; (d) transmitting signals to the microprocessor to activate the transducers; (e) receiving signals from the transducers and transmitting the signals via the microprocessor to the data receiving and processing means; (f) processing the data relating to the presence of corrosion and defects in the section of the string being monitored and displaying the processed data on the display means. 23. The method of claim 22 in which the signals to the microprocessor are transmitted intermittently. 24. The method of claim 22 or 23 comprising the further steps of: providing a reference block fabricated from a material that is the same as or similar to the material of the string being monitored; affixing the reference block proximate the first fixed array of transducers in isolated relation to the string; obtaining data on the condition of the reference block from transducers and microprocessors associated with the block; and comparing the data relating to the condition of the reference block to the data relating to the section of the string being monitored. 25. The method of any of claims 22 to 24 in which a plurality of transducer arrays and electrically connected microprocessors are attached to a plurality of spaced apart sections of the tubing or casing strings or both the tubing and casing strings. 26. The method of any of claims 22 to 25 which comprises the further steps of: providing a protective cover fabricated from a material that is the same as or similar to the material of the section of the string being monitored; installing the cover to enclose the fixed array of transducers on the exterior surface of the section; attaching a plurality of transducers and an associated microprocessor to the interior of the protective cover to form a second fixed array; and obtaining data from the first and second fixed arrays, to thereby determine the comparative internal and external condition of the surfaces of the section being monitored with respect to the reference block. 27. The method of any of claims 22 to 26 where the at least one section of well tubing or casing string is in a producing oil well.