Nuclear magnetism logging tool using high-temperature superconducting squid detectors
Patent 4987368 Issued on January 22, 1991. Estimated Expiration Date: 
August 31, 2009. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 31, 2009. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3462674 Zeugmatography process Oil well logging tools measuring paramagnetic logging effect for use in open boreholes and cased well bores Inspection apparatus based on nuclear magnetic resonance Patent #: 4777443 InventorAssigneeApplicationNo. 403042 filed on 08/31/1989US Classes:324/303Using well logging deviceExaminersPrimary: Tokar, MichaelAssistant: Arana, Louis Foreign Patent References
International ClassG01V 003/00AbstractA logging device is disclosed for measuring the nuclear magnetism response of earth formations. The device employs a detector that is capable of detecting sinusoidal and slowly varying changes in magnetic field caused by precession of mobile nuclei about the earth's magnetic field. Such a detector may be one or more laser-pumped helium magnetometers, or one or more high-temperature Superconducting Quantum Interference Devices (SQUID). The invention uses a micro-miniature Joule-Thomson refrigerator to maintain the high-temperature SQUIDs below their superconducting transition point. The SQUIDs are flux coupled in an axial gradiometer configuration to reduce motion-induced magnetic noise.Other References
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