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Title: Use of earth field spin echo NMR to search for liquid minerals

Abstract

An instrument for measuring the spatial, qualitative and quantitative parameters of an underground nuclear magnetic resonance (NMR) active liquid mineral deposit, including oil and water. A phased array of excitation and receiver antennas on the surface and/or in a borehole excites the NMR active nuclei in the deposit, and using known techniques from magnetic resonance imaging (MRI), the spatial and quantitative distribution of the deposit can be measured. A surface array may utilize, for example, four large (50-500 diameter) diameter wire loops laid on the ground surface, and a weak (1.5-2.5 kHz) alternating current (AC) field applied, matching the NMR frequency of hydrogen in the rather flat and uniform earth magnetic field. For a short duration (a few seconds) an additional gradient field can be generated, superimposed to the earth field, by applying direct current (DC) to the grid (wire loops), enhancing the position sensitivity of the spin-echo and also suppressing large surface water signals by shifting them to a different frequency. The surface coil excitation can be combined with downhole receivers, which are much more radio-quiet compared to surface receivers, and this combination also enhances the position resolution of the MRI significantly. A downhole receiver module, for example, maymore » have a 5.5 inch diameter and fit in a standard six inch borehole having a one-quarter inch thick stainless steel casing. The receiver module may include more than one receiver units for improved penetration and better position resolution.« less

Inventors:
 [1]
  1. (Livermore, CA)
Issue Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
OSTI Identifier:
873510
Patent Number(s):
6177794
Assignee:
Regents of University of California (Oakland, CA) LLNL
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
earth; field; spin; echo; nmr; liquid; minerals; instrument; measuring; spatial; qualitative; quantitative; parameters; underground; nuclear; magnetic; resonance; active; mineral; deposit; including; oil; water; phased; array; excitation; receiver; antennas; surface; borehole; excites; nuclei; techniques; imaging; mri; distribution; measured; utilize; example; 50-500; diameter; wire; loops; laid; ground; weak; 5-2; khz; alternating; current; applied; matching; frequency; hydrogen; flat; uniform; duration; additional; gradient; generated; superimposed; applying; direct; dc; grid; enhancing; position; sensitivity; spin-echo; suppressing; signals; shifting; coil; combined; downhole; receivers; radio-quiet; compared; combination; enhances; resolution; significantly; module; inch; fit; standard; six; one-quarter; thick; stainless; steel; casing; units; improved; penetration; resonance imaging; inch thick; wire loop; magnetic resonance; direct current; magnetic field; stainless steel; alternating current; nuclear magnetic; surface water; ground surface; field applied; wire loops; position sensitivity; receiver antenna; diameter wire; phased array; underground nuclear; including oil; improved penetration; mineral deposit; active nuclei; active liquid; surface receive; /324/

Citation Formats

Stoeffl, Wolfgang. Use of earth field spin echo NMR to search for liquid minerals. United States: N. p., 2001. Web.
Stoeffl, Wolfgang. Use of earth field spin echo NMR to search for liquid minerals. United States.
Stoeffl, Wolfgang. Mon . "Use of earth field spin echo NMR to search for liquid minerals". United States. https://www.osti.gov/servlets/purl/873510.
@article{osti_873510,
title = {Use of earth field spin echo NMR to search for liquid minerals},
author = {Stoeffl, Wolfgang},
abstractNote = {An instrument for measuring the spatial, qualitative and quantitative parameters of an underground nuclear magnetic resonance (NMR) active liquid mineral deposit, including oil and water. A phased array of excitation and receiver antennas on the surface and/or in a borehole excites the NMR active nuclei in the deposit, and using known techniques from magnetic resonance imaging (MRI), the spatial and quantitative distribution of the deposit can be measured. A surface array may utilize, for example, four large (50-500 diameter) diameter wire loops laid on the ground surface, and a weak (1.5-2.5 kHz) alternating current (AC) field applied, matching the NMR frequency of hydrogen in the rather flat and uniform earth magnetic field. For a short duration (a few seconds) an additional gradient field can be generated, superimposed to the earth field, by applying direct current (DC) to the grid (wire loops), enhancing the position sensitivity of the spin-echo and also suppressing large surface water signals by shifting them to a different frequency. The surface coil excitation can be combined with downhole receivers, which are much more radio-quiet compared to surface receivers, and this combination also enhances the position resolution of the MRI significantly. A downhole receiver module, for example, may have a 5.5 inch diameter and fit in a standard six inch borehole having a one-quarter inch thick stainless steel casing. The receiver module may include more than one receiver units for improved penetration and better position resolution.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {1}
}

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