Feasibility of detecting artificial magnetic anomalies in hydrofractured rock by superconducting gradiometer-SQUID systems

Technical Report · Wed Dec 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7228213· OSTI ID:7228213

Overton, Jr, W C

A study of the signal physics of magnetic anomaly detection by superconducting gradiometer-SQUID systems to determine the feasibility of possible applications to the geothermal energy program is described. The system would make full use of the incredible sensitivity of the superconducting quantum interference device (SQUID) which can be in the range of 10/sup -11/ Oe. In addition to magnetic anomalies in the earth's field produced by spherical distributions of magnetic matter, anomalies that would be artificially produced by flooding magnetic material into cracks produced by hydrofracturing in deep boreholes drilled into dry rock geothermal sources are considered. The study indicates that surface detection by horizontal and vertical gradiometers of crack anomalies will not be feasible if the magnetic material flooding the crack is a paramagnetic solution. However, one can concoct a slurry to carry prepolarized ferromagnetic particles of a size sufficiently large to permit domain formation but small enough to permit rotation and alignment in the earth's field. In this case, the anomaly signal is large enough to permit extraction of anomaly orientation information out of the background of magnetic noise and earth's field gradients. The superconducting gradiometer-SQUID system is shown to be exceptional in its capability of removing undesirable magnetic noise and gradients. The greatest promise was found in systems that would be comprised of a magnetometer or gradiometer that could be lowered into the borehole to positions opposite the formations cracked by hydrofracturing. The use of a paramagnetic material to produce the artificial anomaly will not provide signals of sufficient amplitude to overcome the magnetic noise. However, the slurry containing only one percent by volume of ferromagnetic particles will produce a crack anomaly that is easily detectable by magnetometer or by the superconducting gradiometer-SQUID system.

• Research Organization: Los Alamos Scientific Lab., NM (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 7228213
• Report Number(s): LA-6626-MS
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150906* -- Geothermal Engineering-- Reservoir Stimulation & Extraction Technology
420201 -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOREHOLES
CAVITIES
COMMINUTION
DISPERSIONS
ELECTRONIC EQUIPMENT
FEASIBILITY STUDIES
FLUXMETERS
FRACTURING
GEOPHYSICAL SURVEYS
GEOTHERMAL SYSTEMS
Geothermal Legacy
HOT-DRY-ROCK SYSTEMS
HYDRAULIC FRACTURING
MAGNETIC FIELDS
MAGNETIC SURVEYS
MAGNETISM
MAGNETOMETERS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
MIXTURES
PARAMAGNETISM
POLARIZATION
ROCKS
SLURRIES
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUSPENSIONS