Methods and apparatus for measurement of the resistivity of geological formations from within cased boreholes

Patent · Sun Jan 01 00:00:00 EST 1989

OSTI ID:866915

Vail, III, William B. ^[1]

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1. (Bothell, WA)

Methods and apparatus are disclosed which allow measurement of the resistivity of a geological formation through borehole casing which may be surrounded by brine saturated cement. A.C. current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. The A.C. voltage difference is measured between two additional vertically disposed electrodes on the interior of the casing which provides a measure of the resistivity of the geological formation. A calibration and nulling procedure is presented which minimizes the influence of variations in the thickness of the casing. The procedure also minimizes the influence of inaccurate placements of the additional vertically disposed electrodes.

• Research Organization: ParaMagnetic Logging, Inc. (Bothell, WA)
• DOE Contract Number: FG06-84ER13294
• Assignee: ParaMagnetic Logging, Inc. (Woodinville, WA)
• Patent Number(s): US 4820989
• OSTI ID: 866915
• Country of Publication: United States
• Language: English

Related Subjects

methods
apparatus
measurement
resistivity
geological
formations
cased
boreholes
disclosed
allow
formation
borehole
casing
surrounded
brine
saturated
cement
current
passed
electrode
electrical
contact
interior
surface
earth
voltage
difference
measured
additional
vertically
disposed
electrodes
provides
measure
calibration
nulling
procedure
minimizes
influence
variations
thickness
inaccurate
placements
vertically disposed
geological formations
electrical contact
cased boreholes
borehole casing
geological formation
voltage difference
cased borehole
allow measurement
cased bore
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