Methods and apparatus for measurement of the resistivity of geological formations from within cased boreholes
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. 3 figs.
- DOE Contract Number:
- FG06-84ER13294
- Assignee:
- ParaMagnetic Logging, Inc., Woodinville, WA (United States)
- Patent Number(s):
- US 4820989; A
- Application Number:
- PPN: US 6-927115
- OSTI ID:
- 7164630
- Resource Relation:
- Patent File Date: 4 Nov 1986
- Country of Publication:
- United States
- Language:
- English
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