Electronic measurement apparatus movable in a cased borehole and compensating for casing resistance differences
Methods of operation are described for an apparatus having at least two pairs of voltage measurement electrodes vertically disposed in a cased well to measure the resistivity of adjacent geological formations from inside the cased well. During stationary measurements with the apparatus at a fixed vertical depth within the cased well, the invention herein discloses methods of operation which include a measurement step and subsequent first and second compensation steps respectively resulting in improved accuracy of measurement. The invention also discloses multiple frequency methods of operation resulting in improved accuracy of measurement while the apparatus is simultaneously moved vertically in the cased well. The multiple frequency methods of operation disclose a first A.C. current having a first frequency that is conducted from the casing into formation and a second A.C. current having a second frequency that is conducted along the casing. The multiple frequency methods of operation simultaneously provide the measurement step and two compensation steps necessary to acquire accurate results while the apparatus is moved vertically in the cased well. 6 figures.
- Research Organization:
- Paramagnetic Logging Inc
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG22-88BC14243
- Assignee:
- ParaMagnetic Logging, Inc., Woodinville, WA (United States)
- Patent Number(s):
- US 5075626; A
- Application Number:
- CNN: 5088-212-1664; PPN: US 7-434886
- OSTI ID:
- 7027207
- Resource Relation:
- Patent File Date: 13 Nov 1989
- Country of Publication:
- United States
- Language:
- English
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