Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Patent
1989-05-24
1991-09-17
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
324374, G01V 320
Patent
active
050498223
ABSTRACT:
A microelectric method and apparatus for recording and differentiating between open and closed fractures along the walls of boreholes is disclosed. A main current and a controlled opposing or bucking current are fed into a hard rock formation in a measurement area of a borehole wall insulated from the drilling mud in the borehole. Within this measurement area absolute potential and potential differences are measured and dimensionless ratios based on the measurements of current and potential are ascertained. The ratios indicate the presence of fractures and allow differentiation between open and closed fractures allowing determination of an open fracture network. The apparatus is made up of at least one measuring pad (6) made of insulating material forced onto the wall of borehole. The measuring pad (6) includes a central measuring electrode (14), a ring shaped outer measuring electrode (13), both connected to potential measuring units (22, 23), and surrounded by a first feeding electrode (9) which is connected to a main current generator (15), two monitoring electrodes (11, 12) connected to the input of a controlled current generator (16) for regulating the bucking current supplied by the second feeding electrode (10) surrounding the monitoring and the first feeding electrodes.
REFERENCES:
patent: 2880389 (1959-03-01), Ferre et al.
patent: 2961600 (1960-11-01), Tanguy
patent: 3798535 (1974-03-01), Schuster
patent: 4282486 (1981-08-01), Culver et al.
Attila Vamos
Ferenc Rez
Geza Dorcsi
Peter Ribiczey
Zoltan Barlai
Edmonds Warren S.
Eisenzopf Reinhard J.
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