Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Patent
1981-07-30
1984-08-28
Strecker, Gerard R.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
324355, 324374, G01V 320
Patent
active
044686234
ABSTRACT:
Methods and apparatuses for electrically investigating a borehole are described. Tool mounted pads are provided, each with a plurality of small measure electrodes from which individually measurable survey currents are injected toward the wall of the borehole. The measure electrodes are arranged in an array in which the measure electrodes are so placed at intervals along at least a circumferential direction (about the borehole axis) as to inject survey currents into the borehole wall segments which overlap with each other to a predetermined extent as the tool is moved along the borehole. The measure electrodes are made small to enable a detailed electrical investigation over a circumferentially contiguous segment of the borehole so as to obtain indications of the stratigraphy of the formation near the borehole wall as well as fractures and their orientations. In one technique, a spatially closed loop array of measure electrodes is provided around a central electrode with the array used to detect the spatial pattern of electrical energy injected by the central electrode. In another embodiment, a linear array of measure electrodes is provided to inject a flow of current into the formation over a circumferentially effectively contiguous segment of the borehole. Discrete portions of the flow of current are separably measurable so as to obtain a plurality of survey signals representative of the current density from the array and from which a detailed electrical picture of a circumferentially continuous segment of the borehole wall can be derived as the tool is moved along the borehole. In another form of an array of measure electrodes, they are arranged in a closed loop, such as a circle, to enable direct measurements of orientations of resistivity of anomalies.
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Article--"Reservoir Evaluation of Fractured Cretaceous Carbonates in South Texas", J. Beck, A. Schultz, D. Fitzgerald-SPWLA, Eighteenth Annual Logging Symposium, Jun. 5-8, 1977.
Article--"The High Resolution Dipmeter Tool", L. A. Allaud and J. Ringot, reprinted from The Log Analyst, May-Jun., 1969.
Chan David S. K.
Gianzero Stanley C.
Palaith David E.
Borst Stephen L.
Carroll David H.
Reens Louis H.
Schlumberger Technology Corporation
Strecker Gerard R.
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