Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Patent
1995-08-21
2000-02-08
Snow, Walter E.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
324366, G01V 320
Patent
active
060231688
ABSTRACT:
A method for measuring formation resistivity uses a tool including a central current electrode and a series of voltage electrodes arranged in pairs on either side of the current electrode. A series of measurements is made using the current electrode with different numbers of pairs of voltage electrodes maintained at a predetermined voltage so as to allow resistivity in the formation to be determined with different depths of investigation. In this manner these measurements are focused and are relatively unaffected by the borehole or by adjacent layers in the formation. The central current electrode is segmented azimuthally into a series of electrodes, and the current flowing out of each azimuthal segment is measured separately. This can yield resistivity images of the formation surrounding the borehole. The azimuthal imaging capability can be used for stratigraphic or lithologic analysis of the formation and to detect fractures in the rock. The three-dimensional imaging capability can be used in deviated wells or horizontal wells to detect asymmetric invasion, or to locate a bed boundary close to the borehole.
REFERENCES:
patent: 3256480 (1966-06-01), Runge et al.
patent: 3262050 (1966-07-01), Threadgold et al.
patent: 3772589 (1973-11-01), Scholberg
patent: 4675610 (1987-06-01), Chapman et al.
patent: 4675611 (1987-06-01), Chapman et al.
patent: 4677385 (1987-06-01), Chapman et al.
patent: 4677386 (1987-06-01), Chapman et al.
patent: 5210691 (1993-05-01), Freedman et al.
patent: 5343153 (1994-08-01), Davies et al.
D. V. Ellis, "Well Logging for Earth Scientists", Elsevier, 1987, pp. 84-97, is cited in the specification and describes a laterolog technique which comprises making a measurement with a tool having a current emitting electrode and voltage electrodes on either side thereof which are operated to force current into the formation.
H. G. Doll, "The Laterolog: A New Resistivity Logging Method with Electrodes Using an Automatic Focusing System", Petroleum Transactions, AIME, vol. 192, 1951, pp. 305-316 is cited in the specification and describes the simplest laterolog electrode tool--the Laterolog-3.
Batzer William B.
Schlumberger Technology Corporation
Snow Walter E.
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