Electricity: measuring and testing – Of geophysical surface or subsurface in situ – With radiant energy or nonconductive-type transmitter
Patent
1997-07-01
2000-11-14
Snow, Walter E.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
With radiant energy or nonconductive-type transmitter
702 7, G01V 310, G01V 318, G01V 328, G06F 1900
Patent
active
061474967
ABSTRACT:
A method is provided for determining an electric conductivity of an earth formation formed of different earth layers, which earth formation is penetrated by a wellbore containing a wellbore fluid, is provided. The method includes the steps of: lowering an induction logging tool into the wellbore to a location surrounded by a selected one of the earth layers, the tool having a magnetic field transmitter effective to induce magnetic fields of different frequencies in the earth formation, and a magnetic field receiver effective to receive response magnetic fields and to provide a signal representative of each response magnetic field, at least one of the transmitter and the receiver having a plurality of magnetic dipole moments in mutually orthogonal directions. At least two of the different frequencies are selected, and for each selected frequency, the transmitter is operated so as to induce a magnetic field in the earth formation and the receiver is operated so as to provide a signal representing a response magnetic field, wherein the at least one of the transmitter and receiver is operated in the mutually orthogonal directions. The signals are combined in a manner so as to create a combined signal having a reduced dependency on the electric conductivity in the wellbore region. The formation resistivity and the relative orientation of the logging tool with respect to the formation layering is determined from the combined signal.
REFERENCES:
patent: 3808520 (1974-04-01), Runge
patent: 4972150 (1990-11-01), Tabbagh
patent: 5781436 (1998-07-01), Forgang et al.
Bear David Ronald
Strack Kurt-Martin
Tabarovsky Leonty Abraham
Van Der Horst Melis
Shell Oil Company
Snow Walter E.
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