Electricity: measuring and testing – Of geophysical surface or subsurface in situ – With radiant energy or nonconductive-type transmitter
Patent
1981-08-19
1984-11-06
Strecker, Gerard R.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
With radiant energy or nonconductive-type transmitter
G01V 328
Patent
active
044814720
ABSTRACT:
An apparatus and method for measuring properties of earth formations surrounding a borehole and, particularly, conductivity properties of the formations and certain properties of the invaded zone of the formations. In accordance with one embodiment of the invention, a logging device, movable through the borehole, has a transmitter coil and first and second spaced receiver coils mounted thereon. A short pulse of electrical energy is applied to the transmitter coil. Signals are induced in the first and second receiver coils. A conductivity property of the surrounding formations is then determined as a function of the times of occurrence of predetermined characteristics of the signals detected in the first and second receiver coils. In particular, the elapsed time between a zero-crossing of the signal induced in the first receiver coil and a zero-crossing of the signal induced in the second receiver coil is measured, and the conductivity of the surrounding formations is determined as being substantially proportional to said elapsed time. In another embodiment of the invention the polarities of the initial portions of the signals detected at a number of receiver locations are used in determining properties of the formation invaded zone, particularly its thickness and its conductivity as compared to the virgin formations.
REFERENCES:
patent: 3090910 (1963-05-01), Moran
patent: 3849721 (1974-11-01), Calvert
patent: 4100483 (1978-07-01), Thompson et al.
patent: 4130793 (1978-12-01), Bridges et al.
Carroll David
Edmonds Warren S.
Novack Martin
Schlumberger Technology Corporation
Strecker Gerard R.
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