Atlantic Richfield Company

James D Klein

Michael F Gard

Brian R Spies

John E Kingman

Gary Lee White

Mark H Scheihing

A method for determining a relative clay content of at least a portion of a well core taken from a subterranean geologic formation by: determining the relationship of the clay content of the well core portion to the dielectric constant of the well core portion at a selected frequency at relatively few locations over a substantial length of the well core portion by measuring the clay content by a clay determination test such as x-ray diffraction, thin section analysis, sieve analysis or laser particle analysis and the dielectric constant at the locations; and, measuring the dielectric constant of the well core portion at a large plurality of spaced apart other locations on the well core portion at the selected frequency; translating the large plurality of dielectric measurements according to the relationship into relative clay content measurements. The dielectric constant is representative of the water constant of the well core portion, which is related to the clay content of the well core portion.

Method for determining the relative clay content of well core

A method of locating thin bed hydrocarbon reserves in laminated subterranean formations comprising thin beds. The method comprised of drilling a well penetrating the subterranean formations, measuring the parallel and perpendicular resistivity across multiple thin beds, and locating regions of the thin beds where the perpendicular resistivity is substantially greater than the parallel resistivity.

Method for locating thin bed hydrocarbon reserves utilizing electrical

A borehole telemetry system has a transmitter located in the borehole, a surface receiver, and surface signal sensors for receiving the transmitted signal. There are usually plural sources of electromagnetic noise at a well site which degrade the usefulness of the telemetry system. The method places noise sensors where the reception of noise is maximized. Simultaneous measurements are taken of the ambient noise with the noise sensors and the signal sensors. The relationship between the measurements of the noise and signal sensors is determined. The transmitted signal is then received by the signal sensors and simultaneous measurements of the ambient noise are made by the noise sensors. The noise portion of the transmitted signal as received by the signal sensors is determined from the simultaneous noise measurements and the determined relationship. A received signal having reduced noise is then produced by removing the noise portion.

Method of reducing noise in a borehole electromagnetic telemetry system

The resistivity of a geologic formation is measure through drillpipe or casing by applying a low frequency bipolar voltage to the casing and to a ground electrode and traversing the casing with a tool having contractors which are connected to a differential amplifier to detect a differential voltage within the casing caused by current leaving the casing into the formation. The differential amplifier is connected to a unity gain inverter and a switching arrangement for alternately reversing the polarity of the connection of input voltages to the differential amplifier. A switching network alternately connects the outputs of the differential amplifier and the output of the inverter to the input of a low pass filter, and a clock is provided for driving the network in synchronization. The casing and formation resistivities may be measured by applying a voltage along a predetermined length of casing between two contractors which are spaced apart farther and on opposite sides of the differential amplifier pickup contactors. The voltage applied across the formation may be applied to the casing at the earth's surface or downhole adjacent the points of measurement of casing resistivity and formation resistivity.

Method and apparatus for measuring the electrical resistivity of

An improved method and apparatus for detecting telluric noise information while performing induced polarization prospecting. Telluric noise electrodes are positioned on an equipotential line lying about an input current electrode forming part of a conventional IP electrode spread. The telluric noise record obtained from the noise electrodes is essentially free of IP input signal waveform.

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Lucas, TX, United States of America

James D Klein