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Macmillan Wisler Phones & Addresses

  • Lafayette, LA

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System For Monitoring Formation Spontaneous Potential And Polarization Constant While Drilling

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US Patent:
46251731, Nov 25, 1986
Filed:
Mar 30, 1984
Appl. No.:
6/595251
Inventors:
MacMillan M. Wisler - Lafayette LA
James R. Birchak - Spring TX
Richard A. Meador - Spring TX
Assignee:
NL Industries, Inc. - New York NY
International Classification:
G01V 300
G01V 308/3/18
US Classification:
324351
Abstract:
An electrode insulated from and mounted to the outside of a drill collar in a drill string positioned in a borehole is used for measuring formation spontaneous potential. A current measuring device, such as an ammeter, is connected through a varible ammeter resistor and a switch between the electrode and the drill collar. The ammeter measures current flow from the formation along the walls of the borehole to the drill string to determine the spontaneous potential of the formation at various points along the borehole while it is being drilled. The switch in the ammeter circuit is interrupted at a pre-selected rate and the ammeter current signal is connected through a lock-in amplifier to cancel random noise in the signal and produce an accurate measurement of the very small currents flowing between the electrode and the drill collar. The currents are indicative of spontaneous potentials in the formation. The value of the ammeter resistor is varied and the frequency of closure of the switch is swept over a pre-selected range to measure the time constant of the polarization of the formation along the borehole.

Electrical Resistivity Measurement Of A Flowing Drilling Fluid Using Eddy Currents Generated Therein

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US Patent:
45367132, Aug 20, 1985
Filed:
Mar 3, 1983
Appl. No.:
6/471879
Inventors:
Mark H. Davis - Spring TX
Richard A. Meador - Spring TX
Macmillan M. Wisler - Lafayette LA
Assignee:
NL Industries, Inc. - New York NY
International Classification:
G01V 326
G01N 2774
E21B 4900
US Classification:
324324
Abstract:
A high permeability ferrite core, which includes a gap between adjacent ends thereof, is combined with a magnetic coil encircling the core, and is located in a sub positioned in the drill string just above the drill bit of a borehole drilling rig. The core is positioned so that the gap thereof lies across a recess region formed in the outer wall of the sub. Drilling fluids flow along the outer surface of the sub on the return path from the drill bit to the mud pits located at the surface of the borehole. A constant current, or voltage, at a frequency within the range of 20 KHz-20 MHz is applied to the terminals of the coil encircling the core and the eddy currents developed in the gap region produce a measurable back emf at the coil terminals. The current produced by this emf voltage is indicative of the resistivity of the drilling fluid within the recess region in the wall of the sub and the fluctuations of the voltage accurately follow the variations in drilling fluid resistivity.
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