Formation resistivity measurements using multiple controlled modes

摘要

Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole. The apparatus includes a plurality of electrodes disposed downhole and configured to inject an electrical current into the earth formation using an applied voltage and/or measure electrical current resulting from an injection of the electrical current. The apparatus also includes a processor configured to perform a series of formation measurements that include injecting current into the earth formation using a unique subset of electrodes in the plurality of electrodes and measuring current in the earth formation using one or more electrodes not used for the current injecting. The processer sums the measured currents for the electrodes wherein the sum of electrical currents for at least one electrode that measured electrical current is substantially in phase with the applied voltage; and uses the sum of in phase currents to estimate the property.

主权项

1. An apparatus for estimating a property of an earth formation penetrated by a borehole, the apparatus comprising:
a carrier configured to be conveyed through the borehole; a plurality of electrodes disposed at the carrier and configured to inject an electrical current into the earth formation using an applied voltage and/or measure electrical current resulting from an injection of the electrical current; and a processor configured to:
perform a series of formation measurements, each formation measurement comprising:
injecting electrical current into the earth formation using a unique subset of electrodes in the plurality of electrodes; andmeasuring electrical current in the earth formation using one or more electrodes in the plurality of electrodes not used for the injecting electrical current in the formation measurement;sum the electrical currents measured for each electrode that measured electrical current for the series of formation measurements wherein the sum of electrical currents for at least one electrode that measured electrical current is substantially in phase with the applied voltage; anduse the sum of electrical currents that are substantially in phase with the applied voltage to estimate the property.