Method for radial profiling of resistivity at multiple depths of investigation
AssigneeHalliburton Energy Services, Inc.
InventorTeruhiko Hagiwara
Life of this patent
Estimating the term…
Abstract
A resistivity tool suitable for use in a borehole and configured to obtain a resistivity radial profile at multiple depths of investigation in a geological formation comprises a receiver pair and an array of transmitters. The distance of each transmitter from the receivers corresponds to a particular depth of investigation into the formation. Using as few as two transmitters, the resistivity tool derives resistivity values at any number of depths of investigation, including depths of investigation that do not correspond to transmitter/receiver spacings on the tool. A measurement processor combines signals received from the existing transmitters using linear interpolation, geometric interpolation, and/or other techniques to derive the resistivity measurements.
Claims48
A method for profiling resistivity in a borehole at multiple depths of investigation, comprising:
- receiving, by each receiver of a receiver pair, a first electromagnetic wave transmitted by a first transmitter, wherein the distance between said receiver pair and said first transmitter corresponds to a first depth of investigation;
- receiving, by each receiver of the receiver pair, a second electromagnetic wave transmitted by a second transmitter, wherein the distance between said receiver pair and said second transmitter corresponds to a second depth of investigation;
- combing outputs from the receiver pair associated with the first and second electromagnetic waves to calculate a resistivity value corresponding to a third depth of investigation, wherein the third depth of investigation is different than the first and second depths of investigation.
A method for profiling resistivity in a borehole, comprising:
- locating a first transmitter at a first distance from a receiver pair;
- locating a second transmitter at a second distance from the receiver pair;
- choosing a third distance from said receiver pair that is different than the first and second distances;
- measuring a first complex envelope of a signal transmitted form the first transmitter and received by the receiver pair;
- measuring a second complex envelope of a signal transmitted from the second transmitter and received by the receiver pair;
- and
- deriving a resistivity based on the first and second complex envelopes, wherein the depth of investigation of the derived resistivity corresponds to a transmitter to receiver spacing equal to the third distance.
A tool for measuring resistivity, comprising:
- a first receiver pair mounted on said tool;
- a first transmitter mounted on said tool that propagates a first signal to said first receiver pair over a first distance spanning the first receiver pair and the first transmitter, the first distance corresponding to a first depth of investigation;
- a second transmitter mounted on said tool that propagates a second signal to said first receiver pair over a second distance spanning the first receiver pair and the second transmitter, the second distance corresponding to a second depth of investigation;
- and
- a measurement processor coupled to said first receiver pair, wherein said measurement processor combines outputs from the first receiver pair associated with the first and second signals to calculate a resistivity corresponding to a third depth of investigation, wherein the first, second, and third depths of investigation comprise different depths of investigation.
A compensated resistivity tool, comprising:
- a first electromagnetic signal receiver;
- a second electromagnetic signal receiver;
- a first main transmitter located at a first distance above a center point between said first receiver and said second receiver, said first main transmitter capable of transmitting electromagnetic signals to said first and second receivers;
- a first compensating transmitter located at the first distance below the center point, said first compensating transmitter capable of transmitting electromagnetic signals to said first and second receivers;
- a second main transmitter located at a second distance above the center point, said second main transmitter capable of transmitting electromagnetic signals to said first and second receivers, wherein the second distance is smaller than the first distance;
- a second compensating transmitter located at the second distance below the center point, said second compensating transmitter capable of transmitting electromagnetic signals to said first and second receivers;
- and
- a processor coupled to said first and second receivers, said processor determines a formation resistivity based on said electromagnetic signals and corresponding to a depth of investigation as a function of a third distance from the center point, wherein the third distance from the center point corresponds to a location at which said resistivity tool does not include a transmitter.
Dependencies are inferred from the claim text.