Directional resistivity measurements for azimuthal proximity detection of bed boundaries

An azimuthally tunable resistivity tool for use in a borehole having a borehole axis, wherein the tool comprises:

• at least three transmitter antennas configured to transmit a radio frequency signal, wherein the transmitter antennas are each oriented at a skew angle from the borehole axis, and wherein the transmitter antennas are oriented in differing azimuthal directions;
• and
• at least one receiver antenna configured to receive the radio-frequency signal.

A method for performing azimuthally tunable resistivity measurements, wherein the method comprises:

• transmitting an electromagnetic signal which propagates through a formation surrounding a borehole;
• measuring one or more characteristics of the electromagnetic signal using three skewed receiver antennas, wherein the skewed receiver antennas are oriented in equally spaced azimuthal directions;
• combining the skewed receiver measurements to form a desired virtual receiver measurement, wherein the desired virtual receiver has a desired skew angle and a desired azimuthal direction.

A method for performing azimuthally tunable resistivity measurements, wherein the method comprises:

• using three skewed transmitter antennas oriented in equally spaced azimuthal directions to transmit electromagnetic signals which propagate through a formation surrounding a borehole;
• using a receiver antenna to measure one or more characteristics of the electromagnetic signals;
• combining the measurements to form a receiver measurement of characteristics of electromagnetic signals transmitted by a desired virtual transmitter, wherein the desired virtual transmitter has a desired skew angle and a desired azimuthal direction.