Methods to configure a downhole electromagnetic tool and downhole electromagnetic tool calibration systems are disclosed. A method to configure a downhole electromagnetic tool includes obtaining a first calibration measurement of a first tool configuration and a second calibration measurement of a second tool configuration of a downhole electromagnetic tool, and determining a first ratio of the first calibration to the second calibration. The method further includes obtaining a first synthetic response of the first tool configuration from a first model of the downhole electromagnetic tool, and obtaining a second synthetic response of the second tool configuration from a second model of the downhole electromagnetic tool, and determining a second ratio of the first synthetic response to the second synthetic response. The method further includes determining a scaling factor between the first tool configuration and the second tool configuration of the downhole electromagnetic tool based on the first and second ratios.

Methods to configure a downhole electromagnetic tool and downhole electromagnetic tool calibration systems are disclosed. A method to configure a downhole electromagnetic tool includes obtaining a first calibration measurement of a first tool configuration and a second calibration measurement of a second tool configuration of a downhole electromagnetic tool, and determining a first ratio of the first calibration to the second calibration. The method further includes obtaining a first synthetic response of the first tool configuration from a first model of the downhole electromagnetic tool, and obtaining a second synthetic response of the second tool configuration from a second model of the downhole electromagnetic tool, and determining a second ratio of the first synthetic response to the second synthetic response. The method further includes determining a scaling factor between the first tool configuration and the second tool configuration of the downhole electromagnetic tool based on the first and second ratios.

Certain aspects of the present disclosure relate to calibrating a formation signal for a mixed set measurement device. A first air-hang response of a first measurement device for a tubular string associated with a drilling operation can be measured. A second air-hang response of a second measurement device for the tubular string associated with the drilling operation can be measured. The first air-hang response and the second air-hang response can be used to determine a mixed air-hang response of the mixed set measurement device. The mixed air-hang response can be used to calibrate a formation signal for the mixed set measurement device.

Embodiments relate generally to marine geophysical surveying. More particularly, embodiments relate to an underwater application system for application of a streamer coating to a surface of a streamer. An embodiment may comprise a marine geophysical survey system. The marine geophysical survey system may comprise a streamer and an underwater application system operable to apply a streamer coating to the streamer as the underwater application system travels axially along the streamer.

A method for making calibrated directional electromagnetic logging measurements includes causing an electromagnetic logging tool to make a plurality of voltage measurements while deployed in a subterranean wellbore. A ratio of currents in first and second electromagnetic transmitters is computed and a ratio of gains in first and second electromagnetic receivers is computed. A ratio of selected ones of the measured voltages is processed in combination with the ratio of currents, the ratio of gains, and a test loop calibration coefficient to compute the calibrated directional electromagnetic logging measurement.

A method for making calibrated directional electromagnetic logging measurements includes causing an electromagnetic logging tool to make a plurality of voltage measurements while deployed in a subterranean wellbore. A ratio of currents in first and second electromagnetic transmitters is computed and a ratio of gains in first and second electromagnetic receivers is computed. A ratio of selected ones of the measured voltages is processed in combination with the ratio of currents, the ratio of gains, and a test loop calibration coefficient to compute the calibrated directional electromagnetic logging measurement.

A method and apparatus to calibrate a resistivity measurement taken by a downhole tool in a borehole, wherein the downhole tool estimates the resistivity of an underground formation penetrated by the borehole with at least one sensor situated at a non-zero standoff distance from the borehole, is provided. The method includes taking apparent impedance measurements with the sensor at a set of frequencies and at a first plurality of locations in the borehole, wherein the measurement are uncalibrated measurements. The method also includes identifying a portion of the borehole in which the apparent impedance measurements at least at a first frequency of the set have a predetermined behavior. The predetermined behavior is that the apparent impedance measurements taken in the portion are substantially fitting a linear model when represented in the complex plane. The method also includes using a plurality of measurements obtained at a second plurality of location situated in said portion at the first frequency to determine calibration coefficients for the measurements at said frequency.

A method and apparatus to calibrate a resistivity measurement taken by a downhole tool in a borehole, wherein the downhole tool estimates the resistivity of an underground formation penetrated by the borehole with at least one sensor situated at a non-zero standoff distance from the borehole, is provided. The method includes taking apparent impedance measurements with the sensor at a set of frequencies and at a first plurality of locations in the borehole, wherein the measurement are uncalibrated measurements. The method also includes identifying a portion of the borehole in which the apparent impedance measurements at least at a first frequency of the set have a predetermined behavior. The predetermined behavior is that the apparent impedance measurements taken in the portion are substantially fitting a linear model when represented in the complex plane. The method also includes using a plurality of measurements obtained at a second plurality of location situated in said portion at the first frequency to determine calibration coefficients for the measurements at said frequency.

Systems, apparatuses, and method of measuring hydrophone impedance are provided herein. A sensor can convert an acoustic wave received via a liquid medium into an electric signal. A signal encoder can be coupled with the sensor to receive the electric signal. A test signal generator can be coupled in series with the sensor and the signal encoder and can generate a test signal. The test signal can measure an impedance of the sensor. A switch component can be coupled in series with the sensor, the signal encoder, and the test signal generator. The switch component can route the test signal to a first terminal of the sensor and through a second terminal of sensor during a first operational state. The switch component can route the test signal to the second terminal of the sensor and through the first terminal of sensor during a second operational state.

Systems, apparatuses, and method of measuring hydrophone impedance are provided herein. A sensor can convert an acoustic wave received via a liquid medium into an electric signal. A signal encoder can be coupled with the sensor to receive the electric signal. A test signal generator can be coupled in series with the sensor and the signal encoder and can generate a test signal. The test signal can measure an impedance of the sensor. A switch component can be coupled in series with the sensor, the signal encoder, and the test signal generator. The switch component can route the test signal to a first terminal of the sensor and through a second terminal of sensor during a first operational state. The switch component can route the test signal to the second terminal of the sensor and through the first terminal of sensor during a second operational state.