Abstract: Methods capable of determining a depth of investigation of a logging tool can include generating an error distribution model for a logging tool. The methods can also include defining a detection threshold above which a measured signal from a measurement channel of the logging tool can be considered reliable based on output from the error distribution model, and generating a simulated formation model to determine the depth of investigation. The depth of investigation can be biased by the detection threshold.

Abstract: A method for making downhole electromagnetic logging measurements of a subterranean formation is disclosed. An electromagnetic logging tool is rotated in a subterranean wellbore. The tool includes a transmitter axially spaced apart from a receiver. The transmitter may include an axial transmitting antenna and at least one transverse transmitting antenna and the receiver may include an axial receiving antenna and at least one transverse receiving antenna. The transmitting antennas transmit corresponding electromagnetic waves into the subterranean wellbore. The receiving antennas receive corresponding voltage measurements which are processed to compute harmonic voltage coefficients. Ratios of the selected harmonic voltage coefficients are processed to compute gain compensated, azimuthally invariant measurement quantities.

Abstract: A method for making gain compensated electromagnetic logging measurements of a subterranean formation includes rotating an electromagnetic logging tool in a subterranean wellbore. The logging tool includes a transmitter having at least one transmitting antenna axially spaced apart from a receiver having at least one receiving antenna. Electromagnetic waves are transmitted into the subterranean wellbore using the at least one transmitting antenna. Voltage measurements corresponding to the transmitted electromagnetic waves are received at the receiving antenna. The voltage measurements are processed to compute real and imaginary directional resistivity measurement quantities.

Abstract: A method for making downhole electromagnetic logging measurements includes using an electromagnetic measurement tool to acquire the measurements while rotating in a subterranean wellbore. Received electromagnetic waves are processed to obtain harmonic voltage coefficients, ratios of which are in turn further processed to compute gain compensated measurement quantities. The gain compensated measurement quantities are further processed to compute at least one of an apparent formation azimuth of the formation through which the wellbore traverses, an apparent tool eccentering azimuth, and an eccentering distance of the logging tool in the wellbore.

Abstract: A logging tool having a plurality of spatially separated antennas is provided and used to make propagation-style measurements in a formation. Tensors are formed using the propagation-style measurements and one or more quantities are computed using the tensors. A formation evaluation is performed using the computed quantities. The formation evaluation determines a formation property or parameter such as horizontal resistivity, vertical resistivity, relative dip, azimuthal dip, bed boundary location, or bed thickness. The computed quantities may include compensated phase shift resistivity, compensated attenuation resistivity, symmetrized phase shift resistivity, symmetrized attenuation resistivity, anti-symmetrized phase shift resistivity, and anti-symmetrized attenuation resistivity. The measurements may be corrected for antenna gain errors and an air calibration may be performed.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging while drilling tool includes at least first and second tilted transmitter antennas longitudinally spaced along a logging while drilling tool body and at least first and second tilted receiver antennas. A plurality of electromagnetic voltage measurements is acquired at the first and second tilted receiver antennas while rotating and processed to compute harmonic voltage coefficient. Ratios of selected ones of the harmonic voltage coefficients are then processed to compute at least one gain compensated measurement quantity.

Abstract: An arrangement for generating a resistivity image having a drill bit with cutters configured to be placed within a wellbore, the cutters configured to create further sections of the wellbore upon rotation, the drill bit having an end with threads for engagement, at least one section of drill string connected to the drill bit through a matching set of threads for engagement, a receiver toroid connected to the at least one section of drill string along at least a portion of the drill string, a transmitter toroid connected to the at least one section of drill string and located at least a portion of the drill string away from the receiver toroid, at least one stabilizer connected to the at least one section of drill string, a power source connected to the transmitter toroid and the receiver toroid, an electrode arrangement placed at the drill bit, wherein the electrode arrangement is electrically connected to the drill bit through a non-linear circuit element and a computer arrangement connected to the receiver

Abstract: A drill string can include an electromagnetic transmitter oriented at an actual effective tilt angle with respect to the drill string and an electromagnetic receiver oriented at an actual effective tilt angle with respect to the drill string. The transmitter and received can be used to investigate geologic formations surrounding the drill string, and measurements of the geologic formations can be based on the actual effective tilt angles of the transmitter and the receiver.

Abstract: A method for making downhole electromagnetic logging measurements of a subterranean formation is disclosed. An electromagnetic logging tool is rotated in a subterranean wellbore. The tool includes a transmitter axially spaced apart from a receiver. The transmitter may include an axial transmitting antenna and at least one transverse transmitting antenna and the receiver may include an axial receiving antenna and at least one transverse receiving antenna. The transmitting antennas transmit corresponding electromagnetic waves into the subterranean wellbore. The receiving antennas receive corresponding voltage measurements which are processed to compute harmonic voltage coefficients. Ratios of the selected harmonic voltage coefficients are processed to compute gain compensated, azimuthally invariant measurement quantities.

Abstract: A method for making gain compensated electromagnetic logging measurements of a subterranean formation includes rotating an electromagnetic logging tool in a subterranean wellbore. The logging tool includes a transmitter having at least one transmitting antenna axially spaced apart from a receiver having at least one receiving antenna. Electromagnetic waves are transmitted into the subterranean wellbore using the at least one transmitting antenna. Voltage measurements corresponding to the transmitted electromagnetic waves are received at the receiving antenna. The voltage measurements are processed to compute real and imaginary directional resistivity measurement quantities.

Abstract: Methods capable of determining a depth of investigation of a logging tool can include generating an error distribution model for a logging tool. The methods can also include defining a detection threshold above which a measured signal from a measurement channel of the logging tool can be considered reliable based on output from the error distribution model, and generating a simulated formation model to determine the depth of investigation. The depth of investigation can be biased by the detection threshold.

Abstract: An arrangement for generating a resistivity image having a drill bit with cutters configured to be placed within a wellbore, the cutters configured to create further sections of the wellbore upon rotation, the drill bit having an end with threads for engagement, at least one section of drill string connected to the drill bit through a matching set of threads for engagement, a receiver toroid connected to the at least one section of drill string along at least a portion of the drill string, a transmitter toroid connected to the at least one section of drill string and located at least a portion of the drill string away from the receiver toroid, at least one stabilizer connected to the at least one section of drill string, a power source connected to the transmitter toroid and the receiver toroid, an electrode arrangement placed at the drill bit, wherein the electrode arrangement is electrically connected to the drill bit through a non-linear circuit element and a computer arrangement connected to the receiver

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging tool includes first and second transmitters, each of which includes a tilted antenna, and a receiver axially spaced apart from one another. Electromagnetic voltage measurements are made at the receiver while the tilted transmitting antenna in the first transmitter fires during tool rotation. The electromagnetic voltage measurements are mathematically rotated through at least the arbitrary angle to obtain rotated measurements, selected ratios of which are processing to compute gain compensated measurement quantities.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging tool includes a plurality of transmitter antennas and a plurality of receiver antennas symmetrically spaced along a logging while drilling tool body, the plurality of transmitter antennas including at least one axial transmitter antenna and at least one transverse transmitter antenna. The plurality of receiver antennas includes at least one axial receiver antenna and at least one transverse receiver antenna. The receiver antennas are used to acquire electromagnetic voltage measurements while rotating. The voltage measurements are processed to compute harmonic voltage coefficients, selected ratios of which are processed to compute gain compensated symmetrized and anti-symmetrized quantities and angles.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging while drilling tool includes at least first and second tilted transmitter antennas longitudinally spaced along a logging while drilling tool body and at least first and second tilted receiver antennas. A plurality of electromagnetic voltage measurements is acquired at the first and second tilted receiver antennas while rotating and processed to compute harmonic voltage coefficient. Ratios of selected ones of the harmonic voltage coefficients are then processed to compute at least one gain compensated measurement quantity.

Abstract: A method for making downhole electromagnetic logging measurements includes using an electromagnetic measurement tool to acquire the measurements while rotating in a subterranean wellbore. Received electromagnetic waves are processed to obtain harmonic voltage coefficients, ratios of which are in turn further processed to compute gain compensated measurement quantities. The gain compensated measurement quantities are further processed to compute at least one of an apparent formation azimuth of the formation through which the wellbore traverses, an apparent tool eccentering azimuth, and an eccentering distance of the logging tool in the wellbore.

Abstract: An electromagnetic well logging instrument includes an instrument housing, at least one transmitter coil disposed on the housing and at least one receiver coil disposed on the housing. At least one of the transmitter and receiver coils is formed from a combination solenoidal (axial) and saddle coils. The net dipole moment direction of the combined coil is determined by selecting the relative turn-areas of the saddle and solenoidal coil. The combined coil can be formed from a single wire wound to have both a longitudinal magnetic dipole moment and a transverse magnetic dipole moment with respect to a longitudinal axis of the housing.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging tool includes first and second transmitters, each of which includes a tilted antenna, and a receiver axially spaced apart from one another. Electromagnetic voltage measurements are made at the receiver while the tilted transmitting antenna in the first transmitter fires during tool rotation. The electromagnetic voltage measurements are mathematically rotated through at least the arbitrary angle to obtain rotated measurements, selected ratios of which are processing to compute gain compensated measurement quantities.

Abstract: A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging tool includes a plurality of transmitter antennas and a plurality of receiver antennas symmetrically spaced along a logging while drilling tool body, the plurality of transmitter antennas including at least one axial transmitter antenna and at least one transverse transmitter antenna. The plurality of receiver antennas includes at least one axial receiver antenna and at least one transverse receiver antenna. The receiver antennas are used to acquire electromagnetic voltage measurements while rotating. The voltage measurements are processed to compute harmonic voltage coefficients, selected ratios of which are processed to compute gain compensated symmetrized and anti-symmetrized quantities and angles.

Abstract: A method detects at least one phase of multiphase borehole fluids within a borehole. The method has a step of providing coiled tubing connected to a top end of a bottom hole assembly having a sensor configured to detect a property associated with the multiphase borehole fluids. Further, the method has a step of positioning the sensor adjacent to a first phase of the multiphase borehole fluids by rotating the bottom hole assembly or a portion of the bottom hole assembly. Moreover, the method has the steps of detecting a first measurement with the sensor as the sensor rotates and determining a fractional amount of at least one phase of the multiphase borehole fluids.