Abstract: Systems, methods, and devices for compensating for environmental conditions on electromagnetic measurements are provided. For example, a downhole logging tool may include a first transmitter coil, a second transmitter coil, and a first receiver coil. The first transmitter coil may provide a first magnetic signal in a wellbore having a conductive casing. The second transmitter coil may provide a second magnetic signal in the wellbore. The first receiver may obtain a first measurement relating to the first magnetic signal and a second measurement relating to the second magnetic signal. The first receiver coil may be near enough to the first transmitter coil and the second transmitter coil to obtain measurements predominantly in the near field eddy current regime. A ratio of the first measurement and the second measurement may cancel environmental dependencies of the first receiver coil.

Abstract: A surface seismic survey is generated or obtained from Earth's surface and is based on time in which acoustic waves are reflected to Earth's surface. One or more tools measure density and sonic velocity of a subsurface formation. An estimate of acoustic impedance is obtained from the density and the sonic velocity to generate a synthetic seismic survey. The synthetic seismic survey and the surface seismic survey are compared and/or correlated. The acoustic impedance can be iteratively estimated until the synthetic seismic survey matches the surface seismic survey. Matching the surface seismic survey with the synthetic seismic survey may ensure that the surface seismic survey may be calibrated in actual depth.

Abstract: The present disclosure relates to a method to determine the phase of a signal when transmitter and receiver circuits use separate clocks. A discrepancy between the separate clocks is determined, as is a correction factor between the separate clocks. The phase is determined using a measured time of arrival of the signal, the determined discrepancy, and the determined correction factor. A drift factor and an expected start time of a pulse sequence may be used to determine the discrepancy. A start time of a pulse within the pulse sequence is determined and used to determine the correction factor. The method works by either absolute synchronization of the separate clocks, or by making the measurements independent of clock synchronization.

Abstract: A disclosed example method involves receiving a first signal transmitted into a reservoir from a production installation in a formation at a wellsite, and determining an apparent resistance of the reservoir based on the first signal. A distance between a fluid extraction tool and a fluid distribution is determined based on the apparent resistance.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: Inductive couplers for use in a downhole environment are described. An example inductive coupler for use in a downhole environment includes a body defining a cavity and magnetic material positioned in the cavity. The example inductive coupler also includes a coil adjacent the magnetic material, the coil formed with a number of turns of wire, and a first metal cover coupled to the body to enclose the cavity. The metal cover being electrically coupled to the body to form a substantially contiguous electrically conductive surface surrounding the cavity.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: Techniques involve determining the frequency-dependent dielectric permittivity spectrum of a rock sample. Determining the frequency-dependent dielectric permittivity may involve defining a series of electromagnetic measurement data having at least a measurement at a frequency from which a substantially frequency-independent value of dielectric permittivity ?? can be obtained. The electromagnetic measurement data also includes measurements at different frequencies from which values for frequency-dependent dielectric permittivity ?rock (f) can be obtained. Using these measurements, the frequency-dependent spectrum of the sample may be determined.

Abstract: A technique utilizes the acquisition of data from desired subterranean regions via a logging system. The logging system is constructed for use in a wellbore and comprises a transmitter module having a transmitter antenna. Additionally, the logging system utilizes a receiver module spaced from the transmitter module and having a receiver antenna. The transmitter antenna and the receiver antenna are oriented to enable sensitivity in desired directions, such as ahead of the logging system.

Abstract: A resistivity array having a modular design includes a transmitter module with at least one antenna, wherein the transmitter module has connectors on both ends adapted to connect with other downhole tools; and a receiver module with at least one antenna, wherein the transmitter module has connectors on both ends adapted to connect with other downhole tools; and wherein the transmitter module and the receiver module are spaced apart on a drill string and separated by at least one downhole tool. Each transmitter and receiver module may comprise at least one antenna coil with a magnetic moment orientation not limited to the tool longitudinal direction. A spacing between the transmitter and receiver module may be selected based on expected reservoir thickness.

Abstract: Systems and methods for estimating standoff and/or caliper in a wellbore for oil-based mud drilling are provided. The systems include a sensor having a primary electrode and at least two secondary electrodes, and an electronics subsystem having a controller and a processor for driving the system and correlating current measurements with standoff and/or caliper. The electrodes are positioned relative to one another such that there is a distinct flow of current between the primary electrode and each secondary electrode. In operation, a single excitation frequency is applied to the primary electrode and a simultaneous measurement of current flowing between the primary electrode and each secondary electrode is obtained. Standoff is estimated from the measurements. The estimations can be independent of formation properties when an appropriate excitation frequency is used.

Abstract: A method for determining the frequency-dependent dielectric permittivity spectrum of a rock sample, comprising:—defining a series of electromagnetic measurement data comprising at least a first measurement at a frequency from which a substantially frequency-independent value of dielectric permittivity ??, can be obtained; and at least second and third measurements at different frequencies from which values for frequency-dependent dielectric permittivity ?rock (f) can be obtained; and—using the first, second and third measurements to determine the frequency-dependent spectrum of the sample.

Abstract: The present disclosure relates to a method to determine a characteristic of a subsurface formation using electromagnetic coupling components. A downhole logging tool having one or more transmitters and one or more receivers, and being capable of measuring the electromagnetic coupling components is provided. The electromagnetic coupling components are measured using the downhole logging tool and used to form a 3-D Lateral Indicator and/or a 3-D Longitudinal Indicator. The 3-D Lateral Indicator and/or the 3-D Longitudinal Indicator are used to determine the characteristic of the subsurface formation.

Abstract: A technique utilizes the acquisition of data from desired subterranean regions via a logging system. The logging system is constructed for use in a wellbore and comprises a transmitter module having a transmitter antenna. Additionally, the logging system utilizes a receiver module spaced from the transmitter module and having a receiver antenna. The transmitter antenna and the receiver antenna are oriented to enable sensitivity in desired directions, such as ahead of the logging system.

Abstract: An apparatus for making a resistivity measurement of an underground formation surrounding a borehole is provided. The apparatus includes a conductive tool body, at least one current injector electrode positioned between the tool body and a wall of the bore hole, at least one current return electrode positioned between the tool body and the wall of the bore hole, an electrical measurement device configured to monitor a voltage or a current signal indicative of an impedance imbalance, a regulator connected to the electrical measurement device, whereby the regulator is configured to receive the voltage or the current signal indicative of the impedance imbalance and is configured to generate an adjustment signal based on the voltage or the current signal indicative of the impedance imbalance.

Abstract: A method to obtain gain-corrected measurements. A measurement tool having one or more arrays is provided, wherein the arrays include two co-located triaxial transmitters and two co-located triaxial receivers. Measurements are obtained using the transmitters and the receivers. Impedance matrices are formed from the obtained measurements and the impedance matrices are combined to provide gain-corrected measurements. The apparatus may alternatively be a while-drilling logging tool having one or more arrays, wherein each array comprises a transmitter, a receiver, and a buck, and wherein the signal received by the receiver is subtracted from the signal received by the buck or vice versa. A slotted shield may be incorporated into either embodiment of the tool. The slots may form one or more island elements. A material is disposed in the slots. The islands and shield body have complementary tapered sides that confine the islands within the shield body.

Abstract: Inductive couplers for use in a downhole environment are described. An example inductive coupler for use in a downhole environment includes a body defining a cavity and magnetic material positioned in the cavity. The example inductive coupler also includes a coil adjacent the magnetic material, the coil formed with a number of turns of wire, and a first metal cover coupled to the body to enclose the cavity. The metal cover being electrically coupled to the body to form a substantially contiguous electrically conductive surface surrounding the cavity.

Abstract: A system and method to determine earth formation properties by positioning a logging tool within a wellbore in the earth formation, the logging tool having a tool rotation axis and a first, a second, and a third tilted transmitter coil, and a tilted receiver coil; rotating the logging tool about the tool rotation axis; energizing each transmitter coil; measuring a coupling signal between each transmitter coil and the receiver coil for a plurality of angles of rotation; determining a coupling tensor; and determining the earth formation properties using the coupling tensor.

Abstract: The present disclosure relates to a method to determine the phase of a signal when transmitter and receiver circuits use separate clocks. A discrepancy between the separate clocks is determined, as is a correction factor between the separate clocks. The phase is determined using a measured time of arrival of the signal, the determined discrepancy, and the determined correction factor. A drift factor and an expected start time of a pulse sequence may be used to determine the discrepancy. A start time of a pulse within the pulse sequence is determined and used to determine the correction factor. The method works by either absolute synchronization of the separate clocks, or by making the measurements independent of clock synchronization.

Abstract: Method and system for visualizing one or more properties of a subterranean earth formation while drilling a borehole using probability information from a modeling process. Probability waveforms based on information from a plurality of borehole stations may be plotted, either alone or superimposed onto other graphical representations, to provide a visual display that is easily interpreted by a user to make geosteering decisions. The probability waveforms include peaked sections that are proportional to the amount of uncertainty or error associated with a boundary estimate at a particular distance from an axis of the borehole. By providing a visual display of the uncertainty, a user can make better geosteering decisions.