Abstract: Optical detection apparatus (300) comprising an optical detector (302, 304, 306), a detector amplifier (336, 338, 340), and switching means, e.g., a multiplexer (344, 348), for dynamically selecting at least one of the optical detector or the detector amplifier by switching from among at least two alternative optical detectors and/or at least two detector amplifiers such as to minimize noise equivalent power (NEP) of a selected detector or combination of detector and amplifier under given operating conditions.

Abstract: An electrically stimulated electrode system comprises injection and return electrodes and a power supply for causing electrical current to flow through a subterranean formation. An electronic system for the injection electrode includes: a power harvester extracting electrical power from current flowing in the injection electrode, a control for the injection electrode current, a sensor of the injection electrode and/or formation, or a telemetry for the injection electrode and/or formation, or any combination thereof. A sensor comprises: a pair of spaced apart electrodes, a power conversion device connected to the spaced apart electrodes for providing electrical power, and a processor providing a representation of a current.

Abstract: A method for correcting a motion related distortion in a sensor measurement comprises establishing a reference position in a borehole. A parameter of interest is measured at a plurality of toolface angles as the tool makes a revolution in the borehole. A distance to a wall of the borehole is measured associated with each parameter of interest measurement. A lateral motion of the tool is measured between each parameter of interest measurement, and a toolface angle of the tool is measured at each parameter of interest measurement. A controller comprising a processor acts according to programmed instructions to calculate a correction to the parameter of interest measurement referenced to the reference position based at least partly on the measured tool motion.

Abstract: A system for communicating information in a borehole between tool assemblies in a tool string includes receiving an information signal and separating a first signal that may be a power and low speed signal. A second signal is separated and demodulated from the information signal. The first signal and second signal are transmit to electronic devices that process data from an earth formation. After the first and second signals are transmit to one or more electronic devices, the signals are modulated and/or filtered and then combined into the information signal. The first signal is at one frequency and the second signal is at a different frequency. The apparatus includes a main signal line that couples to a second signal line and third signal line in the tool assembly.

Abstract: A system and method for determining material resistivity. A current of one or more frequencies is generated using a circuitry (225). The one or more frequencies is directed using one or more electrodes (215) into a surrounding material. The resistivity of the material surrounding the electrodes (215) and a drilling tool (210) is measured by detecting the current at the one or more frequencies.

Abstract: A method for correcting a motion related distortion in a sensor measurement comprises establishing a reference position in a borehole. A parameter of interest is measured at a plurality of toolface angles as the tool makes a revolution in the borehole. A distance to a wall of the borehole is measured associated with each parameter of interest measurement. A lateral motion of the tool is measured between each parameter of interest measurement, and a toolface angle of the tool is measured at each parameter of interest measurement. A controller comprising a processor acts according to programmed instructions to calculate a correction to the parameter of interest measurement referenced to the reference position based at least partly on the measured tool motion.

Abstract: A system for communicating information in a borehole between tool assemblies in a tool string includes receiving an information signal and separating a first signal that may be a power and low speed signal. A second signal is separated and demodulated from the information signal. The first signal and second signal are transmit to electronic devices that process data from an earth formation. After the first and second signals are transmit to one or more electronic devices, the signals are modulated and/or filtered and then combined into the information signal. The first signal is at one frequency and the second signal is at a different frequency. The apparatus includes a main signal line that couples to a second signal line and third signal line in the tool assembly.

Abstract: A system for communicating information in a borehole between tool assemblies in a tool string includes receiving an information signal and separating a first signal that may be a power and low speed signal. A second signal is separated and demodulated from the information signal. The first signal and second signal are transmit to electronic devices that process data from an earth formation. After the first and second signals are transmit to one or more electronic devices, the signals are modulated and/or filtered and then combined into the information signal. The first signal is at one frequency and the second signal is at a different frequency. The apparatus includes a main signal line that couples to a second signal line and third signal line in the tool assembly.

Abstract: An apparatus and method for minimizing the effects of a common mode voltage signal in downhole logging tools utilized to determine the resistivity of an adjacent portion of a borehole wall. Two current electrodes are energized by an excitation source to create an oscillatory electric field in a borehole wall. A voltage drop across a segment of the borehole wall is measured by two voltage electrodes, and the differential voltage is used in combination with a measured current flow to determine a resistivity value for the borehole wall. A common mode voltage in front of the two voltage electrodes is measured and minimized by controlling the excitation source, thereby reducing the resistivity measurement error.

Abstract: Oil-based mud imaging systems and methods having standoff compensation. In some embodiments, disclosed logging systems include a logging tool in communication with surface computing facilities. The logging tool is provided with a sensor array having at least two voltage electrodes positioned between two current electrodes energized by an excitation source to create an oscillatory electric field in a borehole wall. The two current electrodes are each shielded with conductive shields to prevent current leakage into the logging tool body. A common mode voltage is measured, and the phase and amplitude of the excitation source is controlled to reduce the difference between the common mode voltage and reference voltage of a voltage detector. The logging tool is further provided with electronics coupled to the voltage detector and the current electrodes to determine a differential voltage between the voltage electrodes and two current flows from separate ones of the current electrodes.

Abstract: A system for communicating information in a borehole between tool assemblies in a tool string includes receiving an information signal and separating a first signal that may be a power and low speed signal. A second signal is separated and demodulated from the information signal. The first signal and second signal are transmit to electronic devices that process data from an earth formation. After the first and second signals are transmit to one or more electronic devices, the signals are modulated and/or filtered and then combined into the information signal. The first signal is at one frequency and the second signal is at a different frequency. The apparatus includes a main signal line that couples to a second signal line and third signal line in the tool assembly.

Abstract: Method and apparatus are provided to accelerate the cooling of thermally sensitive components in a chamber of a downhole instrument assembly. In accordance with the invention, a passage is formed in the chamber and a fluid is conveyed through the passage to cool the components to the desired temperature. By using the method and apparatus of the present invention the amount of time to cool the components is dramatically less than the time required for cooling using conventional techniques.

Abstract: A system and method for calculating the lateral velocity of a rotating drilling tool within a borehole, the system comprising: a pair of accelerometers placed oppositely across the drilling tool axis of rotation and two magnetometers. The method comprises: reading tool radial acceleration signals ar1, ar2, and tangential acceleration signals, at1 and at3, obtained with a quadrature accelerometer detection system; reading Bx and By, the tool's magnetic phase data, from two orthogonally placed magnetometers; determining the rotational phase angle of the drilling tool relative to the earth's gravity field by first determining the tool's magnetic phase, and the phase shift between the tool's magnetic phase and gravity phase; and processing the foregoing data to yield a lateral tool velocity which optionally compensates for the effect of gravity on the accelerometers, or converts the lateral tool velocity from the tool reference frame to the borehole reference frame, or does both.

Abstract: A system and method for calculating the lateral velocity of a rotating drilling tool within a borehole, the system comprising: a pair of accelerometers placed oppositely across the drilling tool axis of rotation and two magnetometers. The method comprises: reading tool radial acceleration signals ar1, ar2, and tangential acceleration signals, at1 and at3, obtained with a quadrature accelerometer detection system; reading Bx and By, the tool's magnetic phase data, from two orthogonally placed magnetometers; determining the rotational phase angle of the drilling tool relative to the earth's gravity field by first determining the tool's magnetic phase, and the phase shift between the tool's magnetic phase and gravity phase; and processing the foregoing data to yield a lateral tool velocity which optionally compensates for the effect of gravity on the accelerometers, or converts the lateral tool velocity from the tool reference frame to the borehole reference frame, or does both.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An apparatus and method for reducing crosstalk and other noise sources in downhole tools is disclosed. Due to confined space in the downhole tool environment and the fact that the transmit path utilizes significantly more electrical power than the receive path, electromagnetic noise easily couples between adjacent circuitry. The specification discloses a phase-reversal element that can selectively allow the received signal to pass unaffected, or which can cause a phase reversal of the received signal. A digital signal processor samples the received signal, which after receipt but before sampling has noise induced thereon. Thereafter, the digital signal processor samples the phase reversed received signal, which likewise has the noise induced thereon after receipt but before sampling. Subtracting the first sampled signal from the second produces a resultant signal in which the noise is substantially reduced.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An apparatus and method for reducing crosstalk and other noise sources in downhole tools is disclosed. Due to confined space in the downhole tool environment and the fact that the transmit path utilizes significantly more electrical power than the receive path, electromagnetic noise easily couples between adjacent circuitry. The specification discloses a phase-reversal element that can selectively allow the received signal to pass unaffected, or which can cause a phase reversal of the received signal. A digital signal processor samples the received signal, which after receipt but before sampling has noise induced thereon. Thereafter, the digital signal processor samples the phase reversed received signal, which likewise has the noise induced thereon after receipt but before sampling. Subtracting the first sampled signal from the second produces a resultant signal in which the noise is substantially reduced.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: A system and method for calculating the lateral velocity of a rotating drilling tool within a borehole, the system comprising: a pair of accelerometers placed oppositely across the drilling tool axis of rotation and two magnetometers.