Abstract: An ultrasonic transducer device is disclosed. The device includes a body and an ultrasonic transducer mounted onto the body. The ultrasonic transducer comprises a shoulder and an O-ring placed on the shoulder. The O-ring substantially covers the interface between the ultrasonic transducer and the body.

Abstract: A downhole galvanic logging system including a first transmitter electrode configured to convey an exciter current into a formation and a second transmitter electrode configured to receive a return current from the formation. A first transmission line being coupled to the first transmitter electrode and configured to carry the exciter current, and a second transmission line being coupled to the second transmitter electrode and configured to carry the return current. The transmission lines can be arranged in a twisted pattern. A receiver device is positioned between the transmitter electrodes along an axial length of the downhole galvanic logging system. The receiver device can be configured to detect an electrical signal that is proportional to a resistivity of the formation. The second transmitter electrode can be coupled to one end of the receiver device with the second transmission line coupled to the second transmitter electrode through the receiver device.

Abstract: An example variable reluctance device includes a load structure connected to an armature through a connecting arm. The armature is positioned between two oppositely oriented core structures. A structural frame secures the core structures in a fixed position, forming gap regions between the core structures and the armature, forming a magnetic circuit. The armature is resiliently centered between the core structures by a spring, such that the gaps and are approximately equal in width when the armature is at rest. The device further includes a magnetic substance within the gaps that is compressed or stretched to allow movement of the armature.

Abstract: Apparatus and methods are described, such as for obtaining information indicative of a formation resistivity using an electromagnetic formation evaluation tool apparatus. For example, the electromagnetic formation evaluation tool apparatus includes exciter electrodes configured to transmit and receive a formation current. A first exciter electrode may be insulated from a conductive apparatus housing and a second exciter electrode may be coupled to the conductive apparatus housing. Monitor electrodes may be insulated from the conductive apparatus housing. A receiver circuit may be coupled to the monitor electrodes and configured to measure a voltage differential between the monitor electrodes. A power amplifier circuit may be coupled to the first exciter electrode and the conductive apparatus housing and configured to generate the formation current wherein the conductive apparatus housing provides a return path to the power amplifier circuit for the formation current.

Abstract: A piezoelectric transducer is mounted in a housing. An impedance matching layer is provided between the piezoelectric transducer and the housing. The impedance matching layer includes high-permittivity regions that have a first permittivity, and low-permittivity regions that separate the high-permittivity regions and have a second permittivity. The second permittivity is lower than the first permittivity.

Abstract: The magnet and antenna assemblies of a logging tool can be arranged according to geometries optimal for concentric or eccentric well logging operations. In an example configuration, a logging tool can include a magnet, a magnetic core made of a magnetically permeable material, and an antenna. The outward path of the antenna can be positioned along a surface of the magnetically permeable magnetic core that faces away from the magnet, and the return path of the antenna can also be positioned along a surface that faces away from the magnet.

Abstract: A tool for providing modifiable structures in a wellbore using ferrofluids in a downhole system is provided. The downhole system can include a tool body, a source of ferrofluid, and a magnet. The magnet can magnetically couple with the ferrofluid from the source for arranging the ferrofluid adjacent for modifying a parameter of an object coupled with or in the tool body when the tool body is positioned in the wellbore.

Abstract: Downhole electronics assemblies including a modular carrier including a top rail and a bottom rail, the top and bottom rails each including a pair of longitudinally extending sides and the top rail providing one or more ribs that extend between the longitudinally extending sides of the top rail. A circuit board is positionable between the top and bottom rails and has a top side and a bottom side and one or more electronic components mounted on at least one of the top and bottom sides. One or more damping pads interpose the circuit board and a host downhole tool such that contact between the circuit board and the host downhole tool is prevented.

Abstract: Apparatus and methods are described, such as for obtaining information indicative of a formation resistivity using an electromagnetic formation evaluation tool apparatus. For example, the electromagnetic formation evaluation tool apparatus includes exciter electrodes configured to transmit and receive a formation current. A first exciter electrode may be insulated from a conductive apparatus housing and a second exciter electrode may be coupled to the conductive apparatus housing. Monitor electrodes may be insulated from the conductive apparatus housing. A receiver circuit may be coupled to the monitor electrodes and configured to measure a voltage differential between the monitor electrodes. A power amplifier circuit may be coupled to the first exciter electrode and the conductive apparatus housing and configured to generate the formation current wherein the conductive apparatus housing provides a return path to the power amplifier circuit for the formation current.

Abstract: The magnet and antenna assemblies of a logging tool can be arranged according to geometries optimal for concentric or eccentric well logging operations. In an example configuration, a logging tool can include a magnet, a magnetic core made of a magnetically permeable material, and an antenna. The outward path of the antenna can be positioned along a surface of the magnetically permeable magnetic core that faces away from the magnet, and the return path of the antenna can also be positioned along a surface that faces away from the magnet.

Abstract: A focused acoustic transducer suitable for use in a downhole environment is disclosed. At least some embodiments employ a disk of piezoelectric material with low planar coupling and low Poisson's ratio mounted on a backing material and sealed inside an enclosure. The piezoelectric material disk has a pattern of electrodes deposited on an otherwise smooth, ungrooved surface. Despite the lack of grooves, the material's low planar coupling and low Poisson's ratio enables the electrodes to operate in a phased relationship to provide and receive focused acoustic pulses. Moreover, the elimination of deep cuts offers a much lower cost of construction. The electrode material may be any conductive material, though silver and silver alloys are contemplated. The patterning of electrodes can occur during the deposition process (e.g., using a silk-screen or other printing technique) or afterwards (e.g., mechanically or chemically with an etch technique that uses a pre- or post-deposition photoresist layer).

Abstract: Apparatus and techniques are described, such as for obtaining information indicative of a formation resistivity, such as using information from a galvanic measurement apparatus. A resistive parameter related to a geologic formation is estimated through use of a model. An electrical excitation is coupled from a well tool in a borehole to the geologic formation. Induced voltages resulting from the excitation are received using monitor electrodes selected according to the specified excitation mode, including receiving magnitude and phase information corresponding to the induced voltages. The resistive parameter of the model is then determined using the magnitude and phase information of the received voltages, and using magnitude and phase information about the excitation.

Abstract: A tool for providing modifiable structures in a wellbore using ferrofluids in a downhole system is provided. The downhole system can include a tool body, a source of ferrofluid, and a magnet. The magnet can magnetically couple with the ferrofluid from the source for arranging the ferrofluid adjacent for modifying a parameter of an object coupled with or in the tool body when the tool body is positioned in the wellbore.

Abstract: Technologies are described for reducing distortion in amplified signals in well logging tools based on spectral analyses of the amplified signals. For example, a system includes a well logging tool. The well logging tool includes an excitation source to direct an excitation signal towards an environment adjacent a wellbore and a receiver to amplify a probe signal received from the environment adjacent the wellbore in response to the excitation signal. The system also includes a feedback module to receive the amplified signal. The feedback module includes a spectrum analyzer module to spectrally analyze the amplified signal to generate spectral information of the amplified signal; and a controller module to determine, from the spectral information, whether the amplified signal includes distortion, and if so, to issue a feedback signal to the excitation source or the receiver to cause at least a reduction of the distortion in the amplified signal.

Abstract: A tool for isolating objects in a wellbore using ferrofluids in a downhole system is provided. The downhole system can include a tool body, a source of ferrofluid, and a magnet. The magnet can magnetically couple with the ferrofluid from the source for arranging the ferrofluid adjacent to the tool body for isolating an object positioned in a wellbore from effects of fluids present in the wellbore.

Abstract: A tool for enhancing or directing magnetic fields using ferrofluids in a downhole system is provided. The downhole system can include a tool body, a source of ferrofluid, and a positioning magnet. The positioning magnet can magnetically couple with the ferrofluid from the source for enhancing or directing a magnetic field through at least a portion of an annulus between the tool body and a wellbore formation.

Abstract: A tool for influencing electrically conductive paths using ferrofluids in a downhole system is provided. The downhole system can include a tool body, a source of ferrofluid, and a magnet. The magnet can provide a magnetic field that influences an electrically conductive path within an annulus between the tool body and a wellbore formation by arranging the ferrofluid from the source in the annulus.

Abstract: A piezoelectric transducer is mounted in a housing. An impedance matching layer is provided between the piezoelectric transducer and the housing. The impedance matching layer includes high-permittivity regions that have a first permittivity, and low-permittivity regions that separate the high-permittivity regions and have a second permittivity. The second permittivity is lower than the first permittivity.

Abstract: A system and method for monitoring a wellbore are disclosed herein. A pulse generator comprises a plurality of ports, wherein a first one of the plurality of ports is coupled to a first location of interest and a second one of the plurality of ports is coupled to a second location of interest. An electromagnetic pulse is generated at the first port and the second port. A reflected electromagnetic pulse is received at the first port and the second port. In another embodiment, the pulses are received at a separate pulse receiver with a plurality of receiving ports. A data storage device is coupled to the pulse generator or the pulse receiver, and data relating to the reflected magnetic pulse is stored at the data storage device.

Abstract: A device includes a piezoelectric transducer. The transducer has N independent transducer regions. N is an integer. Each of the N independent transducer regions has a thickness. Each of the N independent transducer regions has an acoustic impedance AIT. Each of the N independent transducer regions is independently excitable to oscillate in the thickness mode when electrically excited by a potential difference applied across the thickness. The device further includes a first impedance matching layer having an acoustic impedance AI1 and AIT and a borehole fluid acoustic impedance AIBF. The first impedance matching layer is situated such that an acoustic signal emitted by the piezoelectric transducer will pass through the second impedance matching layer. The device further includes a second impedance matching layer having an acoustic impedance AI2 between AI1 and AIBF.