Abstract: A downhole logging system includes a plurality of spaced modules that provide a distributed transmitter/receiver arrangement. The system also includes an inter-module spacing control tool that operates to change a spacing between a transmitter and at least one receiver of the distributed transmitter/receiver arrangement. A related downhole logging method includes deploying a plurality of spaced modules in a borehole, wherein the spaced modules provide a distributed transmitter/receiver arrangement. The method also includes changing a spacing between a transmitter and at least one receiver of the distributed transmitter/receiver arrangement. The method also includes performing logging operations based on the changed spacing between the transmitter and the at least one receiver of the distributed transmitter/receiver arrangement.

Abstract: Disclosed embodiments include various borehole imaging tools and methods to provide sensing surface configurations for improving the assessment of anisotropy in layered formations. In at least some embodiments, the borehole imaging tools employ a unitary conductive body to provide a wall-contacting face with grooves that define multiple elongated sensing surfaces. This wall-contacting face can be provided on an extendable sensor pad of a wireline logging tool or embedded on the outer surface of a LWD stabilizer fin. Toroids may be seated in the grooves around each elongated sensing surface for measuring the current flow through each sensing surface. The elongated sensing surfaces can be configured in arranged in pairs as a series of rectangular-shaped grooves that are aligned perpendicularly to each other within each of the pairs to improve detection of anisotropy in thin layered formations and improves the sensitivity to dipping in anisotropic formations.

Abstract: The structural integrity and reliability of a downhole tool or mandrel may be improved by implementation of a design and configuration that does not require several separate components to be coupled together. A button recessed within an insulation layer may be installed within a groove or recess of the downhole tool. The isolation layer electrically isolates the button from the downhole tool. The button and the isolation layer are installed such that the top surface of either does not extend beyond the outer surface of the downhole tool. Recessing the button and isolation layer in this manner prevents undue wear on the downhole tool as well as the button and isolation layer. The buttons may be arranged so that when excited the buttons may detect the presence of a target objects located at various distances, directions, and orientations from the downhole tool.

Abstract: Planning and real time optimization of one or more modules of a downhole tool provide efficient and cost-effective deployment of a measurement system, for example, for a ranging tool. Considerations of the environment and type of operation may be considered prior to the deployment of a downhole tool such that the downhole tool comprises modules that may be optimized. Certain modules may be activated for specific operations without having to extract the downhole tool as all modules necessary to perform the specific tasks for a given operation are included prior to deployment of the downhole tool. The one or more modules may be optimized in real time based, for example, on received measurements or previous survey results. The modularity of the downhole tool allows for flexibility in fine tuning the tool according to a varying formation environment and other parameters.

Abstract: The structural integrity and reliability of a downhole tool or mandrel may be improved by implementation of a design and configuration that does not require several separate components to be coupled together. An insulating sleeve is wrapped around the outside of a mandrel. Electrodes, both transmit and return, are wrapped around the insulating sleeve. The outside diameter of the mandrel is increased but the structural integrity and reliability of the mandrel is maintained as no gap sub is used to electrically isolate the electrodes from the mandrel. The insulating sleeve may be tapered at the edges to prevent excessive wear on the sleeve. The insulating sleeve may also extend the full distance between the electrodes to provide even more insulation.

Abstract: A tool for influencing electrically conductive paths using ferrofluids in a downhole system. 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: Apparatus, systems, and methods may operate to detect anomalous formation resistivity values within measured formation resistivity data, based on mud resistivity associated with a borehole in a geological formation, the measured formation resistivity data comprising the anomalous formation resistivity values and acceptable formation resistivity values. Additional activity may include transforming the anomalous formation resistivity values into corrected formation resistivity values, inverting the corrected formation resistivity values and the acceptable formation resistivity values to provide true resistivity values for a geological formation, and operating a controlled device according to the true resistivity values for the geological formation. Additional apparatus, systems, and methods are disclosed.

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: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to estimate a value for a mud cake parameter to provide an estimated mud cake parameter value; to generate, in a solution operation, a formation parameter value and an adjusted mud cake parameter value using the estimated mud cake parameter value; and to provide corrected galvanic tool resistivity measurements based on at least the adjusted mud cake parameter value. Additional apparatus, systems, and methods are disclosed.

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 system and method for measuring a formation property in a wellbore is disclosed. In the method, an acoustic measurement tool is introduced into a wellbore. The acoustic measurement tool may include a transmitter and a plurality of sensors. At least one of the plurality of sensors may be positioned in a non-uniform spacing configuration. The transmitter may transmit energy into the formation. The plurality of sensors may measure energy received from the formation. Additionally, a time semblance of the formation may be determined using at least one time semblance algorithm generalized for non-uniform sensor spacing.

Abstract: Various embodiments include apparatus and methods to land a well in a target zone with minimal or no overshoot of a target zone. The well may be directed to a target in the target zone based on the separation distance between a transmitter sensor (212) and a receiver sensor (214) being sufficiently large to detect a boundary of the target zone from a distance from the boundary of the target zone such that collected received signals from activating the transmitter sensor (212) can be processed in a time that provides minimal or no overshoot of a target zone. Additional apparatus, systems, and methods are disclosed.

Abstract: According to aspects of the present disclosure, systems and methods for optimizing deep resistivity measurements are described herein. The method may include obtaining one or more first multi-component measurements from a downhole tool disposed in a borehole. The downhole tool may comprise multi-component antennae. A relative structural dip angle, ?, of the downhole tool relative to formations may be determined, for example, through the use of an additional downhole tool, or computationally using the one or more first multi-component measurements. A tilt angle of at least one of the multi-component antenna may be adjusted, with the adjusted tilt angle being based on the dip angle. The method may further include obtaining one or more second multi-component measurements associated with the adjusted tilt angle, and determining a formation characteristic based, at least in part, on the one or more second multi-component measurements, without including or considering formation anisotropy effects.

Abstract: Methods and systems are described that can be used for locating conductive bodies such as wellbore casing or piping disposed below the earth's surface. An electrical current can be excited in a conductive body in each wellbore in a given area to produce a magnetic field, and the magnetic field can be detected by a ranging tool. Location and current parameters can be determined for an estimated number of wellbores producing non-negligible contributions to the magnetic field, and the estimated number of wellbores can be adjusted until the number of contributing wellbores is determined. Location solutions can be returned for each of the contributing wellbores, and the location solutions can be employed to facilitate exploration of drilling applications such as well avoidance, well intersection and/or steam assisted gravity drainage (SAGD) steering operations.

Abstract: Disclosed herein are multicomponent borehole radar tools and methods. At least some tool embodiments employ at least two antennas that receive reflections of electromagnetic pulses transmitted from the tool. A processor processes the receive signals to identify reflection signals and to determine a direction and/or distance to the sources of the reflection signals. Possible sources include formation boundaries, fluid boundaries, cased wells, and other features that cause contrasts in electromagnetic properties. In addition to reflection signals, the measured responses may include direct signal measurements that are useful for determining formation resistivity and permittivity. Each of the antennas may transmit and receive, and they may be collocated to reduce tool size and reduce processing complexity. Disclosed logging tool examples employ both electric and magnetic dipole antennas.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to acquire multiple output values provided by at least one elongated, unitary acoustic sensor operating as a secondary propagation medium. The sensor has multiple mechanical-to-electrical conversion probe points along its length, to provide corresponding multiple output values proportional to mechanical movement along the length of the sensor, the mechanical movement being induced by acoustic waves in a primary propagation medium comprising a geological formation and borehole fluid. Further activity may include processing the output values to determine slowness in an acoustic wave propagating between at least two of the probe points. Additional apparatus, systems, and methods are disclosed.

Abstract: Apparatus, systems, and methods may operate to correct measured resistivity data for borehole effects to provide borehole-corrected apparent resistivity data for a non-invaded formation. Additional activity may include inverting the measured resistivity data or the borehole-corrected apparent resistivity data to provide non-invaded true resistivity values for the non-invaded formation, inverting the measured resistivity data to provide invaded true resistivity values for an invaded formation, determining true resistivity values for a geological formation associated with the measured resistivity data as a weighted combination of the non-invaded true resistivity values and the invaded true resistivity values, and operating a controlled device according to the true resistivity values for the geological formation.

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: An example method for downhole operations using a magnetic monopole includes positioning at least one of a transmitter and a receiver within a first borehole. At least one of the transmitter and the receiver may be a magnetic monopole. The transmitter may generate a first magnetic field, and the receiver may measure a signal corresponding to the first magnetic field. A control unit communicably coupled to the receiver may determine at least one characteristic using the received signal.

Abstract: A ranging system utilizes gradiometric data to determine the distance between a first and second well without any knowledge or involvement of the borehole or formation characteristics. In general, this is achieved by deploying a downhole assembly comprising transmitters and receivers having magnetic dipoles, along with bucking receivers positioned between the transmitters and receivers, wherein the gradient field is measured in a radial direction along the downhole assembly.