Abstract: A downhole tool includes a chassis having a bore formed axially-therethrough. An antenna is positioned radially-outward from the chassis. A collar is positioned radially-outward from the antenna. A window is defined radially-through the collar. An insert is positioned in the window. The insert is made at least partially of a ceramic material.

Abstract: Identifying the dielectric constant and/or the electrical resistivity of part of a geological formation may reveal useful characteristics of the geological formation. This disclosure provides methods, systems, and machine-readable media to determine dielectric constant or electrical resistivity, or both, using contraction mapping. Specifically, contraction mapping may be used with a function of wavenumber k to iteratively solve for values of dielectric constant and electrical resistivity until convergence is achieved. This may allow for convergence to a solution without computing partial derivatives and/or with fewer iterations than previous techniques.

Abstract: A downhole tool includes a chassis having a bore formed axially-therethrough. An antenna is positioned radially-outward from the chassis. A collar is positioned radially-outward from the antenna. A window is defined radially-through the collar. An insert is positioned in the window. The insert is made at least partially of a ceramic material.

Abstract: A tool is for use in a borehole during drilling with a drilling fluid circulating in the borehole. The tool may include a housing, a plurality of spaced apart radio frequency (RF) transmitters carried by the housing, spaced apart RF receivers carried by the housing, and a controller to communicate with the plurality of transmitters and the receivers. The controller may, at a given depth within the borehole, determine attenuation resistivity measurements and phase-shift resistivity measurements both corresponding to different radial distances from the borehole. The controller may also determine when a fracture has occurred in the geological formation at the given depth allowing the drilling fluid to intrude into the geological formation based upon the attenuation resistivity measurements and the phase-shift resistivity measurements.

Abstract: Identifying the dielectric constant and/or the electrical resistivity of part of a geological formation may reveal useful characteristics of the geological formation. This disclosure provides methods, systems, and machine-readable media to determine dielectric constant or electrical resistivity, or both, using contraction mapping. Specifically, contraction mapping may be used with a function of wavenumber k to iteratively solve for values of dielectric constant and electrical resistivity until convergence is achieved. This may allow for convergence to a solution without computing partial derivatives and/or with fewer iterations than previous techniques.

Abstract: An inductive coupler apparatus have a first inductive coupler with a first magnetic center shaft having a recessed portion, a first outer magnetic layer disposed around the first magnetic center shaft, and a first coil disposed around the first magnetic center shaft and disposed within the first outer magnetic layer and a second inductive coupler with a second magnetic center shaft having a recessed portion, a second outer magnetic layer disposed around the second magnetic center shaft, and a second coil disposed around the second magnetic center shaft and disposed within the second outer magnetic layer. When the first and second inductive couplers are in the coupled position the inductive couplers can provide for the transmission of power and/or communication between downhole tools in a bottom hole assembly.

Abstract: Example inductive couplers are provided herein. The inductive couplers can provide for the transmission of power and/or communication between downhole tools in a bottom hole assembly.