Abstract: An induction logging tool having concentric transmitter and receiver antennas can be used to make measurements of earth formations at frequencies up to 500 MHz. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. Litz winding is used in the coils to minimize eddy current losses. The antennas may be formed on a flexible circuit board.

Abstract: Multicomponent induction measurements may underestimate the anisotropy in formations where the bedding changes with distance from the borehole. The measurements may still be used to determine horizontal and vertical resistivity, and to identify complicated bedding structure such as that associated with channel sands and turbidite deposits. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.

Abstract: An induction logging tool having transmitter and receiver antennas is used to make measurements of earth formations. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. The induction measurements are inverted using a linearized model. The model parameters are determined in part from caliper measurements.

Abstract: Measurements made by a multi-component induction logging tool may be corrected for tool eccentricity or the presence of a fracture in the earth formation. The corrected measurements may then be used in conjunction with a multi-array measurement to determine horizontal and vertical formation resistivity.

Abstract: A resistivity imaging device injects currents in two orthogonal directions using two pairs of return electrodes and performing impedance measurements of the buttons placed between the returns.

Abstract: A pad mounted resistivity imaging device includes at least one transmitter and two or more arrays of receivers. Analysis of the received signals is done using either amplitude and phase differences between the arrays of receivers, or by analyzing amplitude and phase differences between the transmitters and the receivers. With operating frequencies in excess of 10 MHz, high resolution images of boreholes are obtained.

Abstract: Phase-sensitive measurements are made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation at a plurality of frequencies. From the phase sensitive measurements, the formation resistivity can be determined with higher sensitivity than is possible with the single frequency measurements. Tool standoff can also be determined from a knowledge of the mud resistivity and/or dielectric constant. Formation resistivity may also be determined when the effect of formation capacitance cannot be ignored.

Abstract: Impedance measurements made by a galvanic resistivity tool in a borehole in an earth formation are corrected by a factor that depends on the mud conductivity and the mud dielectric constant. Standoff measurements are not necessary.

Abstract: Measurements made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation are corrected using the tool standoff. The correction involves removing a calibration signal determined in a medium of high conductivity from the measured impedance. The magnitude and/or the real part of the impedance may be used.

Abstract: An induction logging tool having transmitter and receiver antennas is used to make measurements of earth formations. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. The induction measurements are inverted using a linearized model. The model parameters are determined in part from caliper measurements.

Abstract: An induction logging tool having concentric transmitter and receiver antennas can be used to make measurements of earth formations at frequencies up to 500 MHz. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. Litz winding is used in the coils to minimize eddy current losses. The antennas may be formed on a flexible circuit board.

Abstract: A pad mounted resistivity imaging device includes at least one transmitter and two or more arrays of receivers. Analysis of the received signals is done using either amplitude and phase differences between the arrays of receivers, or by analyzing amplitude and phase differences between the transmitters and the receivers. With operating frequencies in excess of 10 MHz, high resolution images of boreholes are obtained.

Abstract: An induction logging tool is used on a MWD bottom hole assembly. Due to the finite, nonzero, conductivity of the mandrel, conventional multi frequency focusing (MFF) does not work. A correction is made to the induction logging data to give measurements simulating a perfectly conducting mandrel. MFF can then be applied to the corrected data to give formation resistivities.