Abstract: A method for inverting dielectric logging tool measurement data to estimate an electrical characteristic of an earth formation includes: receiving measurement data from the logging tool having a transmitter antenna and receiver antennas spaced known distances from the transmitter antenna; establishing an equation relating magnetic field measurements made by the receiver antennas to the distances and a wave vector; establishing an error equation that quantifies a difference between the magnetic field measurements made by the receiver antennas to magnetic field measurements made by the receiver antennas that would be obtained with an estimated formation electrical characteristic; calculating an error using the error equation for an initial estimated value of the wave vector that comprises a term having a first number multiplied times a second number of radians to provide a plurality of calculated errors; and determining a minimum error from the plurality of calculated errors to estimate the electrical character

Abstract: A method for inverting dielectric logging tool measurement data to estimate an electrical characteristic of an earth formation includes: receiving measurement data from the logging tool having a transmitter antenna and receiver antennas spaced known distances from the transmitter antenna; establishing an equation relating magnetic field measurements made by the receiver antennas to the distances and a wave vector; establishing an error equation that quantifies a difference between the magnetic field measurements made by the receiver antennas to magnetic field measurements made by the receiver antennas that would be obtained with an estimated formation electrical characteristic; calculating an error using the error equation for an initial estimated value of the wave vector that comprises a term having a first number multiplied times a second number of radians to provide a plurality of calculated errors; and determining a minimum error from the plurality of calculated errors to estimate the electrical character

Abstract: A method for increasing sensitivity in a measurement of at least one of magnitude and direction of resistivity in a subsurface material, the method including: performing a first set of measurements of resistivity of the subsurface material using a first logging instrument; constructing a model of a background signal using the first set of measurements; calculating a predicted response of a second logging instrument to the model of the background signal; performing a second set of measurements of at least one of magnitude and direction of resistivity of the subsurface material using the second logging instrument; deriving a second logging instrument response from the second set of measurements; and subtracting the predicted response from the second logging instrument response to produce a corrected response that has greater sensitivity than the second logging instrument response.

Abstract: A phase error in measurements made by a resistivity logging tool is estimated by positioning the tool above a conducting surface. Deviation of the measured phase difference between the transmitter and the receiver from 90° gives the phase error in the electronics. 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.

Abstract: A method for increasing sensitivity in a measurement of at least one of magnitude and direction of resistivity in a subsurface material, the method including: performing a first set of measurements of resistivity of the subsurface material using a first logging instrument; constructing a model of a background signal using the first set of measurements; calculating a predicted response of a second logging instrument to the model of the background signal; performing a second set of measurements of at least one of magnitude and direction of resistivity of the subsurface material using the second logging instrument; deriving a second logging instrument response from the second set of measurements; and subtracting the predicted response from the second logging instrument response to produce a corrected response that has greater sensitivity than the second logging instrument response.

Abstract: Resistivity measurements are made at a plurality of frequencies. An asymptotic high-frequency limit is determined and the electrical efficiency is estimated as a ratio of the high frequency resistivity limit to the low frequency resistivity. From the electrical efficiency, petrophysical parameters of a rock such as porosity and water saturation can be estimated.

Abstract: Resistivity measurements are made at a plurality of frequencies. An asymptotic high-frequency limit is determined and the electrical efficiency is estimated as a ratio of the high frequency resistivity limit to the low frequency resistivity. From the electrical efficiency, petrophysical parameters of a rock such as porosity and water saturation can be estimated.

Abstract: A phase error in measurements made by a resistivity logging tool is estimated by positioning the tool above a conducting surface. Deviation of the measured phase difference between the transmitter and the receiver from 90° gives the phase error in the electronics. 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.

Abstract: Cross-component measurements made at a plurality of toolface angles are processed to remove bias. The amplitude of the resulting sinusoid is used to estimate a distance to an interface in an earth formation.

Abstract: Resistivity measurements are made at a plurality of frequencies. An asymptotic high-frequency limit is determined and the electrical efficiency is estimated as a ratio of the high frequency resistivity limit to the low frequency resistivity. From the electrical efficiency, petrophysical parameters of a rock such as porosity and water saturation can be estimated.

Abstract: Resistivity measurements are made at a plurality of frequencies. An asymptotic high-frequency limit is determined and the electrical efficiency is estimated as a ratio of the high frequency resistivity limit to the low frequency resistivity. From the electrical efficiency, petrophysical parameters of a rock such as porosity and water saturation can be estimated. 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.

Abstract: The present invention provides a measurement-while-drilling (MWD) system having a downhole computer and multiple downhole sensors. Relatively large amounts of basic or “raw” data are measured by downhole sensors, and these data are processed within a downhole computer to be reduced to parameters of interest, which may be utilized to control the drilling operation by downhole devices, stored downhole, telemetered to the surface, or both. The measurements may be correlated downhole with stored reference data thereby providing additional information pertaining to the drilling operation. Downhole depth correlation between downhole measured parameters may be made by utilizing surface determined or downhole determined borehole depth.

Abstract: An arrangement of two closely spaced transmitters and two spaced apart receivers symmetrically disposed about the transmitters in a measurement while drilling tool avoids the effects of mutual coupling between the receivers. In one method of operation of the transmitters, each transmitter is sequentially activated while the other transmitter is decoupled to eliminate mutual coupling, and the recorded signals processed to take advantage of reciprocity relations. In another method of operation, both transmitters are operated simultaneously with one relative polarity and then with another relative polarity, to eliminate the effects of mutual coupling and to take advantage of reciprocity relations.

Abstract: The present invention provides a measurement-while-drilling (MWD) system having a downhole computer and multiple downhole sensors. Relatively large amounts of basic or "raw" data are measured by downhole sensors, and these data are processed within a downhole computer to be reduced to parameters of interest, which may be utilized to control the drilling operation by downhole devices, stored downhole, telemetered to the surface, or both. The measurements may be correlated downhole with stored reference data thereby providing additional information pertaining to the drilling operation. Downhole depth correlation between downhole measured parameters may be made by utilizing surface determined or downhole determined borehole depth.

Abstract: The current invention is directed toward the use of a downhole computer and downhole storage within a measurement-while-drilling (MWD) downhole subassembly to process data from the response of a plurality of sensors of different classes or one or more sensors of the same class which exhibit different measure points and vertical resolutions. Classes or types of sensors applicable to the invention include, but are not limited to, electromagnetic, acoustic, and nuclear. Sensor measurements are made essentially simultaneously. In combining downhole responses from one or more sensors to obtain parameters of interest, a critical prerequisite is downhole depth correlation and vertical resolution matching of all sensor responses prior to combination.

Abstract: A wave propagation measurement-while-drilling system is used to determine selected formation and borehole properties. One or more transmitter-receiver pairs are utilized with the transmitter components operating at one or more frequencies to provide a measured data set. A model relating the borehole instrument response to a wide range of formation and borehole conditions is also utilized. Inversion techniques are employed to determine selected formation and borehole parameters of interest and to simultaneously correct the selected formation parametric measurements for the adverse effects of the borehole and formation bed boundaries thereby avoiding serial type corrections which can yield erroneous results in certain frequency ranges.

Abstract: There is disclosed herein an improved method for processing the output signals from the receiver coil of an induction logging tool to account for nonlinear attenuation and phase shift of the induced electromagnetic field in the subsurface formation as a function of formation conductivity. The method includes the calculation of a modified vertical geometrical factor at a plurality of sample intervals for each measure point. The vertical geometrical factor is modified at each sample interval according to an attenuation factor that is a function of the distance in skin depths between the sample interval and the measure point. Using the modified vertical geometrical factor at each sample interval, an approximation for the measured signal in the receiver coil at the measure point is calculated and compared to the skin-effect corrected conductivity at that point to obtain an improved approximation of true formation conductivity at the measure point.