Abstract: This disclosure describes a method, apparatus, and non-transitory computer-readable medium product for correcting a shale volume estimated from gamma ray information using a continuous radial profile of horizontal resistivity in the invaded zone and a continuous profile of anisotropy. The continuous radial profile of horizontal resistivity may be estimated by modeling a hydrodynamic evolution of the invaded zone (a) a step-wise radial profile of horizontal resistivity in the invaded zone as an initial estimate of horizontal resistivity in the invaded zone; (b) an estimated shallow resistivity at a borehole wall; and (c) an estimated horizontal conductance of the formation at an outer boundary of the borehole wall estimated from multi-component induction logging information.

Abstract: A method for imaging an earth formation includes estimating an apparent resistivity (AR) value and an apparent distance to a bedding plane (AD2B) value for each of a plurality of samples derived from measurements of a time-dependent transient electromagnetic signal, estimating an inversion-based resistivity value (IB-R) and an inversion-based distance to a bedding plane (IB-D2B) value at a first sample of each consecutive depth interval, wherein each depth interval includes a plurality of consecutive samples, and determining a difference between apparent values and the corresponding inversion-based values. The method further includes generating an image of the earth formation using the AR and AD2B values for the entire interval if the difference is less than a threshold value and generating an image of the earth formation using IB-R and IB-D2B values for the entire interval if the difference is greater than the threshold value.

Abstract: A method of processing electromagnetic signal data includes: disposing a downhole tool in a borehole in an earth formation, the downhole tool including at least one electromagnetic transmitter; performing a downhole electromagnetic operation, the operation including transmitting an electromagnetic pulse from the transmitter into the formation and measuring a time domain transient electromagnetic (TEM) signal over a selected time interval following a transmitter turn-off time; transforming the measured time domain TEM signal into a frequency domain TEM signal measured; and applying an inversion technique to the transformed frequency domain TEM signal to estimate one or more formation parameters.

Abstract: This disclosure describes a method, apparatus, and non-transitory computer-readable medium product for correcting a shale volume estimated from gamma ray information using a continuous radial profile of horizontal resistivity in the invaded zone and a continuous profile of anisotropy. The continuous radial profile of horizontal resistivity may be estimated by modeling a hydrodynamic evolution of the invaded zone (a) a step-wise radial profile of horizontal resistivity in the invaded zone as an initial estimate of horizontal resistivity in the invaded zone; (b) an estimated shallow resistivity at a borehole wall; and (c) an estimated horizontal conductance of the formation at an outer boundary of the borehole wall estimated from multi-component induction logging information.

Abstract: A system and method to compress transient signals are described. The system includes a transmitter disposed in a borehole to change a transmitted current and induce a current in an earth formation, and a receiver disposed in the borehole to receive the transient signals resulting from the transmitted current. The system also includes a processor to compress the transient signals, the processor compressing the transient signals based on a spline approximation method or an Eigen value method for each transient signal based on whether the spline approximation method or the Eigen value method results in a fewer number of parameters representing the transient signal.

Abstract: A system and method of estimating properties of a subsurface formation are described. The method includes transmitting an excitation current pulse into the formation, receiving an induced pulse used to generate input data, and performing an inversion on the input data using a lookup table based on a shape of the excitation current pulse to estimate the properties of the subsurface formation.

Abstract: A method for imaging an earth formation includes estimating an apparent resistivity (AR) value and an apparent distance to a bedding plane (AD2B) value for each of a plurality of samples derived from measurements of a time-dependent transient electromagnetic signal, estimating an inversion-based resistivity value (IB-R) and an inversion-based distance to a bedding plane (IB-D2B) value at a first sample of each consecutive depth interval, wherein each depth interval includes a plurality of consecutive samples, and determining a difference between apparent values and the corresponding inversion-based values. The method further includes generating an image of the earth formation using the AR and AD2B values for the entire interval if the difference is less than a threshold value and generating an image of the earth formation using IB-R and IB-D2B values for the entire interval if the difference is greater than the threshold value.

Abstract: A system and method to compress transient signals are described. The system includes a transmitter disposed in a borehole to change a transmitted current and induce a current in an earth formation, and a receiver disposed in the borehole to receive the transient signals resulting from the transmitted current. The system also includes a processor to compress the transient signals, the processor compressing the transient signals based on a spline approximation method or an Eigen value method for each transient signal based on whether the spline approximation method or the Eigen value method results in a fewer number of parameters representing the transient signal.

Abstract: A system and method to determine a dip angle and an azimuth angle of a formation are described. The system includes a transmitter disposed in a borehole to change a transmitted current to induce a current in an earth formation, and a receiver disposed in the borehole, spaced apart from the transmitter, to receive transient electromagnetic signals. The system also includes a processor to extract multi-time focusing (MTF) responses from the transient electromagnetic signals, determine a relative dip angle and a rotation of a tool comprising the transmitter and receiver based on the MTF responses, and estimate the dip angle and the azimuth angle of the formation based on the relative dip angle and the rotation of the tool.

Abstract: A system and method of estimating properties of a subsurface formation are described. The method includes transmitting an excitation current pulse into the formation, receiving an induced pulse used to generate input data, and performing an inversion on the input data using a lookup table based on a shape of the excitation current pulse to estimate the properties of the subsurface formation.

Abstract: A method of processing electromagnetic signal data includes: disposing a downhole tool in a borehole in an earth formation, the downhole tool including at least one electromagnetic transmitter; performing a downhole electromagnetic operation, the operation including transmitting an electromagnetic pulse from the transmitter into the formation and measuring a time domain transient electromagnetic (TEM) signal over a selected time interval following a transmitter turn-off time; transforming the measured time domain TEM signal into a frequency domain TEM signal measured; and applying an inversion technique to the transformed frequency domain TEM signal to estimate one or more formation parameters.

Abstract: Measurements made with an induction logging tool are responsive to formation conductivity and permittivity. The effect of permittivity can be substantially removed by multifrequency focusing.

Abstract: Measurements made with an induction logging tool are processed to provide a resistivity model of fluid invasion of the formation. Up to five zones can be determined over a radial distance of about 0.6 m. 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: Measurements made with an induction logging tool are processed to provide a resistivity model of fluid invasion of the formation. Up to five zones can be determined over a radial distance of about 0.6 m. 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: Measurements made with an induction logging tool are responsive to formation conductivity and permittivity. The effect of permittivity can be substantially removed by multifrequency focusing.