Methods and apparatus for evaluating an earth formation for generating a numerical model comprising an expression equating a representation for the effective conductivity under Archie's law with respect to direct current with a function for the effective conductivity representative of the mixing model with respect to direct current; and solving a system of equations to obtain values for the Archie parameters including at least i) the expression; ii) a second expression equating a first order variation of the representation with a first order variation of the function with respect to water saturation of the formation (Sw); and iii) a third expression equating a first order variation of the representation with a first order variation of the function with respect to porosity of the formation (φ). The second and third expressions may equate derivatives of the representation with derivatives of the function.

Methods and apparatus for evaluating an earth formation for generating a numerical model comprising an expression equating a representation for the effective conductivity under Archie's law with respect to direct current with a function for the effective conductivity representative of the mixing model with respect to direct current; and solving a system of equations to obtain values for the Archie parameters including at least i) the expression; ii) a second expression equating a first order variation of the representation with a first order variation of the function with respect to water saturation of the formation (Sw); and iii) a third expression equating a first order variation of the representation with a first order variation of the function with respect to porosity of the formation (φ). The second and third expressions may equate derivatives of the representation with derivatives of the function.

During a drilling operation, drilling mud is degaussed to remove magnetic interference that may disrupt measurements.

During a drilling operation, drilling mud is degaussed to remove magnetic interference that may disrupt measurements.

Methods may include emplacing a resistivity logging tool in a borehole; stimulating an interval of the formation in the borehole; obtaining at least one resistivity log of the interval of the formation, wherein the resistivity log comprises a survey of one or more depths into the formation; determining a radial invasion of the stimulating fluid into the interval of the formation; and inverting the radial invasion to obtain an input and entering the input into an effective medium model; solving the effective medium model and generating an effective wormhole radius profile and thickness for the interval of the formation.

Methods may include emplacing a resistivity logging tool in a borehole; stimulating an interval of the formation in the borehole; obtaining at least one resistivity log of the interval of the formation, wherein the resistivity log comprises a survey of one or more depths into the formation; determining a radial invasion of the stimulating fluid into the interval of the formation; and inverting the radial invasion to obtain an input and entering the input into an effective medium model; solving the effective medium model and generating an effective wormhole radius profile and thickness for the interval of the formation.

Systems and methods of the present disclosure relate to calibration of resistivity logging tool. A method to calibrate a resistivity logging tool comprises disposing the resistivity logging tool into a formation; acquiring a signal at each logging point with the resistivity logging tool; assuming a formation model for a first set of continuous logging points in the formation; inverting all of the signals for unknown model parameters of the formation model, wherein the formation model is the same for all of the continuous logging points in the first set; assigning at least one calibration coefficient to each type of signal, wherein the calibration coefficients are the same for the first set; and building an unknown vector that includes the unknown model parameters and the calibration coefficients, to calibrate the resistivity logging tool.

Systems and methods of the present disclosure relate to calibration of resistivity logging tool. A method to calibrate a resistivity logging tool comprises disposing the resistivity logging tool into a formation; acquiring a signal at each logging point with the resistivity logging tool; assuming a formation model for a first set of continuous logging points in the formation; inverting all of the signals for unknown model parameters of the formation model, wherein the formation model is the same for all of the continuous logging points in the first set; assigning at least one calibration coefficient to each type of signal, wherein the calibration coefficients are the same for the first set; and building an unknown vector that includes the unknown model parameters and the calibration coefficients, to calibrate the resistivity logging tool.

A system can include a first wireless coupler and a second wireless coupler. The first wireless coupler can include a first laminated core that can be wrapped around a tubular and a first wire wrapped around the first laminated core. The second wireless coupler can include a second wire that can be positioned coaxially around the first wire and at a distance from the first wire for facilitating wireless power transfer between the first wireless coupler and the second wireless coupler. The second wireless coupler may or may not include a second laminated core wrapped around the second wire.

A system includes a tool to dispose in a wellbore lined with pipe. The tool includes first and second receiver coils having a non-uniform winding along a longitudinal axis, a third receiver coil having a non-uniform winding coaxial with at least one of the first and second receiver coils, and a transmitter. The system includes a processor to execute instructions to perform operations including causing the transmitter to emit an induced magnetic field, measuring the induced magnetic field using the first receiver coil to create a first measurement and using the first and second receiver coils to create a second measurement. The operations include determining a static magnetic field, selecting the first or second measurement based on a magnitude of the static magnetic field to determine a selected measurement, and determining at least one property of the pipe using the selected measurement.