Abstract: Material properties between a wellbore and a casing having a partition separating respective domains inside and outside the casing are evaluated by disposing at least one ultrasonic transmitter and a plurality of ultrasonic receivers in longitudinally spaced-apart relationship alongside the partition inside the casing. The ultrasonic transmitter is activated to form ultrasonic waveforms comprising propagated quasi leaky-Lamb waves constituting flexural waves having symmetric and antisymmetric zero-order modes within the partition. A time-shift is applied to the received flexural waves so that the respective time-shifted waveforms corresponding to each of the flexural waves arrive at the same time.

Abstract: Material properties between a wellbore and a casing having a partition separating respective domains inside and outside the casing are evaluated by disposing at least one ultrasonic transmitter and a plurality of ultrasonic receivers in longitudinally spaced-apart relationship alongside the partition inside the casing. The ultrasonic transmitter is activated to form ultrasonic waveforms comprising propagated quasi leaky-Lamb waves constituting flexural waves having symmetric and antisymmetric zero-order modes within the partition. A time-shift is applied to the received flexural waves so that the respective time-shifted waveforms corresponding to each of the flexural waves arrive at the same time.

Abstract: Electromagnetic (EM) inversion includes determining an electric field associated with EM data within a predetermined sensitivity area around each of a plurality of source positions, iteratively inverting the electric field for a subsurface resistivity EM model indicative of a subterranean formation for each of a plurality of EM electrical resistivity data cells within each of the predetermined sensitivity areas, and storing results of the iterative inversion. A linear system of equations comprising a Jacobian matrix is generated based on the iterative inversion, the linear system of equations is stored, and the linear system of equations is solved at each iteration of the iterative inversion to update the subsurface resistivity EM model until a convergence criterion is met. A resistivity map based on the updated subsurface resistivity EM model can be produced.

Abstract: Electromagnetic (EM) inversion includes determining an electric field associated with EM data within a predetermined sensitivity area around each of a plurality of source positions, iteratively inverting the electric field for a subsurface resistivity EM model indicative of a subterranean formation for each of a plurality of EM electrical resistivity data cells within each of the predetermined sensitivity areas, and storing results of the iterative inversion. A linear system of equations comprising a Jacobian matrix is generated based on the iterative inversion, the linear system of equations is stored, and the linear system of equations is solved at each iteration of the iterative inversion to update the subsurface resistivity EM model until a convergence criterion is met. A resistivity map based on the updated subsurface resistivity EM model can be produced.