Inversion of enhanced-sensitivity controlled source electromagnetic data can include combining measured controlled source electromagnetic (CSEM) data onto a common set of virtual receiver positions for each of a plurality of positions of a source along a survey path, determining a steering vector that enhances a sensitivity of the measured CSEM data to a subsurface resistivity variation, and performing an inversion using the measured CSEM data and modeled CSEM data, each having the steering vector applied thereto as a data weight, to better identify the subsurface resistivity variation.

Disclosed is a method for extracting IP information in a TEM response of a grounded-wire source, comprising the following steps: 1) obtaining subsurface resistivity through inversion of a vertical magnetic field less influenced by an IP effect; 2) obtaining an electric field response not influenced by the IP effect based on forward modeling of the obtained underground electrical structure; 3) removing the influence of the IP effect on an observed response to obtain a pure IP response; and 4) inverting the obtained IP response to obtain IP information of polarizability, a frequency dependence, and a time constant. The method of the present invention provides a new idea for further extracting IP information in a TEM response.

A method allowing the determination of the location and/or the orientation of a magnetic field source in space, and more particularly a method for determining the relative position in space of at least one magnetic field source in relation to at least one magnetic field sensor comprises the steps of acquiring measurements of the magnetic field, computing a solution of the expression of the magnetic field generated by at least one magnetic field source by modeling each magnetic field source by an element chosen from among a superposition of solenoids and a superposition of charged planes, then by estimating the value of a complete elliptic integral linked to the model by an algorithm using a Landen transformation and computing at least one element chosen from among the position and the orientation of each magnetic field source.

Various methods for performing inversion of data obtained from a CSEM survey in order to determine resistivity values in a surveyed space are disclosed. A method includes initializing an objective functional dependent measured and modeled electric field data and iteratively minimizing the objective functional to produce an estimated set of expansion coefficients for generating a multi-dimensional record of resistivity values. The set of expansion coefficients is dependent on a resistivity model, which in turn is used to generate an electric field model in the form of a multi-dimensional grid having a number of grid points. Thus, instead of performing the inversion for each point in the grid, the record of resistivity values is generated based on the set of coefficients. The number of coefficients may be at least one decimal order of magnitude less than the number of grid points, and thus the computational effort is reduced.

A method of solving a geophysical inverse problem for estimating a physical parameter, the method comprising providing a model vector representing the physical parameter, transforming the model vector by a first operator to provide a first transformed model vector, solve the inverse problem for the first transformed model vector to provide a first solution, transforming the model vector by a second operator to produce a second transformed model vector, solve the inverse problem for the second transformed model vector to provide a second solution, calculating a weighted sum of the first solution and the second solution.

Marine survey data resulting from a first signal comprising a signal representing a flat spectral far-field pressure generated by a marine vibrator source swept over a frequency range according to a time function of motion such that acceleration of the marine vibrator source is a flat function in a frequency domain can be used to improve full waveform inversion. For example, full waveform inversion can be performed using the marine survey data received from the first signal and from a second signal generated by an impulsive seismic source to estimate a physical property of a subsurface location.

A method for estimating at least one geophysical property is disclosed. The method includes using a plurality of transmitter electrodes distributed in a conductive medium, periodically passing rectangular current impulses through the media; collecting a sequence of sounding data between each of the impulses with a receiver electrode disposed between the plurality, determining a first difference and a second difference of the electric potential between points of the collected data; when each of the transmitters is excited, acquiring a focused measurement by simultaneously calculating a combination of at least one orthogonally weighted measurement and at least one axially weighted measurement obtained by the receiver, wherein the weighting is obtained from a condition of equipotentiality in four outer electrodes of the receiver; and, applying a time-differentiation technique to obtain deep measurements that exhibit low noise contribution from shallow features. An apparatus is also disclosed.

Provided is a metal detector capable of quickly and accurately ascertaining a noise generating situation. A metal detector generates a magnetic field in an inspection region and detects a change in the magnetic field in the inspection region to detect a foreign substance in an inspection object passing through the inspection region. The metal detector measures the change in the magnetic field of the inspection region while changing an inspection frequency, performs frequency analysis of the measurement result, and displays an obtained frequency distribution diagram on the display unit as a noise diagnosis result. In the frequency distribution diagram, target foreign substance reference lines are displayed.

This invention relates to devices and processes for geophysical prospecting, subsurface fluid monitoring and, more particular, to the use of interferometric techniques using Control Source Electromagnetic (CSEM) and Magnetoturelic (MT) signals to create images of sub-surface structures and fluids.

Method for estimating geological properties in a subsurface region using multiple types of geophysical data (21). An initial physical properties model 22 is constructed. Some parameters in the model are frozen (23) and optionally portions of the model wave number and spatial domains (24) and the data frequency and data time domains (25), are also frozen. Then, a joint inversion (26) of the multiple data types is performed to calculate an update to the model only for the portions that are not frozen. The converged model (27) for this inversion is used as a new starting model, and the process is repeated (28), possibly several times, unfreezing more parameters and data each time until the desired spatial and parameter resolution (29) has been achieved.