Abstract: Systems and methods for geochemical sampling grid locations on a seafloor. At least one of the methods includes generating, using received seismic data, an image representing an interpretation of a seafloor horizon surface; extracting, from the image and based on the seismic data, one or more discontinuity attributes of the seafloor horizon surface; extracting, from the image and based on the seismic data, one or more amplitude attributes of a window extending below the seafloor horizon surface; combining the one or more discontinuity attributes and the one or more amplitude attributes; and selecting, using the image and based at least partly on the combining, one or more locations of the seafloor horizon surface for sampling.

Abstract: An electromagnetic data acquisition system and an associated method for measuring subsurface structures with electromagnetic fields is employed for removing near surface effects from borehole to surface electromagnetic data. Preferably, the system is used to obtain information about deep, target structures located deep below the Earth, especially in oil and gas fields, while mitigating the effect of near surface geological shallow structures on collected electromagnetic (EM) data by using a series of electromagnetic measurements and data treatments that preferentially illuminate near surface geologic shallow structures so that the shallow structures may be recovered separately from deep structures of interest.

Abstract: A method for efficiently calculating a subsurface distribution of electrical resistivity or conductivity generated by an electromagnetic (EM) source is provided wherein a significant fraction of the electric current produced by a source flows along a casing of a borehole. The method is comprised of two steps: calculating EM fields produced by the casing in the background lithology; and calculating EM fields caused by a resistivity anomaly in the presence of an EM field produced by the casing within a subsurface or survey model that does not include the casing.

Abstract: Methods and systems are provided to determine a property of an earth formation, comprising a mobile transmitter disposed at a predetermined elevated height above a surface of the earth formation, and one or more receivers moveably disposed in a wellbore penetrating the earth formation. Electromagnetic energy is transmitted from the mobile transmitter into the formation from a plurality of locations; and at the one or more receivers a signal is measured. Using the signal received by the one or more receivers, a property of the formation, such as resistivity, can be determined and mapped.

Abstract: A resistivity imaging device uses a line source in conjunction with an array of measure electrodes to reduce sensitivity to tool standoff when use in a borehole with oil-based mud.

Abstract: An apparatus for measuring radiated power of a terminal includes: an enclosure including a pair of couplers configured to couple an electromagnetic field radiated from the terminal or a substitution antenna and a measurement jig configured to rotate the terminal or the substitution antenna, the terminal or the substitution antenna being supposed to be arranged between the pair of couplers, with reference to at least one of X, Y, and Z axes; a driver installed outside the enclosure to drive the measurement jig; a signal generator configured to generate a feed signal transferred to the substitution antenna when the substitution antenna is arranged on the measurement jig; a feed signal transmitter configured to transfer the feed signal generated by the signal generator to the substitution antenna; and a spectrum analyzer configured to measure power of a radiated signal radiated from the terminal or the substitution antenna.

Abstract: Method for removing air wave noise from shallow water controlled source electromagnetic survey data, using only the measured data and conductivity values for sea water (140) and air. The method is a calculation performed numerically on CSEM data and resulting in an estimate of those data that would have been acquired had the water layer extended infinitely upward from the seafloor. No properties of the sub-sea sediments are used. Synthetic electromagnetic field data are generated for (a) an all water model (141) and (b) an air-water model (146-147) of the survey region. These simulated results are then used to calculate (148-150) electromagnetic field values corresponding to a water-sediment model with water replacing the air half space, which represent measured data adjusted to remove air wave noise.

Abstract: Method for survey design including configuring electrodes to reduce near-surface noise in the seismic response from an electroseismic survey of a subterranean formation. Different embodiments of the invention include (1) selective measurement of the surface noise to remove it from the data; (2) suppressing surface noise generation by reducing electric fields in the vicinity of some of the electrodes; (3) creating source signature differences between the near-surface seismic response and the deep response enabling the near surface response to be removed in data processing; (4) applying an external near-surface magnetic field to modulate the near-surface seismic response, enabling it to be removed in processing; and (5) constructing a partial Faraday cage to shield a near-surface region from fields generated by the electrodes.

Abstract: A mixed mode tool uses an inductive source and detects galvanic currents and/or potentials at electrodes in proximity to a borehole wall to produce a resistivity image of the earth formation. Alternative, the magnetic field produced by a galvanic current is detected by an antenna coil and used to produce a resistivity image. 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 understand that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method for controlled source electromagnetic Earth surveying includes deploying a plurality of electromagnetic sensors in a selected pattern at the top of an area of the Earth's subsurface to be surveyed. At least one of a transient electric field and a transient magnetic field is applied to the Earth in the vicinity of the sensors at a plurality of different positions. At least one of electric field amplitude and magnetic field amplitude at each of the sensors is recorded each time the transient electric field and/or magnetic field is applied. Each recording is adjusted for acquisition geometry. An image is generated corresponding to at least one sensor position using at least two stacked, adjusted recordings.

Abstract: A method and apparatus for minimizing direct coupling between transmitters and receivers on a downhole logging tool are disclosed. One embodiment includes a transmitter, a bucking device, and a plurality of receivers, where signals may be directly coupled from the transmitter into the receivers and signals may be indirectly coupled from the transmitter into the receivers through the formation and borehole environment. The bucking device minimizes the magnitude of the signals that are directly coupled from the transmitter into multiple receivers within the plurality. By varying the current in the bucking device, the bucking device minimizes the magnitude of the directly coupled signal of each receiver in the plurality, and each receiver may utilize a common bucking device.

Abstract: A method for seismic exploration using nonlinear conversions between electromagnetic and seismic energy, with particular attention to the electromagnetic source waveform used. According to the invention, seismic returns from a source waveform are correlated with a reference waveform, with both waveforms custom designed to minimize both correlation side lobes and interference from linear electroseismic effects. A waveform element is selected which may be sequenced by a binary or similar digital code embodying the desired custom design to generate an input sweep with the needed depth penetration and noise suppression. Correlation of the seismic response with the reference waveform in a data processing step mathematically aggregates the seismic response from the input sweep into a single wavelet. Preferred binary digital codes include prescribed variations of maximal length shift-register sequences. Also, an apparatus for generating the desired waveforms.

Abstract: A method for surface estimation of reservoir properties, wherein location of and average earth resistivities above, below, and horizontally adjacent to the subsurface geologic formation are first determined using geological and geophysical data in the vicinity of the subsurface geologic formation. Then dimensions and probing frequency for an electromagnetic source are determined to substantially maximize transmitted vertical and horizontal electric currents at the subsurface geologic formation, using the location and the average earth resistivities. Next, the electromagnetic source is activated at or near surface, approximately centered above the subsurface geologic formation and a plurality of components of electromagnetic response is measured with a receiver array. Geometrical and electrical parameter constraints are determined, using the geological and geophysical data.

Abstract: The invention is directed to an apparatus and method for locating objects in a body through the mapping and imaging of the conductivity profiles of such objects by applying a force to the object and/or body and measuring certain characteristics of the body responsive to the application of force. In accordance with a preferred embodiment, the force applied to the object and body is in the form of an electrical voltage or current such that electrical potentials, currents, and magnetic fields are generated throughout the subsurface site. The voltage, current, or magnetic field is then measured at the surface or the boundary of the body. An estimate of subsurface conductivity is then made and a conductivity profile generated by minimizing a loss function. Preferably, the loss function is in the form of the sum square of the differences between measurement values and a set of computed values based on a gradient approximation technique.

Abstract: An electromagnetic method is disclosed that can be used to map, track, and monitor subsurface water or solutions and related geologic structure including: groundwater, groundwater channels, groundwater structures, subsurface pollution plumes, locate the source of springs or seeps, map interconnected fracture or porous zones, map leaks in earthen dams, map leaks in drain fields, monitor changes in subsurface water flow, monitor changes in ion concentration in groundwater, monitor in situ leaching solution, monitor movement of heap leaching solutions, monitor changes in subsurface redox or reaction fronts, monitor underground chemical reactions, monitor subterranean bioreactions, or other subsurface waters and related geologic structures. An electric current is injected directly into the water or solution that is to be mapped, tracked, or monitored. It is also necessary to provide a return path for the injected electrical current.

Abstract: A method and apparatus used in providing resistivity measurement data of a sedimentary subsurface for developing and mapping an enhanced anomalous resistivity pattern. The enhanced subsurface resistivity pattern is associated with and an aid for finding oil and/or gas traps at various depths down to a basement of the sedimentary subsurface. The apparatus is disposed on a ground surface and includes an electric generator connected to a transmitter with a length of wire with grounded electrodes. When large amplitude, long period, square waves of current are sent from a transmission site through the transmitter and wire, secondary eddy currents are induced in the subsurface. The eddy currents induce magnetic field changes in the subsurface which can be measured at the surface of the earth with a magnetometer or induction coil. The magnetic field changes are received and recorded as time varying voltages at each sounding site.

Abstract: A method and a device for implementing the method, for geophysical surveying of an area (1) including continuous measurement of the earth's magnetic and electromagnetic field using a detector (6) held at a constant height (E) above the ground surface, in the order of one meter, while traversing in a criss-cross manner over the area (1) at speeds below a maximum speed (S), in the order of 10 km/h, and utilizing measured signal frequencies below a cutoff (F), being approximately the maximum speed (S) divided by twice the detector height (E), to indicate spatial variations in the measured field. Traversal distance can be measured on board the host vehicle and a real time output supplied. Simultaneously, using the same detector (6) and artificially induced magnetic fields generated by an inductive (2b and/or galvanic source (2a)), temporally varying fields having frequencies above the cutoff (F) can be measured and simply filtered out of the detector's (6) output for separate processing and storage.

Abstract: A sensor for sensing the location of objects buried in the loose sediment in the bed of the sea. A hollow, cylindrically symmetric, conductive shell is used to inject current into seawater at its tips along its axis. A sensor coil oriented along the axis ignores all magnetic fields except those along the axis, and is used to measure return signals. This is particularly useful in detecting dielectric objects buried in the sediment and in rejecting motion relative to the seabed.

Abstract: A logging-while-drilling system is disclosed in which a first subassembly is included near the drill bit, and this subassembly comprises a conducting body with measuring means disposed in it and a first toroidal coil antenna disposed on the body, means for coupling a local communication signal generated from the measuring means to the first toroidal coil antenna, and where the measuring means includes means to energize the first toroidal coil antenna with a measurement signal and means mounted on the conductive body to receive the measurement signal after it passes through the formations to be measured.

Abstract: This invention relates to the measurement of the longitudinal components of low frequency A.C. magnetic fields from within cased boreholes which are used to measure the geophysical properties of geological formations. The applied A.C. magnetic fields are generated by passing low frequency A.C. current through insulated wires or by conducting low frequency A.C. current through geological formations. The currents generating the applied A.C. magnetic fields are in the frequency range between 0.001 Hz and 20 Hz. The measured longitudinal components of the resulting total A.C. magnetic fields are responsive to various geophysical parameters which include the resistivities of the portions of the geological formations subject to said applied A.C. magnetic fields.

Abstract: A method for surface estimation of reservoir properties, wherein location of and average earth resistivities above, below, and horizontally adjacent to the subsurface geologic formation are first determined using geological and geophysical data in the vicinity of the subsurface geologic formation. Then dimensions and probing frequency for an electromagnetic source are determined to substantially maximize transmitted vertical and horizontal electric currents at the subsurface geologic formation, using the location and the average earth resistivities. Next, the electromagnetic source is activated at or near surface, approximately centered above the subsurface geologic formation and a plurality of components of electromagnetic response is measured with a receiver array. Geometrical and electrical parameter constraints are determined, using the geological and geophysical data.

Abstract: A method for surface estimation of reservoir properties, wherein location of and average earth resistivities above, below, and horizontally adjacent to the subsurface geologic formation are first determined using geological and geophysical data in the vicinity of the subsurface geologic formation. Then dimensions and probing frequency for an electromagnetic source are determined to substantially maximize transmitted vertical and horizontal electric currents at the subsurface geologic formation, using the location and the average earth resistivities. Next, the electromagnetic source is activated at or near surface, approximately centered above the subsurface geologic formation and a plurality of components of electromagnetic response is measured with a receiver array. Geometrical and electrical parameter constraints are determined, using the geological and geophysical data.

Abstract: A method for seismic exploration using nonlinear conversions between electromagnetic and seismic energy, with particular attention to the electromagnetic source waveform used. According to the invention, seismic returns from a source waveform are correlated with a reference waveform, with both waveforms custom designed to minimize both correlation side lobes and interference from linear electroseismic effects. A waveform element is selected which may be sequenced by a binary or similar digital code embodying the desired custom design to generate an input sweep with the needed depth penetration and noise suppression. Correlation of the seismic response with the reference waveform in a data processing step mathematically aggregates the seismic response from the input sweep into a single wavelet. Preferred binary digital codes include prescribed variations of maximal length shift-register sequences. Also, an apparatus for generating the desired waveforms.