A method for signal communication between a well drilling instrument and the Earth's surface includes generating an electromagnetic field in an instrument disposed in drill string used to drill a wellbore. The electromagnetic field comprises encoded measurements from at least one sensor associated with the instrument. A signal is measured corresponding to an amplitude, phase or frequency of the electromagnetic field. The measurements are decoded from the measured signal. The measured signal comprises at least one of a voltage imparted across a capacitive electrode proximate ground surface and a galvanic electrode in contact with the ground surface, and a voltage imparted across two capacitive electrodes each proximate a ground surface and separated from each other by a known distance.

Disclosed are methods and systems that include a multiple-tube electrode assembly. An embodiment discloses an electrode assembly, comprising: a carrier body comprising an elongated support; and electrically conducting surfaces longitudinally spaced along the carrier body, wherein the electrically conducting surfaces are electrically coupled in parallel.

Disclosed are methods and apparatus for electromagnetic surveying using dynamically-selected source waveforms. In accordance with an embodiment of the invention, a source waveform is adapted by dynamically selecting a source waveform from the set of pre-calculated waveform sequences. The dynamic selection of the source waveform may depend on a measured background noise level. Other embodiments, aspects, and features are also disclosed.

A vertical bipole source in a borehole generates a vertical bipole flow. The vertical bipole flow generates mutually orthogonal time-domain B-field data. Magnetic receivers at a surface location receive the time-domain B-field data and determine elements of a hydrocarbon reservoir using a 3D EM inversion technique. The vertical bipole source may extend into the borehole or be a virtual bipole source located at a surface location above a reservoir.

To provide an exploration system that electromagnetically explores a target structure, including: a magnetic field generation apparatus that generates a magnetic field toward the target structure; and a magnetic field detection apparatus that detects a magnetic field that propagates from the target structure, the propagated magnetic field being generated due to the magnetic field generated by the magnetic field generation apparatus, wherein the magnetic field detection apparatus has a communication part that transmits information of the detected magnetic field to an external device in synchronization with a timing at which the magnetic field generation apparatus generates the magnetic field and a timing at which the generation of the magnetic field is stopped.

Disclosed are methods and systems for producing bipole source modeling with reduced computational loads. A method may comprise receiving first electromagnetic data and second electromagnetic data from a first shotpoint and a second of a marine electromagnetic survey, modelling a first electromagnetic field and second electromagnetic field for one or more dipole sources of a bipole source and combining a plurality of data points to provide an approximation of an electromagnetic field for the bipole source. A system may comprise electromagnetic sensors, a bipole source, wherein the bipole source comprise a pair of electrodes that are separated by a distance, wherein the bipole source is configured to generate an electromagnetic field, and a data processing system configured to receive electromagnetic data from a plurality of shotpoints of the bipole source and model electromagnetic fields for one or more dipole sources of the bipole source from the electromagnetic data.

Disclosed is a three-dimensional directional transient electromagnetic advanced detection device, wherein the CPU and the bus communication end of the transient electromagnetic transmitting module are both connected to the system bus, the signal output end of the transient electromagnetic transmitting module is connected to the transient electromagnetic transmitting coil outside the borehole to be detected, the signal input end of the electromagnetic signal receiving module is connected to the signal output ends of the three-dimensional magnetic field sensor and the one-dimensional Z-directional electric field sensor, the signal output end of the electromagnetic signal receiving module is connected to the electromagnetic signal input end of the SCM, the communication end of the first memory is connected to the data storage end of the SCM, the communication end of the three-dimensional electronic compass is connected to the compass signal communication end of the SCM, the host data communication of the SCM is connected to the second optical cable port of the local host through the first optical cable port and the optical cable. The device can detect harmful geological bodies such as aquifer and water-conducting channels and make a intensive and effective detection forecast.

A marine survey system can include a first cable including a first end configured to be coupled to a direct current (DC) power supply on a marine survey vessel and a support module coupled to a second end of the first cable and configured to receive power therefrom. A first electrode of towable electromagnetic (EM) source equipment can be coupled to the support module and configured to receive power therefrom. A depth control device can be coupled to the first electrode and configured to control a depth of the first electrode. A first end of a second cable can be coupled to the support module and configured to receive power therefrom. A second electrode of the towable EM source equipment can be coupled to a second end of the second cable and configured to receive power therefrom.

Disclosed is a three-dimensional digital virtual imaging device for stratigraphic texture of borehole core, wherein the probe depth counting pulley is mounted on the lifting wire frame, the output shaft of the motor is configured to drive the reel to rotate, and one end of the cable is connected to the cable transfer node of the retractable reel, the signal input end of the borehole imaging trajectory measuring probe of the on-site imaging host is electrically connected to one end of the cable through the cable transfer node of the retractable reel, the cable is wound on the retractable reel, a retractable line is controlled by the retractable reel, the cable is extended and retracted on the probe depth counting pulley, the probe depth counting pulley records the length of the retractable line of the cable, the depth feedback signal output end of the depth counting pulley is connected to the depth feedback signal input end of the on-site imaging host, the motor control signal output end of the on-site imaging host is connected to the control signal input end of the motor, and the signal output end of the borehole imaging trajectory measuring probe is connected to the other end of the cable. It can automatically generate borehole video, two-dimensional digital virtual borehole core image and 3D borehole trajectory in real time.

The invention relates to a method and device for measuring the burial depth of lines that are being laid increasingly under a soil surface on land and in water. In order to increase a measurement precision, more than one excitation or transmission coil is used, which extends in an xy plane, the transmission coils are positioned next to one another in a span extending essentially perpendicular to a center axis of the line and are moved over the line along this center axis; the transmission coils transmit electromagnetic pulses in a time-lagged fashion as a primary signal, and receiver coils are used, which are distributed across the array of transmission coils in the xy plane and measure in at least two axes extending orthogonally to one another; and all of the receiver coils measure secondary signals in reaction to the transmission of a primary pulse by the transmission coils.