A method and system for generating a logarithmic non-uniform pseudo-random electromagnetic exploration signal including: constructing two or more basic unit signals, according to an exploration requirement, that are stairstep signals obtained by superposing in-phase periodic square wave signals, a frequency ratio between adjacent periodic square wave signals is 2, and the two or more basic unit signals meet the following requirement: if a lowest dominant frequency in a first basic unit signal is a fundamental frequency, lowest frequencies of the remaining basic unit signal are l×2.sup.m times the fundamental frequency, where l is an odd number except 1, and m is a natural number; and superposing the two or more basic unit signals to obtain a logarithmic non-uniform 2.sup.n sequence pseudo-random signal. A logarithmic non-uniform 2.sup.n sequence stairstep signal is constructed within a limited frequency interval, and requirements of prospectors for a higher frequency density within a specific frequency interval are met.

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.

Concurrently measuring, correlating, and processing magnetic and electric field data includes measuring base band signals, and then up-converting those band signals to a higher frequency for filtering, while at the same time preserving phase and amplitude information. All timed elements in the system are rigorously synchronized. The increased data set results in improved signal-to-noise ratio and information correlation.

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 method of solving closed form exact solution for the field generated by a finite-length harmonic linear current source in a whole space. The vector magnetic potential formula of the finite-length harmonic linear current source containing a source point position vector is listed, the uniform current is subjected to cosine processing, and the current in the vector magnetic potential formula of the harmonic linear current source is expressed by a cosine function. The vector magnetic potential formula can be subjected to quadrature by an elementary function to obtain the closed form exact solution for the field generated by the finite-length harmonic linear current source in whole space. The cosine expression of the linear current source can better reflect the fundamental attributes of the electric dipole and harmonic current of linear current source in the conductive whole space. The obtained closed form exact solution is applicable in the all zone.

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.

An electrical prospecting signal transmission device capable of suppressing electromagnetic coupling interference, including a rectangular wave signal source, an output circuit for supplying power to the ground and a plurality of transmission channels. Each of the plurality of transmission channels includes an isolated driving circuit, a low-pass filter circuit and a power amplification circuit connected sequentially in series. The rectangular wave signal source is configured to generate a rectangular wave or a composite rectangular wave. A signal output terminal of the rectangular wave signal source is connected to an input terminal of the isolated driving circuit, and an output terminal of the power amplification circuit is connected to the output circuit to supply power to the ground.

Naturally-occurring, electromagnetic signals generated by interaction of solar wind with earth's magnetosphere adjacent a borehole are measured by an electromagnetic sensor positioned adjacent the borehole in the hydrocarbon-bearing formation. Electromagnetic signals generated within the borehole are measured over a period of time by a borehole sensor positioned within the borehole. The electromagnetic signals change over the period of time due to variations in fluid distributions within the hydrocarbon-bearing formation. Electromagnetic changes to the electromagnetic signals generated within the borehole and to the passive, naturally-occurring electromagnetic signals over the period of time are determined by one or more processors. A computational model of the hydrocarbon-bearing formation is generated based in part on the electromagnetic changes.

A method can include selecting a type of geophysical data; selecting a type of algorithm; generating synthetic geophysical data based at least in part on the algorithm; training a deep learning framework based at least in part on the synthetic geophysical data to generate a trained deep learning framework; receiving acquired geophysical data for a geologic environment; implementing the trained deep learning framework to generate interpretation results for the acquired geophysical data; and outputting the interpretation results.