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.

A system and method for controlled-source electromagnetic exploration is based on staggered frequency excitation of crossed sources. Different high-order pseudo-random signals are transmitted using two sources, respectively, each set of high-order pseudo-random signals may contain sufficient frequencies within a same complete frequency range, exploration frequencies of the two sets of signals are completely staggered, simultaneous transmission by the two field sources is implemented, and different polarization modes do not affect each other and are separated from each other. Moreover, different measuring line directions at a receiving terminal can be observed simultaneously, and each measuring point has two polarization directions, thus greatly improving the exploration efficiency and the data volume.

A system and method for controlled-source electromagnetic exploration is based on staggered frequency excitation of crossed sources. Different high-order pseudo-random signals are transmitted using two sources, respectively, each set of high-order pseudo-random signals may contain sufficient frequencies within a same complete frequency range, exploration frequencies of the two sets of signals are completely staggered, simultaneous transmission by the two field sources is implemented, and different polarization modes do not affect each other and are separated from each other. Moreover, different measuring line directions at a receiving terminal can be observed simultaneously, and each measuring point has two polarization directions, thus greatly improving the exploration efficiency and the data volume.

Various downhole logging tools and methods of using and making the same are disclosed. In one aspect, a downhole logging tool for inspecting one or more well tubulars includes a housing adapted to be supported in the one or more well tubulars by a support cable. A first transmitter, a second transmitter and a third transmitter are positioned in longitudinally spaced-apart relation in the housing and are operable to generate magnetic fields. Driving circuitry is operatively coupled to the first transmitter, the second transmitter and the third transmitter to selectively fire the first transmitter, the second transmitter and the third transmitter in multiple transmission modes to generate magnetic fields to stimulate pulsed eddy currents in the one or more well tubulars. A first receiver is positioned in the housing to sense decaying magnetic fields created by the pulsed eddy currents. Electronic circuitry is operatively coupled to the first receiver to determine a parameter of interest of the one or more well tubular from the sensed decaying magnetic fields.

An apparatus for airborne electromagnetic surveying is provided, comprising a central hub defining an equatorial plane, a transmitter loop, and radials connecting the hub to the transmitter loop. The loop generally lies in a plane during flight, and comprises loop sections, some of which are connected with flexible joints allowing the loop to flex out of the plane during lift-offs and landings. A loop section comprises current conducting elements connected to current conducting elements of adjacent loop sections forming a transmitter loop circuit. A radial connects to the hub at a point that is substantially offset from the transmitter loop plane, thereby contributing to the stability of the transmitter loop connection point in an up-down direction relative to the hub. Additionally, a loop section comprising rigid conductive elements retained in a spaced-apart relationship by a frame member is also provided.

A high-frequency data and/or power transmission system suitable for downhole use including signal/power couplers, transmission line segments and signal repeaters. Signals and power are/is transmitted between couplers and/or between couplers and repeaters by means of electromagnetic resonance coupling. In at least a portion of the system, the transmission line segments form parallel data paths and the repeaters provide crossover capability between the data/power paths, thereby significantly improving reliability. The invention also includes methods of transmitting data and/or distributing high-frequency power through a downhole transmission system including multiple data/power paths and multiple crossovers wherein a fault location in one data/power path is bypassed by routing data and/or power to a parallel data/power path by means of electromagnetic resonance coupling.

Disclosed is a separated multi-core transmitting device based on a ground transient electromagnetic method, comprising: a rectangular transmitting coil enclosed by a cable I, a cable II, a cable III, and a cable IV. Each of the cable I, the cable II, the cable III, and the cable IV is provided with N wires. Two ends of each of the N wires is provided with a sub connector and a female connector, respectively. The sub connectors and the female connectors are detachably connected through sub connector interfaces and female connector interfaces. A first wire of the female connectors of the cable I is led out to serve as a positive electrode of a transient electromagnetic instrument transmitter, and a last wire of the sub connectors of the cable IV is led out to serve as a negative electrode of the transient electromagnetic instrument transmitter.

Disclosed are methods and systems for conditioning electrodes while deployed in the sea with a marine electromagnetic survey system. An embodiment of the method may comprise deploying electrodes in seawater during a marine electromagnetic survey. The method further may comprise coupling at least one of the electrodes to a controllable current/voltage source while the electrodes are deployed in the seawater. The method further may comprise sending a first conditioning signal from the controllable current/voltage source to the at least one of the electrodes coupled to the controllable current/voltage source.

Nulling utility locators including a transmitter element, a sensing element, and an electronic circuit for processing signals from the transmitting element to at least partially cancel each other and determine information associated with a buried utility are disclosed.

A device and method for measuring spectrum parameters of a formation outcrop and a rock mass are provided. An excitation signal is generated by a direct digital synthesis (DDS) module of a signal transmission portion. A constant voltage mode or a constant current mode is adopted for observation. After the signal passes through a constant voltage/constant current module, a constant high-voltage signal source or a current source signal with constant current output is formed and output to ground through grounding electrodes A and B to establish a stable observation signal field source. Geoelectric response information under the excitation of each frequency signal is acquired by a signal receiving portion through grounding electrodes M and N, processed and send out to a microcontroller unit (MCU) for display and storage. The spectrum parameters at different depths are observed by adjusting geometric dimensions of AB and MN.