There is described apparatus for orienting at least one electromagnetic field sensor, a related receiver unit and method of use. The apparatus has an orientation detector having an output which is dependent upon an orientation of the electromagnetic field sensor, an actuator and a controller which is arranged in communication with the orientation detector and the actuator, the controller being configured to be operable to generate at least one instruction for operating the actuator for moving the electromagnetic field sensor into a predefined orientation, in dependence upon the output from the orientation detector.

A metal detector for buried and abandoned chemical weapons is provided, comprising: a transmitting circuit to transmit a detection signal; a frequency selection unit electrically connected to the transmitting circuit and configured to regulate a frequency of the detection signal; a receiving circuit to receive a reflected signal returned from the substance detected; an analog-digital conversion unit electrically connected to the receiving circuit and configured to convert the reflected signal into a digital signal; and a control unit electrically connected to the analog-digital conversion unit. In the present disclosure, the frequency of the detection signal can be regulated by changing a current frequency of the transmitting circuit, so that several forms of iron compound can be detected, thereby increasing the detection accuracy of the ACWs.

A system for near-surface geophysical subsurface imaging for detecting and characterizing subsurface heterogeneities comprises an instrument that outputs probing electromagnetic signals through a ground surface that interact and are affected by scattered signals of acoustic waves that travel through the ground surface and further senses vibrational modes of a subsurface below the ground surface; an imaging device that dynamically generates a time sequence of images of properties of the acoustic waves and maps elastic wave fields of the acoustic waves; and a processor that analyzes dynamic multi-wave data of the images to quantify spatial variations in the mechanical and viscoelastic properties of the subsurface.

A geophysical surveying method and assembly applying transient pulses of electric current to an airborne time-domain electromagnetic transmitter to generate a primary controlled electromagnetic field; measuring, using an airborne receiver, a secondary controlled electromagnetic field to generate controlled field data; measuring, using the airborne receiver, a magnetic component of a natural electromagnetic field at an above-ground position to generate first natural field data; measuring, using a ground receiver at a ground station, telluric electrical currents induced by the natural electromagnetic field and/or a magnetic component of the natural electromagnetic field at a ground position to generate second natural field data; merging the first natural field data and the second natural field data into combined natural field data; extracting, from the combined natural field data, off-time natural field data recorded between the pulses; and generating geophysical survey data based on the controlled field data and the off-time natural field data.

A method and apparatus for offshore electromagnetic surveying for the purpose of hydrocarbon exploration and detection is described. The method comprises the step of A) measuring a measurement vector u between receiver electrodes, where the measurement vector u comprises a plurality of measurement signals u.sub.i, being dependent on a geological characteristic m.sub.k at an geological parameter index k providing information about the geological structure of the geological target area. The method is further characterized in that it also comprises the following steps: B) calculating a transformed vector v as a function of the measurement vector u, where said transformed vector v is designed to optimize the sensitivity to changes in the geological characteristic m.sub.k and C) performing, for each time t, at least one of minimizing uncertainty v(k,t) of the transformed vector v with respect to the geological characteristic m.sub.k, where said uncertainty v(k,t) comprises a non-systematic uncertainty v(k,t) and a systematic uncertainty .sub.wdv(k,t), maximizing a target response v(k,t)/m.sub.k of the transformed vector v with respect to the geological characteristic m.sub.k and minimizing a ratio (k,t) between at least the square of the non-systematic uncertainty <v(k,t).sup.2> of the transformed vector v and the square of the target response (v(k,t)/m.sub.k).sup.2 of the transformed vector v with respect to the geological characteristic m.sub.k.

A calibration method includes determining calibration standards for a reference tool including a reference transmitter and a reference receiver. First and second calibration factors are measured to match a receiver on an electromagnetic measurement tool (the tool to be calibrated) to the reference receiver and to match a transmitter on the electromagnetic measurement tool to the reference transmitter. The electromagnetic measurement tool is deployed in a subterranean wellbore and used to make electromagnetic measurements therein. The measured first and second calibration factors and at least one of the calibration standards are applied to at least one of the electromagnetic measurements to compute a gain calibrated electromagnetic measurement.

An electromagnetic sensitive fiber optic sensor, including a cylinder portion with a hole through the center, where a surface of the cylinder portion includes a magnetostrictive material, and a fiber cable threaded through the cylinder portion and wrapped around the cylinder portion multiple times. In another embodiment, a mandrel surrounds a magnetorestrictive or piezoelectric material and the fiber cable is wrapped around the mandrel.

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.

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.

A geophysical surveying method and assembly applying transient pulses of electric current to an airborne time-domain electromagnetic transmitter to generate a primary controlled electromagnetic field; measuring, using an airborne receiver, a secondary controlled electromagnetic field to generate controlled field data; measuring, using the airborne receiver, a magnetic component of a natural electromagnetic field at an above-ground position to generate first natural field data; measuring, using a ground receiver at a ground station, telluric electrical currents induced by the natural electromagnetic field and/or a magnetic component of the natural electromagnetic field at a ground position to generate second natural field data; merging the first natural field data and the second natural field data into combined natural field data; extracting, from the combined natural field data, off-time natural field data recorded between the pulses; and generating geophysical survey data based on the controlled field data and the off-time natural field data.