Abstract: A method for interpreting transient electromagnetic survey data includes measuring transient response of a medium over a plurality of switching events. The measured transient response to a first one of the current switching events is modeled. Transient response to the model for at least one current switching event prior in time to the at least a first current switching event is calculated. The calculated transient response is summed with the first event measured response and the sum is compared to the electromagnetic survey measurements. The model is adjusted and the calculating summed transient responses is repeated until a difference between the summed calculated responses and the survey measurements falls below a selected threshold.

Abstract: Body (22) for measuring the resistivity of a formation (9) surrounding a well (10) equipped with a lining (11), comprising: a body (23) of a probe (22), a set of three primary voltage measurement electrodes (ea, eb, ec), an upper electrode (ea) and a lower electrode (ec) and a central electrode (eb), two electrodes (In1, In2), an upper current injection electrode (In1) and a lower current injection electrode (In2) arranged on each side of the set of primary electrodes, characterized in that it also comprises, two secondary voltage measurement electrodes (24, 26) arranged on each side of the set of primary electrodes (ea, eb, ec), and between the two current injection electrodes (In1, In2), the spacing between a secondary electrode (24, 26) and the closest primary end electrode (ea, ec) being more than 1.5 times the spacing between the primary electrodes (ea, eb, ec).

Abstract: A marine measurement system is disclosed for obtaining measurements in an underwater operating environment. The system includes a base structure having a top surface, a bottom surface, and cavities provided therebetween. The cavities are also open to the top surface. The measurement system further includes measurement equipment (e.g., electronic equipment and/or instrumentation), which are retained in the cavities. A diaphragm membrane is applied adjacent the top surface and seals the cavities. The diaphragm member is positioned in pressure communication with the operating environment. Furthermore, the cavities are defined by the membrane and the base structure and filled with a pressure compensating fluid that is in pressure communication with the operating environment through the diaphragm membrane.

Abstract: The method for predicting seismic events includes supplying electricity by means of a detection unit (3) fitted with current electrodes (A, B) and potential probes (M, N) arranged in the ground and detecting electrical current and induced potentials by means of said electrodes (A, B) and said reception probes (M, N), for the calculation of resistivity in the ground. The resistivity data recorded is acquired and stored and then transferred to a means of analysis and processing (11). Finally, resistive drops in relation to preset values, corresponding to the approach of seismic events are evaluated.

Abstract: A system for mapping electrical conductivity of the seafloor incorporates a plurality of data logging units, where each unit (100) is an assembly adapted for deployment at a location on the seafloor for measurement of horizontal electric and magnetic fields. Rigidly attached and extending vertically from the unit assembly is a vertically-oriented substantially rigid arm (158) having a pair of vertically-displaced electrodes (160, 162) disposed on the arm to create a vertically-oriented dipole antenna. The electrodes are in electrical communication with an amplifier located within the assembly which generates an amplified signal which is then provided to a data logging processor also located within the assembly. The processor collects time series of amplified electric field and magnetic signals over a predetermined period of time.

Abstract: A subsurface imaging cable includes a plurality of sensor modules, wherein the plurality of the sensor modules are flexible and each of the plurality of the sensor modules is spaced apart on the subsurface imaging cable at a selected distance; and a flexible medium connecting the plurality of the sensor modules, wherein the subsurface imaging cable is flexible and adapted to be wound on a reel. A method for subsurface images includes acquiring direct-current measurements at a plurality of sites in a survey area; acquiring a first set of electric and magnetic measurements from natural electromagnetic fields at the plurality of sites; acquiring a second set of electric and magnetic measurements using controlled electric and magnetic sources at the plurality of sites; and determining a subsurface conductivity distribution from the direct-current measurements and the first set and the second set of electric and magnetic measurements.

Abstract: A method for processing magnetotelluric signals to identify subterranean deposits is provided for. The methods comprise obtaining magnetotelluric data from an area of interest. The magnetotelluric data comprises the amplitude of magnetotelluric signals recorded over time at one or more defined locations in the area of interest. The data for each location then is filtered through a set of frequency filters. The frequency filters correspond to subterranean depths over a range of interest. Amplitude peaks in the filtered data then are identified and analyzed to determine a value correlated to the resistance of the earth at each frequency and location. The resistance values are indicative of the presence or absence of deposits at the corresponding subterranean depth.

Abstract: A passive geophysical prospecting method and apparatus are provided. The apparatus has an antenna for detecting electromagnetic radiation naturally emanating from the Earth's surface and generating an electrical signal from the detected electromagnetic radiation while traversing the Earth's surface by a vehicle traveling over land or water or in an airplane. The electrical signal is filtered of frequencies below 65 Hz, preferably above 100 Hz and more preferably below 800 Hz, and above 12,000 Hz, preferably above 8,000 Hz, to generate a filtered signal. The filtered signal is converted to a prospecting voltage signal. The prospecting voltage signal is then compared to a set voltage and a difference signal is generated, recorded and analyzed.

Abstract: A sea-floor electromagnetic measurement device for obtaining underwater measurements of earth formations including a central structure and arms attached to the central structure so that they can pivot relative to the central structure. An electrode is attached to the end of each of the arms or to the central structure, and/or magnetometers are attached to the arms. A method for undertaking sea-floor electromagnetic measurements of earth formations including measuring electric fields at a selected distance from a central structure of an electromagnetic measurement system. Magnetic fields are then measured at the same location.

Abstract: A geophysical prospecting method and apparatus that utilizes the harmonics and sub harmonics waves induced into the earth by the electric power grid. The amplitude-frequency data are converted to amplitude-depth data and further converted to a differential curve. The resulting differential curve is compared to known patterns of the interested geological features, such as hydrocarbon reservoir, to identify whether the features exist and at what depth such geological features lie.

Abstract: The present invention is for a precision grid surveyor having a stationary unit and a roving unit. The stationary unit has a light source unit that emits a light beam and a rotator to project the light beam toward detectors on a roving unit. The roving unit moves over an area to be surveyed. Further the invention is for a method of mapping details of hidden underground iron pipelines, and more particularly the location of bell joints.

Abstract: A subsurface imaging cable includes a plurality of sensor modules, wherein the plurality of the sensor modules are flexible and each of the plurality of the sensor modules is spaced apart on the subsurface imaging cable at a selected distance; and a flexible medium connecting the plurality of the sensor modules, wherein the subsurface imaging cable is flexible and adapted to be wound on a reel. A method for subsurface images includes acquiring direct-current measurements at a plurality of sites in a survey area; acquiring a first set of electric and magnetic measurements from natural electromagnetic fields at the plurality of sites; acquiring a second set of electric and magnetic measurements using controlled electric and magnetic sources at the plurality of sites; and determining a subsurface conductivity distribution from the direct-current measurements and the first set and the second set of electric and magnetic measurements.

Abstract: An instrument for geophysical measurement of magnetic field strength, using a GMR sensor is provided. The instrument achieves high sensitivity across a relatively wide bandwidth in an instrument which is small and lightweight. The instrument makes it feasible to obtain data, substantially simultaneously, at a plurality of locations and/or frequencies, thus not only reducing time requirements involved in measurements but reducing or eliminating the need for correcting data for changes in earth's magnetic fields. The instrument has relatively high vector sensitivity and relatively low power consumption.

Abstract: A method of cathodic current optimization measures drill stem resistances along a well hole being drilled, correlates the drill stem resistances to respective types of underground formations at corresponding positions along the well hole, predicts a respective position of at least one anodic area on a well casing to be installed and determines an amount of cathodic current to be applied thereto.

Abstract: A sensor and method for measuring an electrical potential difference are described. The sensor includes a micro-fabricated field emission device situated in a space plasma environment. The field emission device has an emitter terminal and a gate terminal. A voltage source applies a voltage across the gate and the emitter terminals to induce current to flow from the emitter terminal A first current monitor measures current flowing from the emitter in response to the applied voltage. A second current monitor measures current flowing to the gate. A control system correlates applied voltages and measured gate and emitter currents with electrical potential differences between the field emission device and the space plasma environment. The control system obtains the gate and emitter currents from the current monitors. A processor computes a value from the gate and emitter current measurements based on a predetermined functional relationship.

Abstract: Apparatus for determining the distribution of the electric polarization of a vessel in water, comprises an array of electric potential sensors (22) which are located in the water beneath the vessel and each generates a signal corresponding to the amplitude of the electric potential at the sensor as effected by the vessel, a signal processor unit (48) and cables (42) connecting each sensor (22) to the signal processor unit (48) to deliver each respective signal to the signal processor unit, the signal processor unit (48) serving to determine the potential difference between respective pairs of sensors (22) from the respective signals they generate, and the signal processor unit (48) processing multiple such potential difference determinations to deduce the distribution of electric polarization in the vessel which would cause said electric potential at each of the electric potential sensors (22).

Abstract: An apparatus and method for passively determining physical characteristics of subterranean geological formation which for example bear oil or gas or commercial important ore deposits such as precious metals. The apparatus includes an antenna for acquiring low frequency signals naturally emanating from the earth. The received signal is first put through a low pass filter and buffer and then converted from analog to digital, stored in a memory buffer, converted to a frequency spectrum by a Fourier transform, and then further processed to display geophysical information versus the depth of such discontinuities.

Abstract: A method for determing the potential in a three-dimensional domain containing a source domain of source particles and a target domain of target particles involves assigning the source particles into source particle clusters and the target particles into target particle clusters, assigning a collection point to each of the clusters, and determing the inverse distance from each particle to the collection point of its respective cluster. A pseudo-particle representative of each particle within the cluster is defined at the collection point of each cluster in accordance with the determined inverse distances and the charge-like measure of each of the particles. The potential, and/or its gradient, at any of the target particles is then determined from the position and the charge-like measure of the associated pseudo-particle.

Abstract: An apparatus and method for passively determining the depth and thickness of a subterranean geologic formation bearing hydrocarbons, e.g., oil and/or gas, or commercially important ore deposits, e.g., precious metals. The apparatus has an antenna to pick up extremely low frequency signals naturally emanating from the Earth's surface. In a preferred embodiment, the received signal is amplified and filtered. The signal is then modulated onto a carrier wave. The modulated signal is then filtered to eliminate one of the sidebands, for example, the lower sideband. An oscillator generates a tuning frequency which is then beat against the filtered, modulated signal in order to tune to a particular frequency. The oscillator sweeps through the range of frequencies, e.g., in the upper sideband portion of the filtered, modulated signal.

Abstract: An instrument for geophysical measurement of magnetic field strength, using a GMR sensor is provided. The instrument achieves high sensitivity across a relatively wide bandwidth in an instrument which is small and lightweight. The instrument makes it feasible to obtain data, substantially simultaneously, at a plurality of locations and/or frequencies, thus not only reducing time requirements involved in measurements but reducing or eliminating the need for correcting data for changes in earth's magnetic fields. The instrument has relatively high vector sensitivity and relatively low power consumption.

Abstract: An apparatus for measuring the vertical component of the gradient of the electrical field of the soil surface includes two electrodes. Each electrode includes a capacitor with a semiconductor layer.

Abstract: The present invention relates to realize a tectonic activity monitoring equipment providing apparatus and method to detect a feeble electromagnetic wave occurred by the tectonic activity with a high signal-to-noise ratio (S/N) and to predict earthquake and volcano eruption. The apparatus and the method for monitoring tectonic activity of the present invention comprises electromagnetic wave sensors and one or more of amplifiers for amplifying signals detected by the sensors. And an observation frequency for detecting electromagnetic wave occurred from tectonic activity is set to a frequency between a few tens Hz and 1 kHz so as to eliminate the influence of noises of a strong radiation power less than a few tens Hz and tropical thunder noises of more than 1 kHz of higher order modes propagating between the earth and the ionosphere.

Abstract: An apparatus and a method for predicting an earthquake are disclosed. The apparatus employs a set of two electrodes for measuring the vertical component of the gradient of the electrical field due to the capillary movement and the surface evaporation of the ground water, a humidity sensor for measuring the humidity of the soil surface, and a temperature sensor for measuring the temperature of the soil surface. The correlation coefficient between the changes in the electrical field gradient due to changes in the surface temperature related to the water evaporation from the soil surface is calculated. The correlation coefficient changes its sign at the time of appearance of the earthquake precursor.

Abstract: An apparatus and method for passively determining the depth and thickness of a subterranean geologic formation bearing hydrocarbons, e.g., oil and/or gas, or commercially important ore deposits, e.g., precious metals. The apparatus has an antenna to pick up extremely low frequency signals naturally emanating from the Earth's surface. In a preferred embodiment, the received signal is amplified and filtered. The signal is then modulated onto a carrier wave. The modulated signal is then filtered to eliminate one of the sidebands, for example, the lower sideband. An oscillator generates a tuning frequency which is then beat against the filtered, modulated signal in order to tune to a particular frequency. The oscillator sweeps through the range of frequencies, e.g., in the upper sideband portion of the filtered, modulated signal.

Abstract: A seismic electromagnetic field signal is detected at each of observation stations installed at at least two places, and civil noise and atmospheric discharge noise are eliminated from the signal to obtain a low-frequency seismic electromagnetic field signal O.sub.s. A local characteristic signal C.sub.e and a refined local characteristic signal C.sub.f are obtained by processing the signal O.sub.s. The signals O.sub.s, C.sub.e and C.sub.f are transmitted to a central station. At the central station, a delay time T and a half-width H are obtained from the cross-correlation function between the observation stations, and further a regional characteristic signal C.sub.r is obtained from the seismic electromagnetic field signal O.sub.s. An earthquake source region distribution, an earthquake magnitude, and earthquake occurrence time are estimated on the basis of the signals obtained at the central station and the local characteristic signal C.sub.e and refined local characteristic signal C.sub.

Abstract: A surface-mounted pH sensor provides continuous pH profiling with depth during standard cone penetration testing (CPT). The pH sensor includes at least two electrodes, one being an antimony electrode and the other being a ceramic electrode. The electrodes are mounted to the shaft of a cone penetration device, and make contact with underground fluids during CPT. The antimony electrode, which functions as a measurement electrode, creates an exchange equilibrium between the hydrogen ions in the underground fluids and the ions of the antimony. This equilibrium creates a potential in the antimony electrode which is measured against the stable reference potential of the ceramic electrode. The resulting potential difference is indicative of the pH level of the underground fluids.

Abstract: A system is provided for locating and delineating sea floor occurrences of petroleum seepage, achieved by apparatus for the detection of the resulting abnormal distribution of electrical potential within the affected sediments. The system uses an electrically insulating probe, deployed by steel cable from a ship, for the implantation of numerous electrodes within the sediment at depths between 60 cm and 5 m. Insulated conductors within the probe connect the electrodes to a reference electrode by way of an electrometer which facilitates measurement of the difference in electrical potential between any one of the probe electrodes and the reference electrode. Digital measurements are conducted to an associated acoustic modem and thence to the ship through the water. The system allows rapid assessments of sedimentary electrical conditions over large areas of seafloor by the repeated introduction, utilization, withdrawal, and relocation of the probe.

Abstract: The apparatus includes a pair of electrodes which makes it possible to channel a current density creating the current which induces a magnetic field in one or more induction coils. This magnetic field is measured with the aid of one or more magnetometric transducers. The electric/magnetic transfer rate of the coils and the conductivity of the conductive medium are known, so that the value of the electric field is deduced on the basis of Ohm's law. The local magnetic field is previously measured so as to take account thereof when measuring the induced magnetic field.

Abstract: A method for producing electrochemical impedance spectra. Spontaneously occuring coupling current noise between an array of electrodes which may be of substantially the same material is detected. A time domain record of the detected current noise is stored and the time domain record of the detected current noise is transformed to the frequency domain. Spontaneously occurring potential noise between the array of electrodes and a further electrode is detected. A time domain record of the detected potential noise is stored and the time domain record of the detected potential noise is transformed to the frequency domain. The frequency domain current noise and potential noise transformations are then transformed to the impedance domain to produce the required electrochemical impedance spectra.

Abstract: An apparatus for measuring transient earth current includes a detection electrode and a second electrode disposed beneath the surface of the earth in vertical alignment with one another at depths greater than those to which electromagnetic waves generated above the surface of the earth having commercial power line frequencies penetrate, such that the electrical resistance between the detection electrode and the second electrode is on the order of several tens of thousands of ohms, and a charge detector for detecting only high frequency components of a current flowing between the detection electrode and the second electrode. On the basis of these detected high frequency components, the likelihood of an occurance of an earthquake may be determined.

Abstract: A method is provided to monitor specific filtration resistance, total drainage resistance and drainage flow rate in a continuous on-line manner in the paper making process. It can be combined with the simultaneous measurement of streaming potential or zeta potential so as to enable optimization of the chemistry of the papermaking process.

Abstract: A method and apparatus for passively determining the depth of an anomaly using means for monitoring a broad spectrum of frequencies and analyzing the amplitude and modulation of a time and/or location varying signal within discrete bands of frequencies to determine the depth of a spatial or temporal anomaly. A means for recording and mapping substerranean features based on an ascending or descending sequence of frequency measurements is also disclosed.

Abstract: An apparatus for sensing the electrical potential of a positive electrostatic field which is primarily below the surface of the earth, and observing the changes in a series of each reading is accomplished by means of an instrument employing a column of mercury in a small-diametered quartz tube, which is open on its lower end with means connecting to the other end for changing the level of mercury within the tube. A conductive coating on the exterior of the tube is connected to an electrometer and the coating is arranged to be selectively grounded or ungrounded in conjunction with changing the level of the mercury column. The readings for the electrometer provide a measure of the electrostatic field.

Abstract: A method for detecting earthquakes comprises the steps of picking up pre-earthquake long waves or earth currents at four or more observation points located underground or at the sea bottom, carrying out a computation based on the interrelation among the so-obtained= signals to obtain the three-dimensional distribution of the sources and intensities of the long waves or earth currents, and predicting the focal region, scale and time of occurrence of earthquakes from the time-course variation in the so-obtained three-dimensional image of the wave source.

Abstract: The present invention relates to a system for acquisition and separation of the effects of simultaneous sources of electromagnetic field. According to the invention the system comprises an array of n pick-ups (1a . . . 1e) connected to registration means (2), the minimum number n of pick-ups per array being equal to 2s+2, where s is equal to a number of simultaneous sources to be analysed.

Abstract: Apparatus for measuring the interfacial impedance in an electrochemical cell having a pair of electrodes in contact with an electrolyte medium that includes circuitry for measuring the interaction current flowing between the electrodes at a series of predetermined external impedance values and an analyzer for determining the interfacial impedance based on the current measurements.

Abstract: A method and apparatus for locating and evaluating surface and subsurface anomalies by detecting, monitoring or measuring transient or local variations respectively which occur in an alternating component of a vertical current having a frequency characteristic which emanates from the earth'surface in the region being monitored or measured. For locating fixed anomalies, local variations which occur in the amplitude, frequency and frequency modulation of the alternating component of the vertical current are measured. For detecting the passage of moving or transient anomalies, a stationary detector is positioned to detect any change in the vertical alternating current leakage in the vicinity of the detector which is caused by a moving or transient anomaly such as a submerged submarine, seismic activity, or sustained severe wheather. For accuracy enhancement and redundancy, simultaneous measurements of the signal strength in multiple frequency bands may be used.

Abstract: Offshore or onshore electrical surveys of buried or submerged structures such as pipeline are conducted in a fixed-cell-to-moving-cell fashion either before or after one or more established pipe-to-electrolyte potentials can be obtained. The results of the fixed-cell-to-moving-cell survey are then corrected by a summation of the fixed-to-moving-cell recorded potential and the established potential at the location of the established potential to obtain a reliable electrical survey of the structure. As indicated, the fixed-cell-to-moving-cell survey may be conducted either before or after the established potential is obtained or either before or after a disposable wire survey using a direct connection to the structure.

Abstract: At least one string of several spaced measuring probes for the measurement of surface potentials is laid on the surface of the earth in such a manner that several probes are located outside and several probes are located inside the area of the surface over a reservoir. The potentials measured by all probes are polled in a sequence of periodic cycles. The signals from each probe are, during each cycle, filtered to separate higher-frequency changes in the signals from substantially lower-frequency changes in the signals. For the higher-frequency changes in the signals from each probe, an average and/or a sum are determined as a measure of the higher-frequency amplitudes for each probe. The higher-frequency amplitudes for the probes of a string of measuring probes are compared and the location at which the higher-frequency amplitudes for two adjacent probes change abruptly is taken to be the hydrocarbon/water interface in the underground reservoir.

Abstract: A method of electromagnetic geophysical exploration of the earth's subterranean formations wherein an array of magnetometers are deployed at reference sites to obtain a measure of horizontal components of the earth's electromagnetic field and magnetometers are simultaneously deployed at a plurality of exploratory sites within a region of interest to obtain a measure of the vertical component of the earth's electromagnetic field. Resultant correlations of the horizontal and vertical components of the electromagnetic field can provide a multidimensional representation of the earth's resistivity structure.

Abstract: A method of forecasting earthquakes as a function of transient variations in electric earth currents and apparatus for practicing such method. Transient variations in earth currents are detected from electrodes buried in the earth and portions of the transient variations within preselected frequency ranges are selected. The amplitude of such portions are then compared to predetermined standards for predicting magnitude, location and/or time of occurrence of an impendent earthquake.

Abstract: The present invention relates to a wheel electrode suitable for use with a device for making an electrical survey of a structure contained in an electrolyte. The wheel electrode includes a chamber which contains electrolytic solution and a porous rim. The rim includes a dielectric rim structure having at least one recess in its axial surface, a plurality of apertures passing through the rim structure into the recess, and at least one porous member securable in the recess and having a predetermined rate of permeation. A metal electrode is positioned in the chamber in contact with the electrolytic solution. An elastic porous rim cover is securable about the rim for making contact with the electrolyte. The rim cover is adapted to carry an electrically conductive solution to the electrolyte during wheel rotation. Generating mechanisms are spaced about the wheel electrode at predetermined intervals for generating a series of electrical signals as the wheel electrode rotates.

Abstract: In an apparatus or installation having a metal part corroding in an electrolyte contacting the part, that part is a first electrode electrically insulated from a second electrode, for example another part of the apparatus, also contacting the electrolyte. No external electrical power is applied to the electrodes/electrolyte system. The low frequency voltage between the electrodes is observed. This voltage is a low frequency noise signal. Amplitude values of the signal are measured and subjected to an averaging computation yielding data indicating the corrosion rate of the first electrode and the nature of the corrosion.

Abstract: A method for locating and evaluating surface and subsurface anomalies. Solar wind results in a multi-frequency, high energy ionic impingement at the terrestrial poles of the earth. Monitoring the activity of the solar wind allows the determination as to when the activity produces a vertical alternating current leakage (solar alternating current) due to the ionic impingement. When the vertical current leakage is in a proper range which can be measured and which reflects and represents surface and subterranean anomalies, a predetermined region of the earth to be prospected is traversed. Local variations which occur in the amplitude, frequency and frequency modulation of the vertical alternating current leakage due to the ionic impingement of solar winds at the terrestrial poles (solar alternating current) is measured. The measurements are recorded in correlation with the spatial relation to the points of measurement to determine significant measurements indicative of surface and subterranean anomalies.

Abstract: An electrical survey of buried structures such as underwater or underground pipelines utilizes the steps of connecting one end of an economically disposable wire from a wire supply to the structure, either directly or through a heavier lead, the opposite end being electrically connected to a cell. The cell is moved along the structure together with a wire supply and a meter to obtain periodic measured structure-to-electrolyte potential values. If the wire is accidentally or intentionally disconnected during the survey, a stationary electrode is positioned at the wire break or last valid measured reading, such electrode being reconnected to the free end of the wire from the supply. The survey then continues periodically obtaining electrode-to-cell potential values. A structure-to-electrolyte potential profile is obtained by summing the last valid recorded structure-to-electrolyte potential value with each electrode-to-cell values. The summing may be done after the survey is completed by computer.

Abstract: The apparatus and method of the present invention facilitate surveys of buried structures, such as pipelines or the like, in particular by substantially automatically measuring and indicating distance information. Preferably that information is obtained by a transducer that produces serial data representing the length of wire bailed out from a portable reel and a cyclical counter responsive to such data for counting the serial data. A signalling device, such as a horn, strobe light, etc., is activated each time the counter completes a cycle as an indication that a predetermined distance has been covered since the last measurement was made and that the next potential measurement should be made. The number of pulses of such serial data counted in each cycle of the counter can be manually adjusted to obtain small or large distance intervals between test locations at which potential or other measurements are to be made to obtain a substantially continuous survey of the pipeline.

Abstract: A reference cell for conducting closely spaced buried structure-to-soil electrical surveys uses a soil contact cell adapted to be mounted on the lower end of a pole or cane to be held by the surveyor walking over the right-of-way of the buried structure such as an underground pipeline. The cell includes a fluid chamber on the lower end of the pole or cane and includes on the lower end of the chamber a ground contact pad. A spring loaded bottom wall or boot closes the chamber and is operative to reduce the volume of the chamber when the lower end of the chamber is forced by the pole into contact with the ground above the buried structure. The reduction in volume of the chamber forces fluid through the contact pad to the ground to insure good electrical contact. Fluid in the chamber may be continuously replenished by a make-up supply carried by the surveyor which is drawn from the supply by return of the boot to its unstressed state.

Abstract: An apparatus and method of conducting continuous or closely spaced buried structure-to-soil electrical surveys uses a soil contact cell adapted to be worn on the bottom of the walking field boots of a surveyor walking over the right-of-way of the buried structure such as an underground pipeline. The cell is in the form of a sandal which may readily be secured to and removed from the bottom of the boot. The cell includes an impervious upper plate and a pervious lower ground contacting flexible sole plate forming with the upper plate a flat chamber which may be filled with a loose silica sand fill or sponge material. A copper rod or strap is imbedded in the material and electrically connected through a meter carried by the surveyor to the structure through a length of economically disposable wire.

Abstract: In the present invention a method and apparatus for electrical surveys of offshore metal structures includes measuring the electrical potential difference between the structure and an electrolyte, such as sea water and/or the sea bottom, in which the structure is contained. Such measurements are made at roughly approximated recorded distance locations along the structure and the approximate distance information is corrected based on periodically taken accurate distance measurements. Provision is also made to correct data for line currents in the structure, and a method is disclosed for examining the effectiveness of an electrically insulating member connected in the structure. Moreover, an improved insulated wire having minimum insulation holidays and a method for making the same are disclosed.

Abstract: A sample probe for obtaining relatively small subsurface gas samples for analysis during geo-chemical exploration. The probe is comprised of a long slender shaft capable of being driven into the soil and a hammer assembly which mounts to the shaft and is utilized to drive and remove the shaft. The shaft includes a passage for removal of interstitial gas and the passage may be mechanically sealed or opened while the probe is in place in the soil. The probe shaft also includes temperature, soil humidity and soil pH sensors which are utilized to obtain additional parameters to be considered during analysis of the gas samples.