Abstract: A system is provided for detecting minerals and metal-containing materials which are located in sediment deposits on the sea floor and which exhibit an induced polarization response. A streamer cable, which, in use, is towed in the sea behind a ship, includes a series of transmitters and receivers at the free end thereof. The cable is towed such that the free end is in contact with to the sea floor and the transmitters are used to transmit a square wave electrical current into the sediment there. The receivers are used to detect any secondary signals produced by an induced polarization source located on or beneath the sea floor in response to electrical current. Pre-amplifiers connected to the receivers provide noise rejection. On-board electronics process the secondary signals to determine measurement parameters characteristic of the source thereof so as to identify the source.

Abstract: A method is provided for detecting minerals and metal-containing materials which are located in sediment deposits on the sea floor and which exhibit an induced polarization response. In this method, a streamer cable is towed in the sea behind a ship. The cable has transmitters and receivers at the free end thereof and the cable is towed such that this free end is close to or trenches into the sea floor. The transmitters are used to transmit a square wave electrical current into the sediment of the sea floor while the receivers are used detect to any secondary signals produced by an induced polarization source located on or in the sea floor in response to the electrical current. The secondary signals are processed to determine measurement parameters characteristic of the source of the secondary signals so as to identify the source and using simultaneously acquired global positional data, to determine the location of the source.

Abstract: A method of imaging an object contained in a medium, having a specific impedance which is different from the specific impedance of the medium, comprising applying current to the medium at various locations at a surface of the medium, extracting current at other locations, detecting voltages produced by the current which has passed through the medium from the surface of the medium at various other locations, successively determining a location and shape and conductivity of the object with increasing accuracy by processing values of the detected voltages, determining a region in the medium in which the object is located from values of the detected voltages which are within upper and lower threshold values, applying acceleration procedures to the conductivities within the region in the course of iterative refinement of these values in the course of an imaging procedure, subsequently restricting further determination of the location of the object with increasing accuracy to voltages obtained from the region of th

Abstract: The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.

Abstract: When prospecting for geological formations, a feeding electrode 2 is grounded in the center of a circle formed by uniformly grounded feeding electrodes 3. The feeding electrodes 3 are connected by lengths of supply lines 4 to current generators 1 via regulators 5. A first stage of investigations involves a preliminary sounding. Current pulses are applied from the generators 1 to the lengths of supply lines 4 which are connected to diametrically opposite feeding electrodes 3. A current pulse period is synchronized with a reference signal received by a receiver 7 from the global radio navigation system. Upon turning the current off, a signal of a field magnetic component transient is measured by a meter 8 that is coupled to a magnetic component sensor 9.

Abstract: An electrical resistance tomography method using steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes.

Abstract: An electromagnetic method is disclosed that can be used to map, track, and monitor subsurface water or solutions and related geologic structure including: groundwater, groundwater channels, groundwater structures, subsurface pollution plumes, locate the source of springs or seeps, map interconnected fracture or porous zones, map leaks in earthen dams, map leaks in drain fields, monitor changes in subsurface water flow, monitor changes in ion concentration in groundwater, monitor in situ leaching solution, monitor movement of heap leaching solutions, monitor changes in subsurface redox or reaction fronts, monitor underground chemical reactions, monitor subterranean bioreactions, or other subsurface waters and related geologic structures. An electric current is injected directly into the water or solution that is to be mapped, tracked, or monitored. It is also necessary to provide a return path for the injected electrical current.

Abstract: Apparatus and method for monitoring a fluid reservoir traversed by at least one well comprising the placing of at least one electrode communicating to the surface and fixed in permanent manner in the well. Hydraulically isolating the section of the well in which it is located from the rest of the well and providing electrical coupling between the electrode and the reservoir. Subsequently, a current is passed through the reservoir; and an electrical parameter is measured, whereby a characteristic representative of the reservoir can be deduced.

Abstract: The measurement equipment serves to map the subsurface geology in a terrain by means of electrical profiling. A plurality of drag electrodes are used for this purpose, the electrodes with specific mutual spacing, being hooked together with a tow in the form of, e.g., a rope or a wire which is towed by a towing means. An electrical current which is so low as to constitute no danger to operators, is transmitted into the earth through the current electrodes and the voltage is measured across the voltage electrodes. A single-ended electrode amplifier is incorporated into each of the voltage electrodes. The method is useful for rapid and detailed mapping of deposits of natural resources, moist site areas, sand and clay localities in connection with road construction and building land as well as water magazines and refuse dumps.

Abstract: A method for monitoring an area of the surface of the earth uses measurement probes arranged in a grid for determining the self-potential with respect to a base probe. The measurement probes are interrogated repeatedly. The earth resistance between measurement probes and the base probe is also measured repeatedly between measurements of self-potential. Potentials on the surface of an area of the earth can be determined precisely, independently of earth-resistance changes.

Abstract: A method of determining the resistivity of an underground formation surrounding a cased borehole including the steps of: a) passing a current along a first pan of the casing and measuring the voltage; b) passing a current along a second part of the casing and measuring the voltage, the second part being spaced from the first part by an intermediate region; c) measuring voltages between the first part of the casing and a point in the intermediate region and between the second part of the casing and the same point; and d) using the measured voltages to derive the resistivity of the formation.

Abstract: An apparatus and method is provided whereby a small diameter, single conductor wireline is combined with standard slick line equipment to obtain "real-time" surface display from well logging tools. A helically formed, insulated conductor coextending within a conductive tube functionally replaces standard solid wire for lowering tools down into a wellbore and for transmitting tool-generated signals to a surface-located display.

Abstract: This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen.

Abstract: A method for borehole compensation using a single transmitter measurement electromagnetic propagation tool is disclosed. Phase shift and attenuation are measured at each of three positions relative to a measurement depth. The measurements are used to calculate borehole compensation. The method may be used for other single transmitter tools and provides more accurate formation measurement in boreholes having high rugosity and washouts.

Abstract: A method and apparatus for monitoring and locating the presence of fluids beyond a containment vessel. A multiplicity of plates having conductive affinity are strategically oriented adjacent the area of liquid storage and periodic surveillance relying on conductivity of the substrate within which the electrodes have been placed are made such that disturbances in the conductivity correlates with migration of fluid being contained. The method and apparatus may be utilized to detect migration of salinated fluids into a region where previously less salination existed.

Abstract: A system of leak detection in an impoundment including a first impoundment layer containing a brine solution, a second impoundment layer positioned beneath the first impoundment layer and having a brine-filled space therebetween, a first electrode positioned in the brine-filled space, an injection electrode positioned in the brine solution on the first impoundment layer, a plurality of sensor elements extending outwardly from the injection electrode for measuring electrical potentials at points distal the injection electrode, and a source of power electrically connected to the first electrode and to the injection electrode for passing a current between the electrodes. A probe assembly is connected to the injection electrode for supporting the injection electrode above the first impoundment layer. The sensor elements are arranged generally coplanar to the injection electrode. Each of the sensor elements are separated by an equal distance from an adjacent sensor element.

Abstract: Method and apparatus for measuring apparent earth resistivity, by determining potential drop produced by electric current injected into the ground. Periodic, or very low frequency polarity reversal of direct current is used to eliminate induced voltage errors that might otherwise occur with higher frequency polarity reversal or alternating current. Synchronizing pulses are used to gather and separately store information from each half cycle. A calibrated readout is obtained in which values of the voltages in the two half-cycles are algebraically subtracted and divided by two to measure the potential drop, with automatic compensation for effects of earth currents.

Abstract: Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.

Abstract: Grounding of poles in a power distribution system is checked by disconnection of the ground wire from the buried grounding conductor (rod) and measurement of the reference ground by conventional techniques. If necessary the grounding conductor is enlarged to lower ground resistance to an acceptable level between 5 and 10 ohms. A pulse generator is then connected between the grounding conductor and the ground lead at the reference pole to generate and transmit through the system netural wire a pulse, preferably on the order of 5 kHz to simulate lightning strikes on the systme neutral. Adjacent poles are then checked one at a time using a current type pickup with peak detector equipment. It is necessary to disconnect the ground wire from the ground connector. A first value is obtained by checking the effects of a pulse in the neutral wire of the distribution system adjacent the selected pole and the output is adjusted by a potentiometer to read 100.

Abstract: A method for reducing noise in electromagnetic geophysical exploration data simultaneously measures three orthogonal components of the ambient noise to produce noise records and simultaneously measures three orthogonal components of the decay of current induced into the earth to produce response records. In measuring the records, the receiving antenna is positioned near the electromagnetic center of the transmitting antenna, whereby the maximum component of the induced current decay signal is vertical or perpendicular to the strata in the earth. The impulse response of the earth is determined from the noise records. The noise portion of the vertical response record is determined from the impulse response and the non-vertical response records, whereby the noise portion is removed from the vertical response record.

Abstract: A method and apparatus for collecting measurements on the surface of the earth in a form which can be processed to obtain enhanced resolution of subsurface resistivity anomalies in the earth's geologic structure. The system of the preferred embodiment utilizes many separately acquired voltage and current measurements on the earth's surface in a superposition analysis to "synthesize" the condition whereby the many separate measurements are acquired simultaneously to give useful advantages in improved depth of investigation commonly known as focused resistivity measurements.

Abstract: An electromagnetic survey method for geophysical exploration, in which the variations in the earth's magnetic field are measured in two, non-parallel directions at one point in the survey area. Simultaneously, the variations in the earth's electrical field parallel to the survey line are measured at a number of points along the survey line. These measured variations are transformed to the frequency domain, and then the horizontal component of the magnetic field orthogonal to the direction of the measured electrical field is calculated. The impedance at each measurement point on the survey line is calculated as a function of frequency, and weighted averages of the impedance for predetermined frequencies using a zero phase length weight function corresponding to a low pass filter applied to the electric field are used to calculate the subsurface conductivity distribution.

Abstract: An improved method and apparatus for detecting telluric noise information while performing induced polarization prospecting. Telluric noise electrodes are positioned on an equipotential line lying about an input current electrode forming part of a conventional IP electrode spread. The telluric noise record obtained from the noise electrodes is essentially free of IP input signal waveform.

Abstract: A geophysical exploration system uses a single conductor cable connected to a current source, the cable having a number of earth probes coupled to it at spaced points with addressable switching units. The switching units are activated in sequence so that the probes inject current into the earth. At locations spaced from the probes the resistivity is measured and recorded for each injection. Resistivity measurements are compared with anomaly models to find a match of patterns, indicating the presence, size and location of an anomaly.

Abstract: A method and apparatus for electromagnetic hydrocarbon exploration which is accomplished by implanting at least two pairs of electrodes into the ground. One pair transmits a signal into the earth, and the other pair receives the signal. With proper processing the polarization and resistivity of the ground can be calculated. The components are arranged in a manner to insure that the electromagnetic coupling can be determined and can be removed from the measurements. Electrode spacing can be varied to focus on the anomalous stratum. If an anomalous stratum is discovered, it is cored to determine the nature of the material creating the anomaly.

Abstract: In electrical geophysical prospecting and in well-logging, in which potential is applied to the earth to cause direct current (or low frequency alternating current) to flow between spaced electrodes and the potential is measured between other electrodes contacting the earth, difficulties are experienced due to the electrode chemistry at the electrode contacts with the earth. This phenomenon is usually called polarization, with spontaneous, usually varying potential being generated at the electrode contact. I have found it possible to use pairs of relatively closely spaced solid conductor electrodes instead of the individual electrodes formerly used, applying an alternating voltage between the two electrodes of each pair which minimizes polarization, and coupling the direct or low frequency A.C.

Abstract: A method of locating a deep well casing at substantial distances below the earth's surface, and for directing the drilling of a second relief well to intersect the first well at substantial distances below the earth's surface is disclosed. A low frequency alternating electric current flow is produced in the casing of the well to be detected by means of current injected into the earth surrounding the first well. The current flow in the casing produces a magnetic field which is detectable by a sensitive magnetic field sensor suspended in the relief hole and spaced a substantial distance from the current source. The magnetic field sensor detects the magnitude and apparent direction of the alternating field, and this measurement is combined with a concurrent measurement of the earth's magnetic field to determine the direction and distance of the casing from the relief well.

Abstract: A method is provided for evaluation of shallow electrical anomalies to determine which are likely to be caused by seepage from a hydrocarbon reservoir at depth. The method involves geochemical lithological, and petrographic analyses of anomalous sediments to determine whether these sediments contain certain features characteristic of seepage-induced anomalies. These features include the following:(1) accumulations of seeped (non-indigenous) hydrocarbons;(2) accumulations of carbonate cements that have .delta..sup.13 C values between -10 and -58.degree./oo;(3) pyrite accumulations in a shallow, porous host rock where the pyrite is distributed within fractures or between original grains with a disseminated or cement-like texture, and where it is not associated with kerogen or coal and is not framboidal in morphology;(4) close proximity of said pyrite and carbonate accumulations; and(50 anomalous (high) induced polarization (I.P.

Abstract: The invention concerns electrical prospecting of the subsoil. According to the invention, electrical prospecting is performed with either continuous or alternating current by using a drilling tubing as at leasts one of two lineal exciter electrodes. The profile of apparent resistivity thus obtained gives a very definite indication of the presence of deep anomalies, even those situated under high resistivity layers or masks, which is frequently the case in the search for deposits. Comparing the real resistivity profile with the theoretical curve obtained from a preliminary model, the extent of the deposit can be determined. The invention applies principally to petroleum, mineral or geothermal exploration.

Abstract: The apparent electrical resistivities of various parts of a marine bottom are determined by supplying an alternating electrical current to a pair of current supply electrodes and measuring potential differences between pairs of measuring locations. The locations are on a straight line on the marine bottom. There is a fixed ratio between the distance between the locations of each pair and the distance between said pair and the pair of current supply locations. Adjoining pairs of measuring locations have a measuring location in common.A flexible cable for taking these measurements is described.The determined resistivities are subsequently compared with calculated resistivities to determine the compositions and thicknesses of the soil layers of the marine bottom.

Abstract: A method of electrically investigating the underground condition by measuring the apparent resistivity in the ground, in which the entire ground region to be investigated is assumed to be an aggregate of a plurality of unit blocks, and the resistivity of each of such unit blocks is analyzed from the measured apparent resistivity thereof to determine the underground condition.

Abstract: A method and apparatus for electromagnetic hydrocarbon exploration which is accomplished by implanting at least two pairs of electrodes into the ground. One pair transmits a signal into the earth, and the other pair receives the signal. With proper processing the polarization and resistivity of the ground can be calculated. The components are arranged in a manner to insure that the electromagnetic coupling can be determined and can be removed from the measurements. Electrode spacing can be varied to focus on the anomalous stratum. If an anomalous stratum is discovered, it is cored to determine the nature of the material creating the anomaly.