Abstract: Method for assessing hydrocarbon source rock potential of a subsurface region without well log information. The method uses surface electromagnetic (121) and seismic (122) survey data to obtain vertical profiles of resistivity and velocity (123), which are then analyzed in the same way as well log data are analyzed by the well known Delta Log R method (124).

Abstract: A vertical receiver antenna device includes first and second receiving, electrode units interconnected by a receiver antenna cable and connected to means for the electromagnetic surveying of electrically resistive targets potentially containing hydrocarbons. The receiver antenna is arranged in a tubular, non-magnetic antenna housing arranged vertically in subsea uncompacted material, and one of the first and second receiving electrode units being connected in a electrically conductive manner to the underlying structure, and the other one of the first and second receiving electrode units being arranged in a portion of the antenna housing distantly from the first one of first and second receiving electrode units.

Abstract: A device rotates at least one static magnetic field about an axis, producing a rotating magnetic dipole field, and is movable in relation to the surface of the ground. The field is periodically sensed using a receiver to produce a receiver output responsive to the field. A positional relationship between the receiver and the device is monitored using the output. In one aspect, changing the positional relationship, by moving the device nearer to a boring tool which supports the receiver, causes an increase in accuracy of depth determination. In another aspect, determination of an actual overhead position of the boring tool, and its application, are described. Use of a plurality of measurements over at least one-half revolution of each magnet is disclosed. Establishing a surface radial direction toward a boring tool and resolution of multi-valued parameters is described. Calibration techniques, as well as a three transmitter configuration are also described.

Abstract: Location determination is performed using a transmitter including an elongated generally planar loop antenna defining an elongation axis. The elongation axis is positioned along at least a portion of a path. A magnetic field is then generated which approximates a dipole field. Certain characteristics of the magnetic field are then determined at a receiving position radially displaced from the antenna elongation axis. Using the determined certain characteristics, at least one orientation parameter is established which characterizes a positional relationship between the receiving position and the antenna on the path. The magnetic field may be transmitted as a monotone single phase signal. The orientation parameter may be a radial offset and/or an angular orientation between the receiving position and the antenna on the path. The antenna of the transmitter may be inserted into a first borehole to transmit the magnetic field to a receiver inserted into a second borehole.

Abstract: An electromagnetic energy transmitter is provided for borehole to surface electromagnetic (BSEM) surveying. The transmitter is lowered into a well borehole to a desired location in a well borehole to emit electromagnetic energy for the surveys. The transmitter affords more accurate measurements of its position in the well borehole. The transmitter also senses pressure and temperature conditions at its borehole location to provide indications of detected potential problems in the well from the survey or other sources, and to reduce risks and enhance safety and quality of the operations.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method of determining anisotropy in a borehole is disclosed. An array of measurements along the borehole is obtained and a first depth in the borehole is selected. An arbitrary plane oriented with respect to the borehole at the first depth is designated and an anisotropy for the first depth with respect to the arbitrary plane is determined. The arbitrary plane is repositioned at the first depth and an anisotropy for different positions of the arbitrary plane at the first depth is determined. A minimum anisotropy coefficient with respect to the arbitrary plane at the first depth is identified based on anisotropy for different positions of the arbitrary plane. An anisotropy tensor for the first depth is then identified.

Abstract: An apparatus for making directional resistivity measurements of a subterranean formation includes a resistivity tool with a longitudinal axis and an outer surface, a first antenna deployed below the outer surface and having an axial mode coil for processing an axial electromagnetic wave and a transverse mode coil for processing a transverse electromagnetic wave to form a joint-coil structure, a second antenna deployed below the outer surface and spaced at an axial distance from the first antenna, at least two sets of slots with different orientations formed on the outer surface. A corresponding method for making directional resistivity measurements includes rotating a resistivity tool in a borehole, utilizing a transmitter-receiver antenna group formed in the resistivity tool to process a superimposition of the axial and transverse electromagnetic waves, and computing a resistivity-related measurement from the superimposition of the axial and transverse electromagnetic waves received on the receiver antenna.

Abstract: Techniques for surface exploration and monitoring are presented. In representative embodiments, a system is provided that cars perform multiple types of measurements of a surface. For example a single system of survey probes and one or more survey controllers can be used to offer both seismic and electrical measurements. A survey controller can be configured to automatically poll survey probes to obtain identifiers of the probes aid determine a relative order the probes. Survey probes can be configured to; (a) collect signals associated with a surface; (b) digitize the signals to form digital data; and (c) store the digital data for later transmission to the survey controller. Relative positions of survey probes can be automatically determined using a transmitting beacon or other techniques. Survey probes can automatically disconnect from a power conduit while measuring a surface property and operate using an internal source of power when disconnected, to reduce noise.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: An apparatus and method for estimating a parameter of interest of an earth formation involving alignment information between non-collocated oriented receivers and their corresponding non-collocated oriented transmitters. The method may include generating signal responses indicative to energy transmitted into an earth formation; estimating differences in alignment between transmitters and receivers; using the estimated differences in alignment to compensate for misalignment; and estimating a parameter of interest using the misalignment compensated signals. The misalignment estimate may include an inversion of at least one measurement from an alignment sensor. The apparatus may include a bottom hole assembly with oriented transmitters, oriented receivers, one or more alignment sensors, and at least one processor configured to compensate for misalignment using information about difference in alignment between at least one oriented transmitter and at least one oriented receiver.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: Disclosed is an electromagnetic receiver assembly for marine electromagnetic surveying, the electromagnetic receiver assembly comprising an elongated housing and receiver electrodes mounted at separate points along the elongated housing. An embodiment may include an electromagnetic receive assembly that includes an elongated housing, wherein the elongated housing defines an interior chamber. The electromagnetic receiver assembly may further include receiver electrodes configured to be in contact with water when in operation, wherein the receiver electrodes are mounted at separate points along the elongated housing. The electromagnetic receiver assembly may further include sensor electronics disposed in the interior chamber and electrically coupled to the receiver electrodes. The electromagnetic receiver assembly may be configured for deployment on or near a bottom of a body of water.

Abstract: An EM receiver instrument suitable for making underwater electric field measurements. The EM receiver comprises a dipole antenna; an AM modulator for applying modulation to a signal detected by the antenna; a fiber-optic voltage sensor and an application of AM demodulator for applying demodulation to the signal. The fiber-optic sensor may be an interferometric voltage sensor or a phase sensitive voltage sensor.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: Method of determining electrical anisotropy in a subsurface formation, wherein electromagnetic field data from a multi-offset electromagnetic survey obtained by using an electromagnetic source and a plurality of electromagnetic receivers at varying offset distances from the source is provided. The electromagnetic field data comprises a first set of multi-offset response signals received at each receiver with the electromagnetic source emitting at a first frequency, and at least one additional set of multi-offset response signals received at each receiver with the electromagnetic source emitting at a different frequency. The presence of electrical anisotropy in the subsurface formation is determined using the first and at least one additional sets of multi-offset response signals.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: Methods for geophysical surveying include disposing an electromagnetic source and first and second receiver electrodes in water; actuating the source; and detecting a responsive electromagnetic field by measuring a potential difference between the first and second receiver electrodes, wherein: the electromagnetic source defines a source dipole axis; the first and second receiver electrodes define a receiver dipole axis; and the source dipole axis is not substantially parallel to the receiver dipole axis. Systems for geophysical surveying include a first source electrode on a first source cable; a second source electrode on a different second source cable, the first and second source electrodes forming an electromagnetic source and defining a source dipole axis; a first receiver electrode on a first receiver cable; a second receiver electrode on a different second receiver cable, the first and second receiver electrodes defining a receiver dipole axis not substantially parallel to the source dipole axis.

Abstract: The invention relates to instruments designated for geophysical survey, in particular for soil mass exploration using electromagnetic waves. Radio frequency assisted geostructure analyzer comprising transmitting loop (1) and radio transmitter (2) installed on the first pillar (3), receiving antenna and radio receiver (7) installed on the second pillar (9), with receiving antenna consisting of receiving loop (4) and antenna rod (10), and also receiving ferrite antenna (5).

Abstract: A stabilized field sensor apparatus collects field data, in particular magnetic field data, with reduced motion noise. The apparatus includes a tear drop shaped housing, a tow frame in the housing, a plurality of vibration isolating dampers spaced around the frame, a base assembly mounted to the dampers, a support pedestal having a bottom end fixed to the base assembly and an upper free end, a single spherical air bearing connected to the upper free end of the pedestal, an instrument platform with a lower hollow funnel having an upper inside apex supported on the air bearing for a one point support, principal and secondary gyro stabilizers for maintaining pivotal and rotational stability, and at least one field sensor mounted to the instrument platform for collecting the field data while being stabilized against motion noise including vibration, pivoting and rotation from the base assembly, from the tow frame and from the housing.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method for electromagnetic geophysical surveying according to one aspect of the invention includes disposing a plurality of electromagnetic receivers in a selected pattern above an area of the Earth's subsurface to be evaluated. An electromagnetic source is repeatedly actuated proximate the electromagnetic receivers. Signals generated by the receivers, indexed in time with respect to each actuation of the at least one electromagnetic energy source, are recorded. The recorded signals are processed to generate an image corresponding to at least one point in the subsurface. The processing includes stacking recordings from each receiver for a plurality of actuations of the sources and beam steering a response of the receivers such that the at least one point is equivalent to a focal point of a response of the plurality of receivers.

Abstract: A method for removing the effects of an airwave from marine electromagnetic data comprising providing an electromagnetic source and at least one receiver in the water; measuring the electromagnetic response at a first source-receiver separation; determining a scaled version of the airwave response at a source-receiver separation where the earth response is negligible and using the scaled airwave response to determine the earth response measured at the first separation. Using this method, an improved estimate of the earth's response can be achieved.

Abstract: A method for acquisition and processing of marine seismic signals to extract up-going and down- going wave-fields from a seismic energy source includes deploying at least two marine seismic energy sources at different depths in a body of water. These seismic energy sources are actuated with known time delays that are varied from shot record to shot record. Seismic signals from sources deployed at different depths are recorded simultaneously, Seismic energy corresponding to each of the sources is extracted from the recorded seismic signals. Up-going and down-going wave-fields are extracted from the sources deployed at different depths using the extracted seismic energy therefrom. A method includes the separated up-going and down-going wave-fields are propagated to a water surface or a common reference, the up-going or the down-going wave-field is 180 degree phase shifted, and the signals from these modified up-going and down-going wave-fields are summed.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method of monitoring a behavior of carbon dioxide in a stratum by using a marine Controlled-Sources Electromagnetic survey, includes: (S10) collecting a sample of sandstone at a stratum for charging carbon dioxide; (S20) calculating an effective porosity of the collected sample; (S30) measuring an electrical resistivity by saturating the collected rock sample with a pore fluid having a different concentration; (S40) forecasting a change of an electrical resistivity of stratum by charging carbon dioxide; (S50) carrying out a Marine CSEM exploration before and after charging the carbon dioxide separately in each step; and (S60) monitoring a charging behavior of carbon dioxide in stratum by a Marine CSEM exploration.

Abstract: A method of surveying the condition of an underground enclosure including the steps of (a) positioning at least one transmitter/receiver unit (including an antenna) within an underground, substantially nonconductive enclosure, such that a substantial air gap exists between the antenna and the inner wall of the enclosure; (b) transmitting an ultra wideband (UWB) signal toward at least a portion of the inner wall; and (c) processing the return signal in order to identify the interface between the soil and a region of conductivity different from the soil.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A system for underwater communications through a region between a transmit antenna and a receive antenna using electromagnetic signals. When the system is in an inactive mode, the region is occupied by water. When the system is in an active mode, fluid having a reduced conductivity is introduced into the region to provide transmission of electromagnetic signals with a lower attenuation and thereby facilitate a higher data transfer rate for a given range of communication between the transmit antenna and the receive antenna.

Abstract: A system for monitoring movement in a subsurface environment, which may be used to determine flow dynamics within a fluid mass such as an ore body, or track subsurface persons or moving assets. A plurality of underground positioning system (UPS) elements in the subsurface environment transmit characteristic signals to a plurality of antennas, which transmit the signals to a data processing apparatus. The system thus determines changes in the positions of the UPS elements to derive an indication of the motion of the fluid mass or the locations and movement of subsurface persons or assets.

Abstract: An apparatus for detecting a position of a component in an earth formation is disclosed. The apparatus includes: a transmitter configured to emit a first magnetic field into the earth formation and induce an electric current in the component, the transmitter having a first magnetic dipole extending in a first direction; and a receiver for detecting a second magnetic field generated by the component in response to the first magnetic field, the receiver having a second magnetic dipole extending in a second direction orthogonal to the first direction. A method and computer program product for detecting a position of a component in an earth formation is also disclosed.

Abstract: Apparatus and method for estimating the 3D orientation angles for remotely deployed devices with flexible arms such as dipole antennas of receivers used in marine controlled-source electromagnetic surveys to explore for hydrocarbons. Acoustic transponders or transducers, or other positioning sensors such as attitude sensors or strain-sensitive fiber optic cables are placed on each electrode arm of the receiver. Acoustic sensors (101) on the receiver frame (94) work in conjunction with the positioning sensor(s) (101) on the electrode arms (92) to provide accurate 3D spatial position of the receiver electrodes (93) relative to the receiver frame. Alternatively, sonar transducers mounted on the frame are used to image the electrode arms, which image can be enhanced by fixing reflectors to the arms. An attitude sensor is mounted on the receiver frame, enabling conversion of the relative electrode positions to an earth reference frame.

Abstract: The present invention relates to a sensor arrangement. In particular, a sensor for the measurement of magnetically active or ferrous debris, for example, as generated as a result of machine wear. There is provided a sensor (5) having a magnetic sensor head adapted to produce a magnetic field, —a magnetic field sensor (10) responsive to changes in the magnetic field; a temperature probe (15); and processing means (50) for determining the amount of debris accumulated on the magnetic sensor head based on both magnetic field and temperature data.

Abstract: A method for estimating the effects of an airwave in marine electromagnetic data measured using a source and at least one receiver. The method involves measuring the electromagnetic response at two different under water source-receiver separations and using measurements at the larger separation to estimate the airwave response at that separation. The airwave effect in the response measured at the shorter separation can then be determined using the estimated airwave response at the larger separation.

Abstract: Location determination is performed using a transmitter including an elongated generally planar loop antenna defining an elongation axis. The elongation axis is positioned along at least a portion of a path. A magnetic field is then generated which approximates a dipole field. Certain characteristics of the magnetic field are then determined at a receiving position radially displaced from the antenna elongation axis. Using the determined certain characteristics, at least one orientation parameter is established which characterizes a positional relationship between the receiving position and the antenna on the path. The magnetic field may be transmitted as a monotone single phase signal. The orientation parameter may be a radial offset and/or an angular orientation between the receiving position and the antenna on the path. The antenna of the transmitter may be inserted into a first borehole to transmit the magnetic field to a receiver inserted into a second borehole.

Abstract: An array of electromagnetic receiver antennae is arranged and operated in conjunction with the operation of an array of far field electromagnetic transmitter antennae for mapping subsurface features of an existing well site reservoir. Mapping is performed according to the relative intensities, frequencies, phase shifts, and/or other reflected signal parameters of the reflections received by the receiver antennae (relative to the transmit signals) associated with a given location or target area within a reservoir so as to aid in determining the geological features about an oil deposit for an existing oil well.

Abstract: The present invention relates to a method and apparatus for evaluating and measuring the geometry of a fracture.

Abstract: A method of determining the nature of subterranean strata. The transmitter antenna is towed by vessel at a distance h above the sea floor. The antenna omits a wave field whose strength is proportional to the current delivered to the antenna and this is monitored. The input voltage to the antenna is also measured and changes in antenna impedance are calculated. Changes in antenna impedance are used together with seismic information to determine the nature of the subsea strata.

Abstract: Apparatus and method for a steerable horizontal electric dipole source system for underwater deployment as a moving source in electromagnetic surveying of subsurface regions for hydrocarbons. Position locating sensors (195) are placed near each electrode (26, 27), and means (197, 198) are provided for correcting the electrodes to be at the same elevation with azimuth aligned with the source tow line (11) and the electrode mid-point positioned over the source tow line, based on instantaneous location information from the sensors. The streamer (28) connecting the electrodes may also be monitored for shape by sensors, with corrections made by lateral and vertical control means disclosed herein. The invention can be applied to any marine streamer used in geophysical surveys, including a towed streamer (191) of electromagnetic or seismic receivers (192).

Abstract: There is disclosed a method of performing a controlled source electromagnetic survey, which includes in one embodiment deploying a receiver and an electric dipole source. The source defines a dipole axis. An electromagnetic field is transmitted from the electric dipole source. First and second horizontal components of an electromagnetic field response are detected using the receiver. A vertical component of the electromagnetic field response is then estimated using the detected first and second horizontal components of the electromagnetic field response.

Abstract: A method for providing information about a region below the earth's surface, comprises a) providing data from a system comprising an inductive source providing inductive signals in the region and a plurality of galvanic receivers for receiving galvanic signals resulting from the inductive signals, wherein the galvanic signals are the result of mode conversion occurring in the subsurface region; and b) processing the data. Step b) may include generating at least one galvanic virtual source signal.

Abstract: A method for designing a controlled-source electromagnetic survey that will discriminate between a defined deep marginal-interest reservoir (2) and specified false positive resistivity structures of concern (3, 4, 5). A reservoir model and a false positive model are constructed for each false positive scenario. The resistivity of the false positive model may be tuned to give electromagnetic data similar enough to the reservoir model when forward modeled that any differences fall in the model null space. A null-space discriminating ratio (“NSDR”) is defined, for example as the peak normalized difference of the two related modeled electromagnetic field data sets. An area coverage display of NSDR values (6) allows determination of such additional data as may be needed to distinguish the false positive body, and a survey design is developed accordingly (7). Reduction of the number of variables affecting the area coverage displays is a key feature of the method.

Abstract: A method for determining orientation of an electromagnetic survey sensor includes deploying the sensor at a selected position on the bottom of a body of water. An electromagnetic field is generated at a selected position in the body of water. A portion of the electromagnetic field is detected along at least two orthogonal directions at the sensor. A portion of the detected electromagnetic field is selected as having traveled only in a vertical plane which includes both source position and sensor position. The polarization direction of the selected portion of the electromagnetic field is determined from the selected portion. The determined polarization direction is used to determine the sensor orientation.

Abstract: A method for electromagnetic surveying subsurface formations includes inducing an electromagnetic field in the subsurface formations by passing electric current through a transmitter. Response of the subsurface formations to the induced electromagnetic field is detected at a first plurality of spaced apart positions disposed longitudinally within a bipole length of the transmitter. A direct induction response is removed from the detected response.

Abstract: A system for offshore hydrocarbon electromagnetic prospecting is described. The system includes a transmitter generating electromagnetic energy and injecting an electrical current into a flooded vertical cable. Electromagnetic fields generated by this current in the medium are measured by total field magnetometers or gradiometers. The measured response, which is sensitive to the resistivity of targets, is used to search for and identify hydrocarbon reservoirs. A method for offshore hydrocarbon electromagnetic prospecting is described as well.

Abstract: A method for determining resistivity distribution of formations below a bottom of a body of water from transient electromagnetic signals acquired by imparting a transient electromagnetic field into the water and detecting an electromagnetic response thereto at a plurality of spaced apart positions from a place of the imparting includes simulating an air wave response at each of the plurality of spaced apart positions. The simulated air wave response is subtracted from the detected response to produce a subsurface impulse response at each of the plurality of positions. The subsurface impulse responses are used to determine the resistivity distribution.

Abstract: A method for correcting errors in LWD depths includes performing torque and drag model analysis using drillstring weight, downhole friction, weight on bit, thermal expansion, rig heave and tide to produce a corrected time-depth file, wherein the torque and drag model is automatically calibrated using effective block weight, drillpipe wear, and sliding friction; and correcting time-based LWD data using the corrected time-depth file to produce depth-corrected LWD data. A system for correcting errors in LWD depths includes a processor and a memory that stores a program having instructions for: performing torque and drag model analysis using drillstring weight, downhole friction, weight on bit, thermal expansion, rig heave and tide to produce a corrected time-depth file, wherein the torque and drag model is automatically calibrated using effective block weight, drillpipe wear, and sliding friction; and correcting time-based LWD data using the corrected time-depth file to produce depth-corrected LWD data.

Abstract: A sensor cable for surveying. The sensor cable has a housing, which includes one of more electrodes and a conductive gel surrounding the one or more electrodes. The conductive gel is configured to conduct electrical current to the one or more electrodes and keep the one or more electrodes moist. The housing may also have a membrane surrounding the conductive gel, wherein the membrane is configured to hold the conductive gel in contact with the one or more electrodes and permit electric current to flow between a surrounding medium and the conductive gel.