Abstract: Multimodal geosteering systems and methods are disclosed. Some disclosed tool embodiments include first and second transmitter-receiver arrangements that make geosteering measurements using different forms of energy (such as acoustic and electromagnetic energy) to provide geosteering measurements that at least indicate a boundary direction but may also indicate a boundary distance. Some disclosed method embodiments include: determining a direction to a bed boundary using measurements with different energy types; and adjusting a drilling direction based at least in part on said determination. Combinations of (or selections between) the different measurements may be made based on, inter alia, measurement range, resolution, and contrast. Some disclosed system embodiments include a memory and a processor. The memory stores geosteering display software that configures the processor to generate an image with different regions based on the different types of geosteering measurements.

Abstract: A logging tool for use in a wellbore having a sensor portion for making measurements. The tool has a sleeve enclosing the sensor portion and made of a material that is transparent to the measurements being made. One or more structural elements having physical characteristics different from the material comprising the sleeve are carried on the sleeve to enhance the mechanical properties of the sleeve.

Abstract: A method for measuring a resistivity parameter of an earth formation is provided. The method includes: conveying a measurement current from at least one measurement electrode into the formation, the at least one measurement electrode having a potential; receiving the measurement current by at least one return electrode; and estimating a resistivity parameter from a measurement value selected from at least one of the measurement current and the potential, the resistivity parameter based on (i) an impedance calculated from the measurement value and (ii) a correction factor calculated from a plurality of measurement values related to a conductivity of a fluid in a borehole and a dielectric constant of the fluid in the borehole. A system for measuring a resistivity parameter of an earth formation is also provided.

Abstract: Oil-based mud imaging systems and methods that measure formation permittivity. In some embodiments, disclosed logging systems include a logging tool in communication with surface computing facilities. The logging tool is provided with a sensor array having at least two voltage electrodes positioned between at least two current electrodes that create an electric field in a borehole wall, and is further provided with electronics coupled to the voltage electrodes to determine a differential voltage magnitude and phase. From the magnitude and phase, formation resistivity and permittivity measurements can be determined and used to construct a borehole wall image.

Abstract: A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated with the module. The electrodes are arranged to measure electric field in a direction along the direction of the cable. The cable is arranged to form a closed pattern. Another marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Abstract: A method and system for measuring formation resisitivity is achieved by introducing one or more continuous phase modulated electrical signals into the formation, each signal introduced at a different location. The current of each introduced electrical signal is then sensed, producing an analog voltage signal as a measurement of the formation. Each introduced electrical signal is compared with its respective measured signal of the formation. Each comparison is made in a quadrature demodulation device, producing an in-phase demodulated signal. A quasi-direct-current signal is extracted from each in-phase demodulated signal, producing an analog measurement related to the resistivity of the formation. Each analog measurement is converted into a digital value for further processing. Successive measurements are digitally summed and averaged to increase the signal to noise ratio.

Abstract: A method of accurately measuring earth resistance even when the composition state of soil that affects the installation of a metering device for measuring earth resistance is unknown. The method comprises measuring a potential at a first potential electrode point, measuring a potential at a second potential electrode point, calculating a voltage slope corresponding to a change rate of potential difference, using a potential difference between the first and second potential electrode points, and setting a potential point according to voltage slope characteristics and measuring earth resistance. A measurement approximating an accurate value of earth resistance can be performed even when soil composition characteristics are unknown at a site.

Abstract: A receiver streamer system for marine electromagnetic surveying includes a first streamer, and a second streamer disposed substantially parallel to and spaced apart from the first streamer. A first pair of electrodes is associated with the first streamer and a second pair of electrodes is associated with the second streamer. Each of the first and second pairs of electrodes is functionally associated with a voltage measuring circuit configured to measure voltage along an inline direction. At least one electrode on each of the first and second streamers is configured and associated with a voltage measuring circuit to make voltage measurements in a cross-line direction.

Abstract: Method for removing air wave noise from shallow water controlled source electromagnetic survey data, using only the measured data and conductivity values for sea water (140) and air. The method is a calculation performed numerically on CSEM data and resulting in an estimate of those data that would have been acquired had the water layer extended infinitely upward from the seafloor. No properties of the sub-sea sediments are used. Synthetic electromagnetic field data are generated for (a) an all water model (141) and (b) an air-water model (146-147) of the survey region. These simulated results are then used to calculate (148-150) electromagnetic field values corresponding to a water-sediment model with water replacing the air half space, which represent measured data adjusted to remove air wave noise.

Abstract: The average current at a plurality of measure electrodes of a resistivity imaging tool is determined and subtracted from the individual measure currents to give a resistivity image with improved dynamic range.

Abstract: A communications system including: a plurality of sub-surface portable transceivers each including: a digital data source, a modulator coupled to the digital data source, a power amplifier coupled to the modulator and a loop antenna inductively coupled to the power amplifier; and a base transceiver including: an electrically insulated ferrite core antenna for receiving magnetic signals, an electric di-pole antenna for receiving ambient noise, a noise canceller coupled to the insulated ferrite core antenna and electric dipole antenna and responsive to the electric-dipole antenna to filter noise from signals received via the insulated ferrite core antenna, a demodulator coupled to the noise canceller and a decoder coupled to the demodulator.

Abstract: A method for correcting a measurement of a property of a subsurface material includes: selecting an instrument that includes a test circuit and a separate sensor, the sensor adapted for transmitting an electric signal into the subsurface material and receiving a data signal from the subsurface material, wherein the test circuit and the sensor are switchably coupled to an electronics unit of the instrument; receiving the electric signal from the test circuit in the electronics unit; using the electronics unit, measuring at least one output characteristic of the instrument; and applying a correction to the data signal according to the measured output characteristic. An instrument and an additional method are provided.

Abstract: A well logging instruments includes an electrically conductive sonde mandrel. At least one electrical sensor is affixed to an exterior of the mandrel. The sensor is configured to be attached to the mandrel by sliding along an exterior surface thereof. A pressure-sealing electrical feedthrough bulkhead makes electrical connection from the at least one sensor through a wall of the mandrel.

Abstract: Sensor assemblies including transmitter and receiver antennas to respectively transmit or receive electromagnetic energy. The sensor assemblies are disposed in downhole tools adapted for subsurface disposal. The receiver is disposed at a distance less than six inches (15 cm) from the transmitter on the sensor body. The sensor transmitter or receiver includes an antenna with its axis tilted with respect to the axis of the downhole tool. A sensor includes a tri-axial system of antennas. Another sensor includes a cross-dipole antenna system.

Abstract: A detector for a marine electromagnetic survey system includes a housing arranged to minimize turbulence when the housing is towed through a body of water, and to minimize motion of the housing in any direction other than the tow direction. The housing includes at least one of an electric field and a magnetic field sensing element associated therewith.

Abstract: Disclosed herein is a method of measuring a resistivity parameter of an earth formation. The method includes: applying a first electric measurement current including a first series of pulses to a first electrode and inducing a first formation current in the earth formation; applying a second electric measurement current including a second series of pulses to a second electrode and inducing a second formation current in the earth formation, the first series of pulses and the second series of pulses occupying distinct portions of a time domain in a selected time window; measuring the first measurement current, the first formation current, the second measurement current and the second formation current by coherent in-phase demodulation; and calculating at least one resistivity parameter by i) comparing the first measurement current to the first formation current and ii) comparing the second measurement current to the second formation current.

Abstract: Techniques for surface exploration and monitoring are presented. In representative embodiments, a system is provided that can 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 and 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: Methods and devices are provided for investigating an earth formation use electro-kinetics and/or electro-osmosis measurements. In one example, the method includes creating a pressure difference in the earth formation proximate to a wellbore; measuring a generated electro-kinetic property of the earth formation proximate to the wellbore, the generated electro-kinetic property generated by the pressure difference; applying an electric field to the earth formation proximate to the wellbore; measuring a generated pressure change in the earth formation proximate to the wellbore, the generated pressure change generated by the electric field; and determining wettability of the earth formation proximate to the wellbore by the use of the measurement of the generated electro-kinetic property and the measurement of the generated pressure change.

Abstract: A composite encased tool for making subsurface measurements in a borehole traversing a subsurface formation includes a conductive mandrel, a first composite layer wrapped around the conductive mandrel, the first composite layer having one or more slots, a source or sensor disposed in each of the one or more slots, and a second composite layer wrapped around the first composite layer with the source or sensor in the one or more slots.

Abstract: Using an electromagnetic logging tool, desired antenna responses are synthesized from a combination of measured antenna responses, as well as antenna arrays particularly suited to provide the measurements. Those arrays may include cross dipole and double cross dipole antennas. Direct and derivative responses are used to synthesize the desired response, and the synthesized desired response is used to determine formation properties.

Abstract: A method and apparatus for measuring the through-thickness resistance or conductance of a thin electrolyte is provided. The method and apparatus includes positioning a first source electrode on a first side of an electrolyte to be tested, positioning a second source electrode on a second side of the electrolyte, positioning a first sense electrode on the second side of the electrolyte, and positioning a second sense electrode on the first side of the electrolyte. current is then passed between the first and second source electrodes and the voltage between the first and second sense electrodes is measured.

Abstract: A connector for a downhole tool includes a body with one or more conductors positioned at least partially axially adjacent to an axial bore that extends at least partially through the body. In embodiments, one or more seals surrounding the body prevent fluid from flowing from a lateral opening into the interior of the downhole tool. Additionally, the body of the connector can include a circumferential or annular recess that acts as a reservoir to contain or capture fluid that might otherwise enter the sub. Leak protection can also be protected by applying a pressure compensating material around the body.

Abstract: Dynamic gain setting is provided for a multiphase flow measuring device that measures in-phase and quadrature signals. The average current at a plurality of measure electrodes is determined and subtracted from the individual measure currents to give a measurement with improved dynamic range.

Abstract: A receiver for electromagnetic measurements includes a polyhedron structure having m faces, where m?4 and m?6: n electrodes each disposed on one face of the polyhedron structure, wherein 3?n?m; and at least one circuitry connected to the n electrodes for signal measurement. A method for electromagnetic measurements includes obtaining a plurality of electric current measurements using a plurality of electrodes each disposed on a surface of a polyhedron receiver, wherein the plurality of electric current measurements comprise at least three different measurements; and determining electric field components in a three dimensional space from the plurality of electric current measurements by using a number of matrices that correlate orientations of surfaces of the polyhedron receiver to a coordinate system in the three dimensional space.

Abstract: An apparatus, method and computer-readable medium for estimating a resistivity property of an earth formation in a borehole filled with oil-based mud. The method includes conveying a logging tool into a borehole; measuring a plurality of impedance values of the earth formation, each of the plurality of impedance values being obtained at one of a plurality of measure electrodes on the logging tool; determining a coefficient related to an electrical property of the mud from a plurality of pairs of impedance values; estimating the resistivity property of the formation from the determined coefficient; and recording the resistivity property on a suitable medium.

Abstract: A method for non-invasive mapping (imaging) of the electrical impedance of an object. The present invention provides a method, current density impedance imaging (CDII) which produces an impedance image of object by measuring current density distributions and directly calculating the local impedance values.

Abstract: A marine electromagnetic survey cable includes a reference electrode extending substantially along the entire length of the cable. A plurality of spaced apart measuring electrodes is disposed along the cable and each is electrically insulated from the reference electrode. A voltage measuring is circuit functionally coupled between each measuring electrode and the reference electrode.

Abstract: A bottom system related to equipment deployed for seabed geo-electrical survey is proposed, in preferred embodiments comprising a basic module, including registration and power supply means, or a combination of the basic module with at least one additional module: a magnetic characteristics measuring module or/and a seismic characteristics measuring module. The additional modules are connected with other modules through hermetic connectors. The modules are attached to a load with Kevlar straps, provided with an electrochemical release system. Arms with electrodes measuring electromagnetic characteristics of seabed, are attached to the basic module, in their initial position directed upwards at minimum 15° from the vertical, and fixed with fixing elements, connected with a releasing element of a device for descending and lifting the bottom station. The arms are made telescopic for convenient transportation.

Abstract: Logging-while-drilling apparatus and methodologies for measuring streaming potential in an earth formation are provided. The apparatus and methodologies can be utilized to find information relevant to the drilling operations. In particular, since the streaming potential measurement relates directly to fluid flow, the streaming potential measurements can be used to track flow of fluids in the formation. In turn, this information may be used to find information relevant to the drilling operations, such as under-balanced drilling conditions, abnormal formation pressures, open fractures, the permeability of the formation, and formation pressure.

Abstract: An apparatus for making azimuthally sensitive resistivity measurements of a subterranean formation is disclosed. The apparatus includes a magnetically permeably ring deployed about an electrically conductive tool body. An AC voltage supply is coupled to the tool body on opposing sides of the magnetically permeable ring, with at least one connecting conductor crossing outside the ring. Exemplary embodiments of this invention may further include one or more current sensing electrodes deployed in and electrically isolated from an outer surface of a blade deployed on the tool body and may be utilized to make azimuthally resolved formation resistivity measurements.

Abstract: A receiver streamer system for marine electromagnetic surveying includes a first streamer, and a second streamer disposed substantially parallel to and spaced apart from the first streamer. A first pair of electrodes is associated with the first streamer and a second pair of electrodes is associated with the second streamer. Each of the first and second pairs of electrodes is functionally associated with a voltage measuring circuit configured to measure voltage along an inline direction. At least one electrode on each of the first and second streamers is configured and associated with a voltage measuring circuit to make voltage measurements in a cross-line direction.

Abstract: Method for conducting an efficient and interpretable controlled-source electromagnetic reconnaissance survey for buried hydrocarbons. While a part of the survey area is being set up for measurement and data are being acquired, data from a nearby part of the survey area, surveyed just previously, are being rapidly processed and analyzed (110). If the analysis shows resistive anomalies of interest in a portion of a survey area, a fine-grid survey is quickly designed for that portion, and that survey is conducted next before moving source and receivers to a more distant part of the survey area.

Abstract: A sensor for electric field measurement at the floor of a body of water has at least one pair of square or rectangular electrodes (139, 140) with a known area positioned in parallel separated by a distance and connected by a resistor (120) having a value that matches the resistance of the water between the electrodes. The detected electric fields may be naturally-occurring or artificially generated using a controlled electromagnetic (EM) source. In a preferred embodiment, three pairs of square or rectangular parallel electrodes (139-144) are arranged to form the six sides of a rectangular prism or cube, thus providing for electric field measurement along three axes to provide horizontal and vertical measurements of a hydrocarbon reservoir or other feature of interest under the floor of the body of water.

Abstract: A marine electromagnetic survey cable includes a reference electrode extending substantially along the entire length of the cable. A plurality of spaced apart measuring electrodes is disposed along the cable and each is electrically insulated from the reference electrode. A voltage measuring is circuit functionally coupled between each measuring electrode and the reference electrode.

Abstract: Logging-while-drilling apparatus and methodologies for measuring streaming potential in an earth formation are provided. The apparatus and methodologies can be utilized to find information relevant to the drilling operations. In particular, since the streaming potential measurement relates directly to fluid flow, the streaming potential measurements can be used to track flow of fluids in the formation. In turn, this information may be used to find information relevant to the drilling operations, such as under-balanced drilling conditions, abnormal formation pressures, open fractures, the permeability of the formation, and formation pressure.

Abstract: A resistivity imaging apparatus includes: a first sensor electrode disposed on an electrode pad and positioned at a first standoff; a second sensor electrode disposed on the electrode pad and adjacent the first sensor electrode, the second sensor electrode positioned at a second standoff; and a return electrode disposed on the electrode pad, wherein the sensor electrodes and the return electrode are configured for injecting current into a formation and receiving a signal from the formation. Other embodiments, methods and computer program products are disclosed.

Abstract: A constant contact reference wheel system includes a vehicle carrying a water reservoir, and a constant contact reference wheel. The constant contact reference wheel includes a frame having a first end and a second end, an attachment mechanism carried by the first end removably coupling the frame to the vehicle, a wheel structure having a rim for rolling contact with a soil surface, and a reference cell carried by the frame. A water pathway extends from the water source to the rim. The rim exudes water for contact with the soil surface, and the reference cell is in fluid communication with the water pathway.

Abstract: A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated with the module. The electrodes are arranged to measure electric field in a direction along the direction of the cable. The cable is arranged to form a closed pattern. Another marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Abstract: An apparatus for making azimuthally sensitive resistivity measurements of a subterranean formation is disclosed. The apparatus includes a magnetically permeably ring deployed about an electrically conductive tool body. An AC voltage supply is coupled to the tool body on opposing sides of the magnetically permeable ring, with at least one connecting conductor crossing outside the ring. Exemplary embodiments of this invention may further include one or more current sensing electrodes deployed in and electrically isolated from an outer surface of the tool body and may be utilized to make azimuthally resolved formation resistivity measurements.

Abstract: A well logging instruments includes an electrically conductive sonde mandrel. At least one electrical sensor is affixed to an exterior of the mandrel. The sensor is configured to be attached to the mandrel by sliding along an exterior surface thereof. A pressure-sealing electrical feedthrough bulkhead makes electrical connection from the at least one sensor through a wall of the mandrel.

Abstract: A method for determining a formation electrical property under a sea floor includes obtaining measurement data using a receiver having an impedance lower than an impedance of seawater at a measurement site; correcting the measurement data to obtain corrected data corresponding to data that would have been acquired using a receiver having an impedance matched with the impedance of the seawater; and deriving the formation property from the corrected data.

Abstract: A method for determining structure in the Earth's subsurface includes generating an initial model of the structure. The initial model includes at least one layer boundary. A wellbore is drilled along a selected trajectory through the Earth's subsurface in a volume represented by the initial model. At least one formation parameter is measured azimuthally along the wellbore. A distance is determined from the wellbore at selected positions therealong to the at least one layer boundary using the azimuthal formation parameter measurements. The initial model is adjusted using the determined distances. In one example, the parameter is resistivity. In one example, the parameter is acoustic velocity.

Abstract: Phase-sensitive measurements are made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation at a plurality of frequencies. From the phase sensitive measurements, the formation resistivity can be determined with higher sensitivity than is possible with the single frequency measurements. Tool standoff can also be determined from a knowledge of the mud resistivity and/or dielectric constant. Formation resistivity may also be determined when the effect of formation capacitance cannot be ignored.

Abstract: Impedance measurements made by a galvanic resistivity tool in a borehole in an earth formation are corrected by a factor that depends on the mud conductivity and the mud dielectric constant. Standoff measurements are not necessary.

Abstract: Logging-while-drilling apparatus and methodologies for measuring streaming potential in an earth formation are provided. The apparatus and methodologies can be utilized to find information relevant to the drilling operations. In particular, since the streaming potential measurement relates directly to fluid flow, the streaming potential measurements can be used to track flow of fluids in the formation. In turn, this information may be used to find information relevant to the drilling operations, such as under-balanced drilling conditions, abnormal formation pressures, open fractures, the permeability of the formation, and formation pressure.

Abstract: A in situ probe for the measurement of the geoelectrical properties of a geological formation. The probe serves as the interface between a standard acquisition system and the earth. The probe is customizable in its length and the type of electrodes used to make contact with the geologic formation. The probe is permanently installed for long term measurements, it contains closely spaced electrodes enabling a high vertical or depth resolution of measurements. The electrode type is customizable either stainless steel or non-polarizing.

Abstract: Measurements made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation are corrected using the tool standoff. The correction involves removing a calibration signal determined in a medium of high conductivity from the measured impedance. The magnitude and/or the real part of the impedance may be used.

Abstract: A sensor for electric field measurement at the floor of a body of water has at least one pair of square or rectangular electrodes (139, 140) with a known area positioned in parallel separated by a distance and connected by a resistor (120) having a value that matches the resistance of the water between the electrodes. The detected electric fields may be naturally-occurring or artificially generated using a controlled electromagnetic (EM) source.

Abstract: A probe 1 for measuring the electromagnetic properties of a down-hole material MC, GF, DM of a well-bore WB comprises a metallic pad 2 in contact with the down-hole material. The pad 2 further comprises an open-ended coaxial wire 4 coupled to an electronic circuit 3. The open-ended coaxial wire 4 comprises an inner conductor 4A sunk in an insulator 4B and is positioned sensibly perpendicularly to the well-bore wall. The electronic circuit 3 is able to send a high-frequency input signal into the open-ended coaxial wire 4 and to determine a reflection coefficient based on a high-frequency output signal reflected by the open-ended coaxial wire 4.

Abstract: A logging tool for use in a wellbore having a sensor portion for making measurements. The tool has a sleeve enclosing the sensor portion and made of a material that is transparent to the measurements being made. One or more structural elements having physical characteristics different from the material comprising the sleeve are carried on the sleeve to enhance the mechanical properties of the sleeve.