Abstract: The present application provides a device and method for determining formation resistivity outside casing. The device measures the electrical signal of alternating current flowing along the casing, and then calculates phase velocity, group velocity, time difference, amplitude attenuation, and phase difference of the alternating current along the casing. Using these relationships between phase velocity, group velocity, time differences, amplitude attenuation, and phase difference, the formation resistivity outside the casing is calculated.

Abstract: A depth positioning method to position a production logging tool (1) and a measurement log in a hydrocarbon well (3) in production obtained by means of the tool, the depth positioning method comprises: generating (S1, S2, S3, S1?, S2?, S3?, S11, S12, S13) a set of magnetic measurements (MAG1, MAG) of a depth portion of the hydrocarbon well from a first passive magnetic sensor along the depth portion of the hydrocarbon well, the set of magnetic measurements comprising magnitude and/or direction measurements of the magnetic field that forms a characteristic magnetic field pattern representative of a surrounding magnetic environment of the hydrocarbon well all along the depth portion; comparing (S4, S4?, S14) the set of magnetic measurements (MAG1, MAG) to another set of magnetic measurements (MAG_R, MAG2), the other set of magnetic measurements being a reference set of magnetic measurements generated either by a same or similar passive magnetic sensor deployed and run in the hydrocarbon well earlier, or by a

Abstract: Detecting discontinuities in a well casing according to some aspects includes actively monitoring the electric current response in an antenna or in antennas during the insertion of a tubing string. The method does not require permanent magnets, or any hardware elements beyond those that are already present in a typical behind-casing measurement system. A system according to some aspects includes an antenna that is mounted in or on a tubing string and a voltage source that can be connected to the antenna. A processing device is connected to the antenna and the voltage source. The processing device applies an AC voltage to the antenna and monitors a current generated in the antenna while the AC voltage is being applied.

Abstract: The present invention provides a methodology and system for determining formation resistivity beyond a casing. Using devices to generate, direct, and measure electric signals, the travel speed, travel time, attenuation and phase shift of an electric signal traveling through the casing can be measured. Applying a relationship between the travel speed or travel time of an electric signal and the formation resistivity beyond a casing, it is then possible to determine the formation resistivity beyond a casing by measuring the travel speed or travel time or phase shift or attenuation of an electric signal.

Abstract: Methods, systems, and computer program products for inspecting a pipe in a well using an eddy-current based pipe inspection tool comprises conveying the pipe inspection tool through the well, obtaining a first voltage measurement at an axial position along the pipe from at least one main receiver. The first voltage measurement includes a residual voltage induced in the at least one main receiver by a residual magnetic field resulting from residual magnetism in the pipe. A second voltage measurement is obtained at said axial position along the pipe from at least one second receiver. The first voltage measurement and the second voltage measurement are processed to obtain a processed measurement representing a difference between the first and second voltage measurements. The processed measurement is substantially free of the residual voltage and may be use to estimate a thickness of the pipe and other pipe characteristics.

Abstract: A device can include a housing; external electrodes; circuitry disposed in the housing where the circuitry converts analog signals sensed by the external electrodes to digital signals. Various other apparatuses, systems, methods, etc., are also disclosed.

Abstract: A system for ranging between two wellbores where an emitter electrode and return electrode of a current injection system are disposed to drive a current to a conductive member within a target wellbore to create an electromagnetic field about the conductive member. The electromagnetic field is measured utilizing a sensor disposed in an investigative wellbore, which may be in the process of being drilled. In some embodiments, the emitter electrode and return electrode are positioned on the surface of a formation, spaced apart from one another with locations on the surface selected to optimize current, and therefore, the electromagnetic field, at a desired point along the conductive member. In some embodiments, one or both of the emitter electrode and return electrode are positioned in the target wellbore.

Abstract: A system enables a borehole casing to be used to connection with establishing electromagnetic fields within the earth at the depth of formations of interest over a significant surface area. A particular advantage is that a borehole casing can be used as an essential part of the system, without needing to open the borehole.

Abstract: The disclosure relates to an apparatus and a method for well logging as well as a data processing device thereof. Said apparatus for well logging comprises a drill collar body and an array of antennas, wherein said array of antennas comprises at least a pair of transmitting antenna and receiving antenna, said transmitting antenna and receiving antenna are configured for generating a curve of axial forward depth of investigation. By employing the method for well logging according to the present invention, not only the variation of resistivity in the axial forward formation may be measured in real time during the drilling, but also the interfacial characteristics of the axial forward formations having different resistivity may be discriminated during drilling.

Abstract: A radio frequency (RF) antenna assembly configured to be positioned within a wellbore in a subterranean formation for hydrocarbon resource recovery may include an RF transmission line and an RF antenna coupled to the RF transmission line. The RF antenna assembly may also include an adjustable balun that may include a tubular balun housing surrounding the RF transmission line and defining a space therebetween. The adjustable balun may further include an adjustable shorting body slidably movable within the space and contacting the tubular balun housing and the RF transmission line at an adjustable shorting position.

Abstract: Methods and systems for determining whether a tool has been deployed below a drill pipe are provided. A downhole tool can measure various characteristics, which then can be analyzed to determine the likelihood of a tool having been deployed below the drill pipe. For example, density and porosity measurements can be affected by the presence of casing or drill pipe, and thus such measurements can provide an indication of whether the tool has been deployed below the drill pipe.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, apparatus including: a carrier configured to be conveyed through the borehole; a transducer disposed at the carrier and configured to transmit and/or receive electromagnetic energy into and/or from the earth formation to estimate the property; wherein the transducer includes a plurality of inductively coupled elements in a series, each element configured to transmit and/or receive electromagnetic energy and at least a first connection to a first element in the plurality and a second connection to a second element in the plurality with at least one of the first element and the second element being disposed between end transducer elements in the series.

Abstract: A drilling system includes integral drill bit body and logging while drilling tool body portions. There are no threads between the drill bit and the LWD tool. In one exemplary embodiment the drilling system includes a unitary tool body, i.e., a tool body formed from a single work piece. In another exemplary embodiment the drill bit body portion is welded to the LWD tool body portion. At least one LWD sensor is deployed in the drill bit. The drilling system enables multiple LWD sensors to be deployed in and near the bit (e.g., on both the side and bottom faces of the bit). The absence a threaded connection facilitates the placement of electrical connectors, LWD sensors, and electronic control circuitry at the bit.

Abstract: An apparatus for evaluating the possibility of casing failure in a borehole measures azimuthal changes in a property responsive to azimuthal changes in axial stress. The measurements may be of acoustic velocity, magnetic permeability, and Barkhausen noise.

Abstract: The invention provides a method and apparatus for the analysis of rocks and rock fragments. A method for the analysis of a rock fragment including: feeding the rock fragment to a microwave irradiation zone of microwave energy generated by a microwave source; gauging energy absorbed by the rock fragment; and correlating rate of change of the gauged energy absorbed by the rock fragment with compositional characteristics of the rock fragment.

Abstract: A system for measuring a resistivity parameter of an earth formation includes: at least one measurement electrode electrically connected to a first electrical source; at least one guard electrode; a shielding electrode interposed between the at least one guard electrode and the at least one measurement electrode, the shielding electrode being electrically connected to a second electrical source independent from the first electrical source, and the guard electrode being electrically connected to a third electrical source independent of the first and second electrical sources; at least one return electrode; insulators positioned between (i) the measurement electrode and the shielding electrode, (ii) the shielding electrode and the guard electrode and (iii) the measurement electrode, the guard electrode and the return electrode; and a processor configured to adjust at least one of the first electrical source and the second electrical source to minimize a current flow through the shielding electrode.

Abstract: Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver is deployed into the cased section of the borehole. Electromagnetic survey measurements and impedance measurements relating to impedance of the transmitter and/or receiver are made while deployed in the section of the borehole. Compensation is made for the attenuation amplitude and/or phase in the electromagnetic survey measurements due to the conductive casing. The compensation is based on the impedance measurements and equivalent circuit parameters. The impedance measurements are correlated with numerical modeling results of a purely inductive electromagnetic transducer, and calculated equivalent circuit parameters are combined with the numerical modeling results.

Abstract: The present disclosure relates to determining attenuation factors relating to an electromagnetic signal passing through, a conductive material seen by a real sensor. A sensor is provided and disposed proximate to the material. An alternating current is passed through the sensor and the impedance of the sensor is measured. The impedance of an ideal coil is obtained from the measured impedance using electromagnetic modeling combined with a circuit analysis of the coil impedance, and the attenuation factors for the real coil in straight or feedback mode are determined by electromagnetic modeling of casing attenuation factors and impedance of an ideal coil combined with equivalent circuit modeling of the sensor transfer functions. The attenuation factors seen by the real sensor may be determined in real-time or post-survey. The material may be magnetic or non-magnetic.

Abstract: A current sensor measures an electrical current flowing in well casing or other magnetic structure. The current sensor can be installed in a tool for performing electromagnetic (EM) induction surveying in a wellbore lined with an electrically conductive casing. The tool includes an EM element to transmit or receive a magnetic field through the casing. The measured current using the current sensor can be used to relate the change of casing effect on the EM element (e.g., an induction receiver) placed inside the well casing for performing the EM induction survey.

Abstract: A method and apparatus for evaluating an earth formation penetrated by a borehole comprises taking resistivity measurements using a plurality of resistivity arrays or pads positioned within the borehole proximal the borehole wall. In one embodiment, pads are spaced apart azimuthally around the perimeter of a tool body, each pad carrying at least one electrode thereon. A sequence of resistivity measurement operations are performed involving sequentially operating each pad, in turn, as a transmitter, with remaining pads and electrodes operated as return electrodes. The sequence preferably involves a succession of adjacent pads around the perimeter of the tool body, resulting in a full rotational (360°) imaging of the formation penetrated by the borehole. In one embodiment, the pads include at least two electrodes spaced vertically apart from one another, such that helical current paths are defined between transmitting electrodes and return electrodes.

Abstract: The invention relates to the geophysical examination of wells and can be used for determining the electrical resistivity of rock beds surrounding a well cased in a metal column.

Abstract: The invention relates to a logging tool (1) for determining properties of a fluid (2) surrounding the tool arranged downhole in a casing (3) comprising a wall (4) and having a longitudinal extension. The logging tool has a substantially longitudinal cylindrical shape with a longitudinal axis and, when seen in cross-section, a periphery (5). Moreover, the logging tool comprises a plurality of electrodes (6) arranged spaced around the longitudinal axis in the periphery of the tool so that the fluid flows between the electrodes and the casing wall and a means for measuring the capacitance between two electrodes in all possible combinations giving n*(n?1)/2 capacitance measurements for n electrodes.

Abstract: Earth formations are characterized by using an array of electrodes which can measure streaming potentials in the formation, and by interpreting the data obtained by the electrodes. The electrodes are placed on a wireline tool, a LWD tool, or in a fixed manner about a completed wellbore. The measured streaming potentials are generated by drilling with an overbearing pressure, slitting the mudcake in a borehole, acid injection, or any of various other manners which causes fluid movement. The data obtained is interpreted to locate fractures, measure formation permeability, estimate formation pressure, monitor drilling fluid loss, detect abnormal pressure, etc. Particularly, a streaming potential voltage transient having a double peak profile signifies the presence of a formation fracture.

Abstract: A casing inspection device with magnets and a multi-component flux sensors. The multicomponent sensor enables better definition of the size of defects, particularly in the azimuthal direction.

Abstract: Earth formations are characterized by using an array of electrodes which can measure streaming potentials in the formation, and by interpreting the data obtained by the electrodes. The electrodes are placed on a wireline tool, a LWD tool, or in a fixed manner about a completed wellbore. The measured streaming potentials are generated by drilling with an overbearing pressure, slitting the mudcake in a borehole, acid injection, or any of various other manners which causes fluid movement. The data obtained is interpreted to locate fractures, measure formation permeability, estimate formation pressure, monitor drilling fluid loss, detect abnormal pressure, etc. Particularly, a streaming potential voltage transient having a double peak profile signifies the presence of a formation fracture.

Abstract: An instrument is disclosed for measuring resistivity of Earth formations from within a conductive pipe inside a wellbore drilled through the formations. The instrument includes a plurality of housings connected end to end and adapted to traverse the wellbore. At least one electrode is disposed on each housing. Each electrode is adapted to be placed in electrical contact with the inside of the pipe. The instrument includes a source of electrical current, a digital voltage measuring circuit and a switch. The switch is arranged to connect the source of electrical current between one of the electrodes and a current return at a selectable one of the top of the pipe and a location near the Earth's surface at a selected distance from the top of the pipe, and to connect selected pairs of the electrodes to the digital voltage measuring circuit. The pairs are selected to make voltage measurements corresponding to selected axial distances and selected lateral depths in the Earth formations.

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 system for determining a subsurface parameter from a drilled wellbore includes a casing, a logging tool comprising one or more logging devices, and a latching device coupling the logging tool to the casing such that the logging tool hangs below the casing when the casing is disposed in the wellbore. A method of determining a subsurface parameter includes disposing a casing in a wellbore, coupling the logging tool to the casing such that the logging tool hangs below the casing, and running the casing along the wellbore, wherein the logging tool makes measurements as the casing is run along the wellbore.

Abstract: Apparatus for monitoring an underground formation through which a borehole passes, comprises a conductive casing (6) located in the borehole (1) passing through the formation (4); a plurality of sensors (12-1) for measuring an electrical property of the formation (4) located in the borehole (1) outside the casing (6) and electrically insulated therefrom; and an electrical current source (11) positioned in the borehole (1) passing through the formation (4) and arranged to inject a current into the formation (4); the casing (6) having an electrically insulating coating (14) over the surface thereof, at least in the region of the sensors (12-1), and an electrically conductive portion (11) in electrical contact with the formation (4); and a current supply (10) being connected to the casing (6) such that current flows into the formation (4) from the electrically conductive portion (11) which acts as the current source, the sensors (12-1) measuring the electrical property of the formation (4) resulting from such cu

Abstract: A method is disclosed for locating a receiver in a borehole having a conductive liner by inducing an electromagnetic field from a transmitter in a first borehole, detecting at a first location by at least one receiver located in a second borehole having a conductive liner, a first electromagnetic field induced by the transmitter, detecting at a second location by the at least one receiver, a second electromagnetic field induced by the transmitter and calculating a set of geometry coordinates for the first location based on the first electromagnetic field and the second electromagnetic field.

Abstract: A centralizer (1) for position a casing (3) in a conduit (4) passing through underground formations includes measurement means (7) such as an electrode for deriving at least one representative parameter of the formations.

Abstract: Process for determining the resistivity (Rt) of a formation (9) surrounding a well (10) equipped with a casing (11) consisting of several casing segments (11.i, 11.

Abstract: A method and apparatus for minimizing direct coupling between transmitters and receivers on a downhole logging tool are disclosed. One embodiment includes a transmitter, a bucking device, and a plurality of receivers, where signals may be directly coupled from the transmitter into the receivers and signals may be indirectly coupled from the transmitter into the receivers through the formation and borehole environment. The bucking device minimizes the magnitude of the signals that are directly coupled from the transmitter into multiple receivers within the plurality. By varying the current in the bucking device, the bucking device minimizes the magnitude of the directly coupled signal of each receiver in the plurality, and each receiver may utilize a common bucking device.

Abstract: A system and methods for indicating formation resistivity anisotropy and evaluating the vertical resistivity component by combining array induction measurements and array laterolog measurements. Formation measurements are obtained with an induction tool and a laterolog tool. Formation parameter data are derived from the induction tool measurements. The laterolog tool response is modeled using the derived formation parameter data. The formation resistivity anisotropy and/or the vertical resistivity component are determined from a comparison of the modeled laterolog tool response against the apparent measurements obtained with the laterolog tool.

Abstract: Geological formation resistivity is determined. Circuitry is located within the borehole casing that is adjacent to the geological formation. The circuitry can measure one or more voltages across two or more voltage measurement electrodes associated with the borehole casing. The measured voltages are used by a processor to determine the resistivity of the geological formation. A common mode signal can also be reduced using the circuitry.

Abstract: Apparatus for measuring the resistivity of a formation surrounding a borehole having a conductive casing comprises a tool body; first and second current injectors spaced apart on the tool body for injecting current into the casing; and an insulating body portion disposed between the current injectors, at least three ring electrodes being mounted on the insulating body portion between the current injectors.

Abstract: The invention relates to a device for measuring an electrical parameter through electrically-conductive casing, said device including a current injection electrode (3) and a measurement electrode (7) on one side of the wall of the casing (1). According to the invention, the injection electrode (3) is associated via a first magnetic coupler (4) with a current source (2) and the measurement electrode (7) is associated via a second magnetic coupler (6) with a measurement device (5) situated on the other side of the wall.

Abstract: Apparatus for monitoring an underground formation through which a borehole passes, comprises a conductive casing (6) located in the borehole (1) passing through the formation (4); a plurality of sensors (12-1) for measuring an electrical property of the formation (4) located in the borehole (1) outside the casing (6) and electrically insulated therefrom; and an electrical current source (11) positioned in the borehole (1) passing through the formation (4) and arranged to inject a current into the formation (4); the casing (6) having an electrically insulating coating (14) over the surface thereof, at least in the region of the sensors (12-1), and an electrically conductive portion (11) in electrical contact with the formation (4); and a current supply (10) being connected to the casing (6) such that current flows into the formation (4) from the electrically conductive portion (11) which acts as the current source, the sensors (12-1) measuring the electrical property of the formation (4) resulting from such cu

Abstract: A centralizer (1) for position a casing (3) in a conduit (4) passing through underground formations includes measurement means (7) such as an electrode for deriving at least one representative parameter of the formations.

Abstract: The present invention is a system and method capable of providing continuous measurements of resistivity-through-casing (RTC) of a geological formation traversed by a boreholeby eliminating measurement of the casing resistance. To this end, a real-time feedback control substantially eliminates current flow along the casing in the vicinity of an injection point for injecting a measuring current into the formation. This allows direct estimation of the measuring current injected into the formation along with the casing voltage used to drive the current into the formation. As a result, there is no need for “nulling” or calibration cycle that requires two step measurements with the RTC tool held stationary. The preferred feedback is by the proportional integral derivative procedure (PID) with a digital signal processor that controls bi-directional steerable current sources supplying one or more current to the casing at various points.

Abstract: The invention relates to a method and apparatus for studying the resistivity of a geological formation around a borehole fitted with metal casing. An electric current is applied to the casing so as to cause current to leak into said formation at a given level, and said current is shunted by a feedback circuit in contact with the casing on either side of the measurement level, said circuit being organized to ensure that the current flowing along the casing at said level is less compared with the shunt current, the difference between the voltage drops on the adjacent sections of casing situated on either side of the measurement level is determined, and the leakage current (Ifor) is deduced therefrom.

Abstract: A petroleum well (20) for producing petroleum products that incorporates a system adapted to controllably measure a formation resistivity using induction chokes (91-95) to form electrically isolated piping structure sections that can be used as the formation contact electrodes for time-varying current, and methods of producing petroleum products while measuring formation resistivity, are provided by the present invention. The system comprises a first induction choke (91), a second induction choke (92), and a device (50). The first induction choke (91) is located about a piping structure (30) of the well (20). The second induction choke (92) is also located about the piping structure (30) of the well (20), but the first induction choke (91) is distally spaced from the second induction choke (92). The device (50) is located outside of the piping structure (30) and comprises two terminals (71, 72).

Abstract: A method of determining resistivity of an earth formation through a conductive wellbore casing. The resistance of conductors within an armored electrical cable for a wellbore sonde is measured and the sonde is inserted into the wellbore. The sonde has a plurality of electrodes at axially spaced apart locations for electrically contacting the casing. A first electrical current is applied between a first electrode and a surface return electrode and a first current amplitude and phase is measured. A second phase shifted electrical current is applied between a second electrode and the surface return electrode and the second current amplitude and phase is measured. A first voltage amplitude and phase between a first pair of electrodes axially disposed between the first and second electrodes is measured, and a second voltage amplitude and phase between a second pair of electrodes axially disposed between the first and second electrodes is measured.

Abstract: A method and apparatus for measuring changes in the media within a geologic formation by transmitting magnetic flux through a section of ferromagnetic well casing and measuring the change in flux received back through the casing. The flux transmitter and receiving components may be permanently installed in a hydrocarbon production well.

Abstract: The present invention is a system and method capable of providing continuous measurements of resistivity-through-casing (RTC) of a geological formation traversed by a boreholeby eliminating measurement of the casing resistance. To this end, a real-time feedback control substantially eliminates current flow along the casing in the vicinity of an injection point for injecting a measuring current into the formation. This allows direct estimation of the measuring current injected into the formation along with the casing voltage used to drive the current into the formation. As a result, there is no need for “nulling” or calibration cycle that requires two step measurements with the RTC tool held stationary. The preferred feedback is by the proportional integral derivative procedure (PID) with a digital signal processor that controls bi-directional steerable current sources supplying one or more current to the casing at various points.

Abstract: The invention relates to a method of surveying a geological formation through which a cased borehole passes, said method being characterized by the fact that: in a first step, current is injected into the casing (11) at a first point (In1) spaced apart longitudinally from said formation so as to cause current to leak into said formation, and electrodes (a, b, c) defining two consecutive sections of casing situated at the level of said formation ,ire used to measure the respective potential drops along said sections; in a second step, current is injected into the casing at a second point (In2) spaced apart longitudinally from the formation and situated on the opposite side thereof from said first point, so as to cause current to leak into the formation, and said electrodes are used to measure the potential drops along said sections; the corresponding measurements of the two steps are combined to obtain the values corresponding to a circuit formed by the casing between the two injection points is and essenti

Abstract: A system for measuring magnetic fields outside a ferromagnetic container from inside the same container is described. The invention uses magneti circuits to direct the flow of magnetic flux to a magnetic field detector. By using magnetic fields for detection, this invention is able to measure the properties of magnetic materials outside the ferromagnetic container, such as a geologic formation, electric or magnetic parameters, or log well and drill holes that have been cased.

Abstract: A bicycle computer includes a base member structured to mount to a structural member of a bicycle. A cover having an inner surface is swingably coupled to the base so that the inner surface may be moved from a closed position where the inner surface faces the base member to an open position where the inner surface may be viewed or accessed by a user.

Abstract: An apparatus for borehole electric-field telemetry that comprises a source of modulated voltage or current, at least one axially non-conductive collar connected between pipe sections in a pipe string, and a system of insulated wireline components providing electrical connections, insulated from drilling fluids, between the ends of the one or more aforementioned insulated collars in the pipe string, to transmit the voltage to current.

Abstract: Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information useful to determine the resistivity of adjacent geological formations from within the cased well are described. The multiple electrode apparatus has a plurality of spaced apart voltage measurement electrodes that electrically engage a portion of the interior of the cased well. During measurements of information useful to determine formation resistivity, current is conducted between a first current conducting electrode in electrical contact with the interior of the cased well to a second current conducting electrode that is also in electrical contact with the interior of the cased well. The first and second current conducting electrodes are separated by a distance sufficient so that at least a portion of the current conducted between the first and second current conducting electrodes is conducted through the geological formation of interest.