Abstract: Transient measurements made at two spaced apart receivers responsive to separate activation of two transmitters symmetrically disposed about the two receivers. The transmitters and receivers are on an instrument having a conductive body induces currents in the earth formation. The effect of the conductive body is removed by using deconvolving the signal at one receiver using the measured signal at the other receiver. The symmetric transmitter configuration also enables compensation for receiver differences.

Abstract: A steerable or non-steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: A method for making directional resistivity measurements includes sequentially transmitting first and second axial and transverse electromagnetic waves in a borehole and receiving substantially pure axial and transverse components of each of the transmitted waves. A composite ratio of the received components is computed and may be utilized as an indicator of various formation parameters. The invention advantageously provides for the acquisition of compensated directional resistivity measurements.

Abstract: An apparatus and method is disclosed for measuring a parameter of an earth formation surrounding a wellbore. A Nuclear Magnetic Resonance (NMR) tool and at least one second tool are conveyed in the wellbore on a wireline, the NMR tool having a magnetic influence on a region of the wellbore. The magnetic influence of the NMR tool is removed from the region of the wellbore using a demagnetizing device. The parameter of the earth formation is measured using the at least one second tool. A second demagnetizing device may be used to remove the magnetic influence of the at least one second tool from the region of the wellbore.

Abstract: A technique for drilling a borehole includes obtaining data from a tool in the borehole for a plurality of positions in the borehole that is being drilled to form acquired data indicative of directional electromagnetic propagation measurements. The technique includes identifying a plurality of distances to a boundary between formations in ground from the plurality of positions in the borehole based on the measurements; identifying a trajectory of the borehole using the plurality of distances; and deciding whether to change the trajectory of the borehole using a change in the plurality of distances between the trajectory and the boundary. The trajectory of the borehole may be changed in both inclination and azimuth.

Abstract: This invention relates to well logging instrumentation, specifically, to measuring devices which use an advanced slip-free borehole contact interaction mechanism. A measuring probe for an oil and gas wells and/or casings includes a main body and at least one robotic arm, fixed to the main body and provided with a polygonal rotating contact tip at the arm's free end. The measuring probe is used as a measuring device and provides a successive slip-free continuous contact between the rotating surface of the tip and the inner wall of the oil & gas wells and/or casings. The tip is furnished with at least one sensor that picks up the geological formations response to a signal emitted directly to the geological formation via the points of contact.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: A steerable or non-steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resistivity in a particular azimuthal direction.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna.

Abstract: A transmitter system for inducing a transient electromagnetic field in an earth formation comprises an inductive element to generate an electromagnetic field in response to a flow of electric current through the inductive element. Furthermore, switching means arranged to interrupt the flow of electric current through the inductive element, which switching means comprises a primary switch and an auxiliary switch arranged in series connection with each other. The auxiliary switch has a lower breakdown voltage than the primary switch. This induces a transient electromagnetic field in the earth formation. Delay circuitry may impose a time delay between switching of the auxiliary switch relative to switching of the primary switch. A transient electromagnetic response signal may be recorded, and used in a method of producing a mineral hydrocarbon fluid.

Abstract: The present invention relates to making one or more measurements in a virgin formation using a downhole tool that includes a miniature logging tool. The downhole tool is disposed in a wellbore penetrating the formation, adjacent to the formation, and a sidetrack borehole is made into the formation. All or a portion of the miniature logging tool is deployed into the sidetrack borehole and measurements are made in the virgin formation using the miniature logging tool. The downhole tool may include a drilling/coring module, a pump module, and packers. The drilling/coring module is used to make the sidetrack borehole, and the packers and pump module can be used to create an underbalanced drilling condition in an isolated section of the wellbore.

Abstract: A shear wave is generated at a borehole wall. A static magnetic field is applied with a radial direction and an oscillating magnetic field is applied tangential to the borehole wall. The frequency of the oscillating field is varied until a resonance condition occurs. Motion of the formation under resonance provides an indication of a resistivity property of the earth formation.

Abstract: NMR spin echo signals are measured in a small borehole during drilling. Signals measured in a plurality of regions of investigation are combined to increase the signal strength.

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: Evaluating a formation by lowering a downhole tool in a wellbore penetrating the formation, injecting a fluid into the formation at an injection zone via the downhole tool, and using a formation evaluation sensor to perform a measurement at each of a plurality of locations in the wellbore each proximate the injection zone. At least two of the plurality of measurements are compared, and a formation property is determined based on the comparison.

Abstract: A method for magnetizing a wellbore tubular is disclosed. The method includes magnetizing a wellbore tubular at three or more discrete locations on the tubular. In exemplary embodiments the magnetized wellbore tubular includes at least one pair of opposing magnetic poles located between longitudinally opposed ends of the tubular. Wellbore tubulars magnetized in accordance with this invention may be coupled to one another to provide a magnetic profile about a section of a casing string. Passive ranging measurements of the magnetic field about the casing string may be utilized to survey and guide drilling of a twin well. Such an approach advantageously obviates the need for simultaneous access to both wells.

Abstract: A method for drilling substantially parallel twin wells includes drilling a first well and deploying a casing string in the first well. A magnetized section of the casing string includes a plurality of magnetized wellbore tubulars having at least one pair of opposing magnetic poles located between longitudinally opposed ends of the wellbore tubular. A portion of a second well is drilled within sensory range of magnetic flux from the magnetized section of the casing string. The local magnetic field is measured in the second well and processed to determine a direction for subsequent drilling. Drilling proceeds along the direction for subsequent drilling.

Abstract: A wellbore tool for locating a target wellbore containing a conductive member from a second wellbore and directing the trajectory of the second wellbore relative to the target wellbore includes an electric current driver having an insulated gap; a three-axis magnetometer positioned within a non-magnetic housing that is disposed within a non-magnetic tubular, the three-axis magnetometer positioned below the electric current driver; a drill bit positioned below the three-axis magnetometer; a hollow tubular connected between the electric current driver and the three-axis magnetometer; and a measurement-while-drilling tool. The current driver generates an electric current across the gap to the portion of the tool below the insulated gap. In a method a current is generated across the insulated gap to the portion of the tool below the insulated gap to the conductive material in the target wellbore returning to a portion of the bottom hole assembly above the insulated gap thereby producing a target magnetic field.

Abstract: A sonde assembly of the invention includes: a sonde housing in the form of a non-magnetic tube having windows therein for permitting a radio signal to be transmitted out the tube from the inside; means such as a device enclosing a front end of the tube; a sonde slidingly disposed inside the non-magnetic tube and closely fitting in a sonde cavity thereof in engagement with a front end stop of the tube. The sonde comprises a sensor and a radio transmitter connected to the sensor to transmit a directional signal based on sensor input, which sensor and transmitter are disposed inside a non-magnetic cylinder.

Abstract: A method for drilling substantially parallel twin wells includes drilling a first well and deploying a casing string in the first well. A magnetized section of the casing string includes a plurality of magnetized wellbore tubulars having at least one pair of opposing magnetic poles located between longitudinally opposed ends of the wellbore tubular. A portion of a second well is drilled within sensory range of magnetic flux from the magnetized section of the casing string. The local magnetic field is measured in the second well and processed to determine a direction for subsequent drilling. Drilling proceeds along the direction for subsequent drilling.

Abstract: A method and apparatus for characterizing a three phase transformer (3) using a single phase power supply (1). Pairs of input terminals (H0-H3) of the transformer are sequentially energized for each energization and the voltage between pairs of output terminals (x0-x3) of the transformer are measured. Measured voltages are processed in order to characterize the winding configuration of the transformer. Either simultaneously or subsequently the presence of neutrals on the primary and/or secondary side of the transformer are identified to enable the winding configuration to be further characterized. Subsequently any phase displacement of the transformer is determined.

Abstract: A method for estimating a property of an earth formation in a zone of investigation, the earth formation having the zone of investigation and another zone, the method including: applying a compound pulse of electromagnetic energy to the earth formation, the compound pulse having a shape to induce a predominately greater amount of current in the zone of investigation than in the another zone, wherein the compound pulse includes a first pulse and a second pulse, the first pulse having an amplitude different from the amplitude of the second pulse; receiving a response of electromagnetic energy from the current induced by the compound pulse; and estimating the property from the response of electromagnetic energy.

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 wireline apparatus for deep well measurements in a borehole being drilled includes a drill string having multiple drill pipe sections connected end-to-end, with at least one of the drill pipe sections being electrically conductive and isolated to provide an electrode section. A nonmagnetic drill pipe section is connected in the drill string below said electrode section, and a hydraulic motor having a rotatable drill bit carrying a drill bit instrument sub having a magnetic field sensing instrument package is connected to a lowermost end of the drill string. A wireline locatable within said drill string incorporates an electrode locatable within the drill pipe electrode section, and carries at its distal end a wireline instrument package that is locatable within the nonmagnetic drill pipe section to receive data representing magnetic field data from the magnetic field sensing instrument package.

Abstract: Methods and related systems are described for making electromagnetic measurements of a subterranean rock formation through a conductive casing of a borehole. A number of transmitters/receivers are deployed into single well having a conductive casing. A magnetic field is induced through the conductive casing and into a surrounding subterranean rock formation, and the magnetic field is detected by the receivers. The receivers have main windings, feedback winding and bucking windings. One of the receiver coils in the tool string is excited at a time, and induced voltages at all of the other receiver coils, either in straight mode, or in feedback mode, are measured.

Abstract: A method for magnetizing a wellbore tubular includes a positioning a wellbore tubular substantially coaxially in a plurality of longitudinally spaced magnetizing coils deployed on a frame. The coils are selectively connected and disconnected from electrical power such that a circumferential electrical current flows in each of the coils to impart a predetermined magnetic field pattern to the tubular. Exemplary embodiments of this invention provide for semi-automated control of tubular magnetization and thereby enable a repeatable magnetic pattern to be imparted to each of a large number of wellbore tubulars.

Abstract: A method and system for identifying a location of a magnetic field source. A total magnetic field is measured during a calibration routine prior to a drilling procedure. During the drilling procedure, a magnetic field measurement is obtained. Using a ratio of the measured magnetic field and the calibrated field, a set of possible angles and distances is calculated. After the source is advanced a known distance, a second magnetic field measurement is obtained. A second ratio is calculated and a second set of possible angles and distances is calculated. The relative location of the source is then determined using the first set and second set of values, along with the known distance and a pitch angle of the source.

Abstract: An instrument for measuring a property of a subsurface material, the instrument including: a magnetic material surrounding a volume in at least two dimensions; and a receiver adapted for receiving energy related to the property of the subsurface material; wherein the receiver is disposed at an exterior surface of the magnetic material.

Abstract: A method for magnetizing a wellbore tubular is disclosed. The method includes magnetizing a wellbore tubular at three or more discrete locations on the tubular. In exemplary embodiments the magnetized wellbore tubular includes at least one pair of opposing magnetic poles located between longitudinally opposed ends of the tubular. Wellbore tubulars magnetized in accordance with this invention may be coupled to one another to provide a magnetic profile about a section of a casing string. Passive ranging measurements of the magnetic field about the casing string may be utilized to survey and guide drilling of a twin well. Such an approach advantageously obviates the need for simultaneous access to both wells.

Abstract: A method for determining the distance and/or direction of a second earth borehole with respect to a first earth borehole, includes the following steps: providing, in the first borehole, first and second spaced apart magnetic field sources; providing, in the second borehole, a magnetic field sensor subsystem for sensing directional magnetic field components; activating the first and second magnetic field sources, and producing respective first and second outputs of the magnetic field sensor subsystem, the first output being responsive to the magnetic field produced by the first magnetic field source, and the second output being responsive to the magnetic field produced by the second magnetic field source; and determining distance and/or direction of the second earth borehole with respect to the first earth borehole as a function of the first output and the second output.

Abstract: A method and system for mitigating risk of well collision in a field includes receiving an anti-collision standard exemption request containing a description of risk of collision between a subject well and one or more offset wells, generating an assessment of the anti-collision standard exemption request using a stored multidimensional decision matrix, reviewing the assessment, and selectively updating the decision matrix based on the review.

Abstract: A method for magnetizing a wellbore tubular includes magnetizing the tubular at three or more discrete locations on the tubular. In exemplary embodiments the magnetized wellbore tubular includes at least one pair of opposing magnetic poles located between longitudinally opposed ends of the tubular. Wellbore tubulars magnetized in accordance with this invention may be coupled to one another to provide a magnetic profile about a section of a casing string. Passive ranging measurements of the magnetic field about the casing string may be utilized to survey and guide drilling of a twin well. Such an approach advantageously obviates the need for simultaneous access to both wells.

Abstract: A method for magnetizing a wellbore tubular is disclosed. The method includes magnetizing a wellbore tubular at three or more discrete locations on the tubular. In exemplary embodiments the magnetized wellbore tubular includes at least one pair of opposing magnetic poles located between longitudinally opposed ends of the tubular. Wellbore tubulars magnetized in accordance with this invention may be coupled to one another to provide a magnetic profile about a section of a casing string. Passive ranging measurements of the magnetic field about the casing string may be utilized to survey and guide drilling of a twin well. Such an approach advantageously obviates the need for simultaneous access to both wells.

Abstract: A method of correcting accelerometer and magnetometer measurements made in a well, comprising: making a series of triaxial measurements with magnetometers and accelerometers in an interval of the well to derive measured values of gravitational acceleration g, magnetic filed intensity B and the sine of the magnetic inclination sinl; obtaining known values of g, B and sinl for the interval; determining values of a correction to be applied to the measured values by simultaneously minimising the difference between the measured values and the known values of g, B and sinl for the interval; and applying the correction to the measured values to obtain in situ corrected values for g, B and sinl.

Abstract: A pair of elongated crossed coils is deployed in a first borehole and an instrument containing magnetic field sensors is deployed in a second borehole. The crossed coils are energized in quadrature by AC currents producing a rotating, elliptically polarized magnetic field at the second borehole. Mathematical analysis of the magnetic field sensor readings determines the location of the second borehole relative to the first. Both the distance and the rotational direction to the second borehole are determined as a function of depth of the sensors relative to that of the pair of crossed coils. Twisting of the long coil in the borehole is evaluated and the relative distance between the boreholes and the corrections needed due to such twisting are determined.

Abstract: A method of locating a conductive target from a wellbore includes generating a current flowing across an insulated gap in a downhole tool positioned in the wellbore, measuring an azimuthal magnetic field with at least one external magnetometer located proximate the exterior of the downhole tool, measuring a secondary magnetic field using a magnetometer disposed inside the downhole tool, computing at least one of a direction and a distance to the conductive target.

Abstract: Reservoir fractures are characterized directly in situ without need to acquire and analyze formation sample cores. A magnetic fluid is injected into an isolated section of the reservoir. The magnitude and directional properties of the enhanced magnetic susceptibility in the section where magnetic fluid injection occurs is measured with a down hole magnetometer. Logs obtained of the enhanced magnetic susceptibility are analyzed to characterize fractures, and petrophysical properties of interest, such as porosity, permeability, and permeability anisotropy of the formation in the vicinity of the fluid injection.

Abstract: An apparatus for obtaining tool face angles on a rotating drill collar in substantially real time is disclosed. In one exemplary embodiment the apparatus includes a magnetoresistive magnetic field sensor deployed in a tool body. The apparatus further includes a programmed processor configured to calculate tool face angles in substantially real time from the magnetic field measurements. The programmed processor may optionally further be configured to correlate the calculated tool face angles with logging while drilling measurements for use in borehole imaging applications.

Abstract: Tracking a boring tool is performed within an underground region using a locating signal. The boring tool is moved through the ground during a series of distance movements such that potential movement of the boring tool during any one of the distance movements is less than a maximum movement value. A current positional relationship is determined for a current one of the distance movements based on: a last-determined positional relationship established for an immediately preceding one of the distance movements, certain orientation parameters, the maximum movement value and the determined signal strength of the locating signal in the current positional relationship. Target coordinates are accepted and a target position, based on the target coordinates, is included as part of the current positional relationship. The position of the target is unconstrained with respect to system geometry. Steering command features are provided along with steering warnings.

Abstract: An azimuthally sensitive logging while drilling tool is disclosed. The tool may be suitable, for example, to measure azimuthal variations of electrical properties of a subterranean formation. The tool includes at least one transmitter disposed to transmit electromagnetic energy and a longitudinally spaced receiver array. The receiver array includes a plurality of discrete magnetic field sensors deployed about a circumference of the tool body. In one exemplary embodiment, the tool includes six or more magnetic field sensors selected from either giant magnetoresistive sensors or anisotropic magnetoresistive sensors.

Abstract: Aspects of this invention include a downhole tool having first and second members disposed to translate substantially linearly with respect to one another. A magnet is deployed on the first member and a plurality of magnetic field sensors is deployed on the second member. The magnetic field sensors are spaced in a direction substantially parallel with a direction of translation between the first and second members. The tool typically further includes a controller disposed to determine a linear position of the first and second members with respect to one another from magnetic flux measurements made at the magnetic field sensors. Exemplary position sensor embodiments of the present invention are non-contact and therefore are not typically subject to mechanical wear. Embodiments of the invention therefore tend to advantageously provide for accurate and reliable linear position measurements.

Abstract: This disclosure, in one aspect, provides an apparatus for use in a wellbore that includes a member having an encoded magnetic field and a sensor proximate the encoded magnetic field that measures a change in the magnetic field due to a change in the load on the member. In another aspect, a method for measuring loads on a downhole tool is provided that comprises inducing an encoded magnetic field along a section of a member of the tool and detecting a change in the magnetic field due to a load on the member when the tool is in the wellbore.

Abstract: The present invention provides a novel use of a material having a high internal magnetostrictive damping and/or using material with explicitly low magnetostriction as an antenna core material for NMR and resistivity devices in a borehole. The probe stuctural geometry facilitates the use of material, which has a relatively low magnectic permeability.

Abstract: Measurement of the location and direction of a drill head in a borehole extending beneath an obstacle such as a body of water utilizes a single AC solenoid at a known location but having an unknown orientation. The measurements are used to direct the path of the borehole.

Abstract: A sensor for measuring mud resistivity in a borehole includes a transmitter having a magnetic moment in a first direction; and a receiver having a magnetic moment in a second direction, wherein the first direction and the second direction are substantially different, wherein the transmitter and the receiver are disposed in an insulating collar of a downhole tool, and wherein the transmitter is disposed at a selected distance no more than 10 inches from the receiver along a longitudinal axis of the downhole tool.

Abstract: The invention relates to measuring equipment and method for mapping the geology including a transmitter circuit with a current source for generating an electric current and a transmitter coil; a switch for connecting the current source to the transmitter coil during operation so that an electric current is generated in it, with the current building up a magnetic field in the formation, and for cutting off this current again so that the built-up magnetic field in the formation decays; and a receiving circuit with a receiving coil for registering the voltage induced over the receiving coil. There is a preamplifier for amplifying the registered voltage (VRcoil) from the receiving coil and the second electrical switch for disconnecting the connection between the receiving coil and the preamplifier, a measuring equipment can be provided that is so compact that it can be used for airborne transient sounding.

Abstract: An induction logging tool is used on a MWD bottom hole assembly. Due to the finite, nonzero, conductivity of the mandrel, conventional multi frequency focusing (MFF) does not work. A correction is made to the induction logging data to give measurements simulating a perfectly conducting mandrel. MFF can then be applied to the corrected data to give formation resistivities.

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: The present invention relates to the processes and devices for assessing the permeability of a rock medium 1 containing a fluid 2 in its interstices 3. The device and the process according to the invention are characterized essentially in that a given magnetic field is applied to the interstitial fluid 2 located in the rock medium 1, the variation in pressure of the interstitial fluid 2 resulting from the application of the magnetic field is measured, and the permeability of the rock medium is determined as a function of the value of the variation in pressure of the interstitial fluid.

Abstract: A method for forming one or more openings in a hydrocarbon containing formation is described. The method may include forming or providing a first opening in the formation. A plurality of magnets may be provided into the first opening. The plurality of magnets may be positioned along a portion of the first opening. The plurality of magnets may produce a series of magnetic fields along the portion of the first opening. A second opening in the formation may be formed using magnetic tracking of the series of magnetic fields. The second opening may be spaced a desired distance from the first opening. Alternate embodiments include use of an energized conduit to create a magnetic field. Such energized conduit can be used alone or with the plurality of magnets.