Abstract: An electromagnetic wave propagation resistivity borehole logging system comprising multiple groups of electromagnetic transmitter-receiver arrays operating at three frequencies. The borehole logging tool component of the system employs eight transmitters and four receivers. The transmitters and receivers are disposed axially and symmetrically along the major axis of the tool to form four group pairs. Each group pair consists of a transmitter-receiver groups axially and symmetrically on opposing sides of a reference point on the tool. Each, transmitter-receiver group consists of one transmitter assembly and two receiver assemblies. Each transmitter-receiver group is operated at two of three operating frequencies which are 100 kHz, 400 kHz and 2 MHz. The transmitter and receiver assemblies are fabricated to yield azimuthally symmetrical resistivity measurements in a plane essentially perpendicular to the axis of the tool.

Abstract: An electromagnetic wave propagation resistivity borehole logging system comprising multiple groups of electromagnetic transmitter-receiver arrays operating at three frequencies. The borehole logging tool component of the system employs eight transmitters and four receivers. The transmitters and receivers are disposed axially and symmetrically along the major axis of the tool to form four group pairs. Each group pair consists of a transmitter-receiver groups axially and symmetrically on opposing sides of a reference point on the tool. Each, transmitter-receiver group consists of one transmitter assembly and two receiver assemblies. Each transmitter-receiver group is operated at two of three operating frequencies which are 100 kHz, 400 kHz and 2 MHz. Some of the transmitter and receiver assemblies are fabricated to yield azimuthally focused resistivity measurements, and to yield vertical and horizontal resistivity in anisotropic dipping beds.

Abstract: An NMR apparatus includes permanent magnets oppositely polarized in the axial direction and suitably arranged along the axis of the apparatus to produce a nearly radial static magnetic field in a toroidal examination region within the rock formation surrounding the wellbore. A first coil is wound around a cylindrical annulus core coaxial with the magnets, the core including high magnetic permeability material. The first coil produces pulsed RF magnetic fields oriented parallel to the axis of the apparatus and thus perpendicular to the static magnetic field in the toroidal examination region. This reorients certain nuclear spins and the bulk magnetization of the formation within the examination region resulting from them. The first coil picks up on component of the spin-echo signals of the precessing nucleii.

Abstract: An NMR apparatus includes permanent magnets oppositely polarized in the axial direction and suitably arranged along the axis of the apparatus to produce a nearly radial static magnetic field in a toroidal examination region within the rock formation surrounding the wellbore. A first coil is wound around a cylindrical annulus core coaxial with the magnets, the core including high magnetic permeability material. The first coil produces pulsed RF magnetic fields oriented parallel to the axis of the apparatus and thus perpendicular to the static magnetic field in the toroidal examination region. This reorients certain nuclear spins and the bulk magnetization of the formation within the examination region resulting from them. The first coil picks up on component of the spin-echo signals of the precessing nucleii.

Abstract: A highly accurate, fully compensated, high spatial resolution, wave propagation system for measuring dielectric constant and resistivity of fluids or solids in a cylindrical enclosure and method for measuring well core characteristics in-situ or in a laboratory. One embodiment of the invention relies on waves propagated from transmitters above and below two spaced receivers which transmit and receive electromagnetic waves via slots on the inner periphery of a cylinder structure. The data is then processed with a CPU either down hole for later retrieval or on the surface for real-time monitoring.

Abstract: A method and apparatus is disclosed for performing measurement-while-drilling operations in a borehole to interrogate the borehole and the surrounding formation utilizing electromagnetic fields. A measurement sonde is provided which includes at least one of (a) a transmitting member for generating an interrogating electromagnetic field for passage through the borehole and surrounding formation, and (b) a receiving member for receiving an interrogating electromagnetic field after passage through said borehole and surrounding formation. A measurement tubular is provided, which includes a central bore which communicates with the central bore of the drillstring. The measurement tubular couples in the drillstring in a selected location, and permits interrogation of the borehole and surrounding formation with the interrogating electromagnetic fields generated by the measurement sonde.

Abstract: A Measurement-while-Drilling method and apparatus for obtaining information about a formation uses sensors on substantially non-rotating pads attached to a rotating housing that is part of the drilling assembly. The pads make contact with the formation. The sensors may be density, NMR, resistivity, sonic or electromagnetic. The NMR sensors may use a static magnetic field that can be either radial or longitudinal in direction. The resistivity sensors may involve direct measurement of leakage current or may rely on induction methods. The sonic sensors may be three component transmitters and/or receivers for determining compressional and shear velocities of the formation and may also be used to image the formation in a VSP or a reverse VSP. In an alternate arrangement, the sensors rotate with the drill bit. A downhole microprocessor analyzes the data to improve signal-to-noise ratio and to reduce redundancy in the acquired data.

Abstract: An arrangement of two closely spaced transmitters and two spaced apart receivers symmetrically disposed about the transmitters in a measurement while drilling tool avoids the effects of mutual coupling between the receivers. In one method of operation of the transmitters, each transmitter is sequentially activated while the other transmitter is decoupled to eliminate mutual coupling, and the recorded signals processed to take advantage of reciprocity relations. In another method of operation, both transmitters are operated simultaneously with one relative polarity and then with another relative polarity, to eliminate the effects of mutual coupling and to take advantage of reciprocity relations.

Abstract: The present invention is directed to a measurement-while-drilling logging tool which includes a minimum number of analog electrical and electronic components, and which instead utilizes digitally-controlled electronic and electrical components to obtain an accuracy which is not possible utilizing prior art measurement-while-drilling logging tools. Additionally, the present invention allows for calibration operations to be conducted before, during, and after logging operations. Preferably, the calibration operations are performed periodically or intermittently during logging operations, and recorded, to be utilized later in explaining any irregularities in the log data. This calibration operation during drilling operations is not found in prior art devices, and is rendered practical by the utilization of digitally-controlled electrical and electronic components in lieu of analog components which are traditionally utilized in logging tools.

Abstract: A logging apparatus is provided for use in a wellbore for measuring an attribute of at least one of the wellbore and a surrounding formation, when coupled to a wellbore tubular expended in the wellbore. The logging apparatus includes a housing, at least one transmitter, and at least one receiver. The transmitter is carried by the housing and is individually and selectively operable for producing electromagnetic interrogating signal at selected interrogation frequency for passage to the wellbore and surrounding formation. The receiver is carried by the housing in a selected position relative to the transmitter, and is tuned to receive electromagnetic signals at the interrogation frequency to the exclusion of other frequencies.

Abstract: The present invention is directed to a measurement-while-drilling logging tool which includes a minimum number of analog electrical and electronic components, and which instead utilizes digitally-controlled electronic and electrical components to obtain an accuracy which is not possible utilizing prior art measurement-while-drilling logging tools. Additionally, the present invention allows for calibration operations to be conducted before, during, and after logging operations. Preferably, the calibration operations are performed periodically or intermittently during logging operations, and recorded, to be utilized later in explaining any irregularities in the log data. This calibration operation during drilling operations is not found in prior art devices, and is rendered practical by the utilization of digitally-controlled electrical and electronic components in lieu of analog components which are traditionally utilized in logging tools.

Abstract: A method and apparatus is provided for measurement-while-drilling utilizing improved antennas. An elongated tubular member is provided with an outer peripheral surface having a contoured portion defining a plurality of discrete communication regions of reduced radial dimension. An antenna pathway is defined in the elongated member substantially transverse to the plurality of discrete communication regions. An antenna member is partially disposed in the antenna pathway with portions of the antenna member extending out of the elongated member at the plurality of discrete communication regions to facilitate communication of electromagnetic energy. In a reception mode of operation, the antenna member detects electromagnetic energy in the wellbore and generates a current corresponding thereto. If operated in a transmission mode of operation, the antenna member emits electromagnetic energy in the wellbore in response to an energizing current.

Abstract: A logging-while-drilling system is disclosed which includes a pair of receiving antenna disposed between upper and lower transmitting antenna. The upper and lower transmitting antenna are energized successively to generate an electromagnetic wave which propagates through the formation surrounding the borehole. The amplitude attenuation and phase shift of the electromagnetic wave between the receiving antenna is measured. Measurements from both the upper and lower transmitting antenna can be combined to eliminate by cancellation system error components. In order to further improve the performance of the logging-while-drilling system, separate and dedicated driver circuits are provided proximate each transmitter. In addition, reference signals which are utilized to coordinate and synchronize the operation of the various components of the logging-while-drilling system are provided at frequencies which are substantially different from the interrogation frequency of the electromagnetic interrogation signal.

Abstract: A well logging apparatus and method for measuring the resistivity of the formation surrounding a borehole is disclosed. The invention provides two transmitting antennas arranged around a housing means or drill collar in spaced relation from one another. A transmitting circuit alternately supplies an oscillating drive signal to each transmitting antenna with a sufficiently high frequency such that one and then the other of the transmitting antennas radiates an electromagnetic wave signal which propagates through the formation. Two receiving antennas are located equally spaced between the transmitting antennas to produce pick-up signals from the electromagnetic wave propagating through the formation. Each receiving antenna includes a single turn coil connected in series with a capacitor to provide a reduced impedance circuit to resonate in the frequency region embracing the oscillating drive signal.

Abstract: An apparatus and method for measuring formation parameters by transmitting and receiving electromagnetic signals by antennas disposed in recesses in a tubular housing member and including apparatus for reducing the coupling of electrical noise into the system resulting from conducting elements located adjacent the recesses and housing. More particularly, a method and apparatus employing electrostatic, but not magnetic, shielding of the low impedance antenna systems and inductive signal coupling to enhance the signal at the receiver is disclosed. This system is capable of measuring formation parameters in the presence of conducting bodies, e.g., the drill string, permitting incorporation of the apparatus in a measuring while drilling (MWD) logging system. In a particular embodiment, high frequency electromagnetic energy is used to measure formation resistivity.

Abstract: Electrical energy is induced into an earth formation by a transmitter in apparatus, adapted to be passed through a borehole traversing the earth formation. Clock pulses are also provided in the apparatus. At least two receivers provide signals corresponding to received electrical energy from the earth formation. A gating circuit provides groups of clock pulses in accordance with the signals from the receivers so that the number of clock pulses in each group corresponds to the dielectric constant of the earth formation.

Abstract: A system operating at radio frequencies in the range of 10 MHZ to 60 MHZ is provided for simultaneously determining the resistivity and dielectric constant of earth formations in the vicinity of a well bore. A transmitter coil and two longitudinally spaced receiver coils are provided in the system. Circuit means for measuring the unnormalized amplitude ratio and the relative phase shift of electromagnetic waves at the spaced receiver coils are provided. A relationship is given whereby the formation dielectric constant and resistivity may be obtained from the amplitude ratio and relative phase shift measurements.

Abstract: The invention disclosed herein includes methods and apparatus for determining true formation resistivity, flushed zone resistivity and invasion diameter of the earth formation in the vicinity of a well borehole. A radio frequency electromagnetic field in the frequency range from 800 kilohertz to 4 megahertz is generated in a borehole and the electromagnetic field is detected at a plurality of longitudinally spaced locations. Measurements of the attenuation and propagation velocity of the electromagnetic wave at the longitudinally spaced receivers may then be interpreted according to predetermined relationships in terms of the formation resistivity, flushed zone resistivity and invasion diameter surrounding the borehole.

Abstract: A dielectric well logging system includes a logging tool adapted to be passed through a borehole traversing an earth formation. The logging tool includes a transmitter which induces electric energy into the earth formation at a radio frequency. Two receivers in the logging tool spaced a predetermined distance apart provides intermediate frequency signals corresponding to the electrical energy received from the earth formation. The intermediate frequency signals are transmitted by way of a cable to the surface. Surface electronics include zero crossing detectors, each detector receives a different intermediate frequency signal from the cable and provides a detector signal whose change in amplitude is representative of the intermediate frequency signal passing through zero. A source provides clock pulses at a frequency substantially greater than the frequency of the intermediate frequency signals.

Abstract: The invention disclosed herein includes methods and apparatus for determining the resistivity and dielectric constant of earth materials in the vicinity of a well borehole. A radio frequency electromagnetic field in the frequency range from 20 to 40 megahertz is generated in a borehole and the total electromagnetic field at two longitudinally spaced locations is detected. Measurements of the relative phase shift in the field between the detector locations and the amplitude of the field at least at one of the detector locations may then be interpreted according to predetermined relationships in terms of the earth formation resistivity and dielectric constant.