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: 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: Calibration of the arrays of a multicomponent induction logging tool is achieved by positioning the tool horizontally above ground. The upper and lower housings of the tool are connected by a borehole conductivity simulator which as a resistance comparable to that of a borehole. Axial and radial positioning of the transmitter coils is done by monitoring outputs at receiver coils to achieve a minimum.

Abstract: A method for estimating resistivity of a formation includes exciting an alternating current in the formation through non-conductive mud within a bore hole in the formation using a circuit. The circuit includes a known inductor and the non-conductive mud. A circuit response is measured. The complex impedance of the circuit is computed using the measured response to estimate the resistivity of the formation.

Abstract: The present invention provides a compact magnetic sensor capable of use in pad mounted applications and field focusing applications. The present invention provides an induction tool with a compact induction sensor having electromagnetic transmitters wound on a longitudinal core member of a C-clamp shaped transmitter core. The tool is suitable for transmitting magnetic excitation fields in multiple directions, both parallel and transverse to the tool's longitudinal axis with minimal susceptibility to errors associated with parasitic eddy currents induced in the metal components surrounding the transmitter and receiver coils. The horizontal (transverse) members of the C-clamp shaped transmitter core can be rotated to orient a magnetic excitation flux path passing between the horizontal (transverse) members and through the formation. The horizontal members can be replicated on a single longitudinal member to shape the flux path.

Abstract: A suspended well logging apparatus is provided having downhole well data acquired by a sensor, transmitted to the surface via complementary modems, and conveyed to the surface modem via a data transmission cable linking the modems, the cable having at least one twisted pair of signal conductors positioned within an outer protective sheath, each of the conductors being separately insulated, the at least one twisted pair of signal conductors having a twist rate of at least ? twist per inch, an insulation sheath surrounding the twisted pair of conductors and a tensile load carrier surrounding the insulation sheath, the load carrier comprising a sheath of tensile load carrying filaments enabling self support of the well logging cable.

Abstract: A measurement and communication system for use with a tubular string, comprises a tubular string having a plurality of self-powered, autonomous telemetry stations disposed at predetermined locations along the tubular string. Each autonomous telemetry station is adapted to receive at least one first signal and transmit at least one second signal related to the at least one first signal. Power is extracted from potential energy sources proximate each autonomous telemetry station. A method of communicating information along a tubular string comprises, disposing an autonomous telemetry station at predetermined locations along the tubular string. A preferred transmission path is autonomously determined at each of the autonomous telemetry stations. Information is transmitted along the tubular string according to the autonomously determined preferred path.

Abstract: A magnetic coupling for substantially synchronously transferring linear motion through a non magnetic barrier from a first movable element to a second movable element. The coupling comprises magnets disposed at spaced apart locations along the first element. The magnets each have a magnetization direction substantially perpendicular to a direction of motion of the first element along the non magnetic barrier. The coupling includes magnets disposed at spaced apart locations along the second element at locations corresponding to locations of the magnets op the first element. Each of the magnets on the second element has a magnetization direction inclined at an oblique angle with respect to the magnetization direction of the corresponding magnet so as to capture magnetic flux from the magnets on the first element when either of the elements is moved along the barrier.

Abstract: A well logging instrument string including a first section adapted to be operated substantially in contact with a wall of a wellbore, a coupling connected at one end to one end of the first section. The coupling includes first and second flexible joints for enabling relative angular deflection between the first section and a second section. The coupling includes a biasing mechanism for urging at least one of either the first or the second flexible joints, or both, to assume their positions of maximum angular deflection. The instrument string includes a second section connected to the other end of the coupling. The second section is adapted to be operated spaced apart from the wellbore wall.

Abstract: An apparatus and method for detecting the location of subsurface markers in a formation proximate to a borehole. The apparatus includes marker detectors in a housing having at least two housing sections attached in an initial orientation. The distance between the detectors is measured under controlled conditions with a calibration bar. The initial attached orientation between the housing sections is identified with a calibrator, and deviations from the initial attached orientation are identified by the calibrator after the housing sections are detached and reattached. The calibrator permits well site corrections to be made to the housing sections without recalibration. Gauges permit corrections for temperature and pressure fluctuations, and the corrected distances between the housing detectors is computed.

Abstract: An apparatus (sonde) and method of measuring density, or gravel pack quality, in a cased well borehole using a fast neutron source and one or more thermal neutron detectors is described. In one embodiment, a neutron source creates a fast neutron flux which reacts primarily with the material within the borehole casing while a collocated neutron detector counts the number of backscattered thermal neutrons. A novel means of obtaining azimuthal measurement discrimination is provided by a rotating neutron shield. In one instance the shield is quite substantial, creating a narrow measurement window. In another instance, the shield only marginally screens the detector, creating a large measurement window. In an alternative embodiment, a second thermal neutron detector is spaced distally from the neutron source and first detector.

Abstract: An optical fiber quick disconnect mechanism comprised of left and right separable portions is set forth. One portion is ideally anchored to a pressure isolating bulkhead at a drilled passage which is provided with threads partly along its length; a fixed portion of the quick disconnect mechanism can be anchored there. This enables division of an optical fiber into left and right portions which provide an optical path therethrough. The left and right optical portions are supported by alignment capillaries and the detachable portion of the equipment includes a threaded body which joins to the fixed portion.

Abstract: This disclosure is directed to a detector system for use in measuring while drilling (MWD) equipment. It comprises preferably duplicate chambers positioned to one another and mounted in a MWD system where they are subject to the same shock and vibration. The shock and vibration impinge on the two chambers, and cause two output signals to be formed. The two output signals are applied to a differential amplifier so that the microphonic portion of the signal is cancelled. This then leads to a differential output signal which carries in it the signals representing nuclear events detected by the similar or duplicate detector means. Alternately, a single chamber can be used if it is provided with two anode wires and they are connected to the differential amplifier for signal cancellation.

Abstract: For use in a downhole oil well logging tool which is enclosed in a sonde and suspended on an armored logging cable, a means for measuring the macroscopic thermal neutron capture cross section of the borehole fluid is set forth. In the preferred embodiment, a neutron source adjacent to a neutron detector is positioned in a sonde. The entire surrounding region in the well borehole is used as a sample chamber. Fast neutrons from the source after collision with fluid nuclei impinge on the detector which provides an output signal which is indicative of neutron flux. The count rate is most significantly dependent on the thermal neutron capture cross section of the borehole fluid. An additional detector can likewise be spaced farther from the neutron source and provide an alternate count rate. Through the use of two detectors, minor perturbations induced by changes in the environment outside the borehole can be compensated. The neutron capture cross section can be determined for the borehole fluid.

Abstract: A measuring device for use in a producing well is set forth. It includes a sonde having upper and lower centralizers to define an annular flow space therearound. In the preferred embodiment, a motor driven sensor preferably a piezoelectric combination transmitter and receiver is, included to transmit and then receive ultrasonic pulses. They are transmitted downwardly from the housing into fluid flowing in the well. Reflective interfaces are defined by material differences. Gas bubbles droplets and particles in the fluid flow and phases between oil and water, etc. form reflective interfaces to create a scattering effect to transmitted ultrasonic pulses so that a return pulse is formed. The pulses encodes fluid flow velocity as a result of the Doppler shift.

Abstract: An optical rotary joint for use in a well logging cable is set forth in the preferred and illustrated embodiment capable of transferring two or more data streams traveling along two or more optical fiber channels. The rotary joint is constructed with a stationary portion and a coacting rotary portion. A first channel of data is delivered to an optical fiber transmitted coaxially of the stationary and rotary sides of the apparatus, transfer across the rotational plane between the two components being accomplished by opposing centrally located, concentrically arranged, coacting optical lenses. A second data channel transmitted through a second optical fiber is delivered to a lens system which converts the light into a cylinder of light coaxial with the first channel and which surrounds the optical management for the first channel. All channels other than the first channel thus are converted into coaxial hollow cylinders of light.

Abstract: For use in measuring thermal neutron activity in an open or cased hole, the preferred and illustrated embodiment of the present apparatus sets forth a porosity tool. The device incorporates one or more thermal neutron detectors in a sonde having a pressure housing adapted to be lowered into a borehole. The thermal neutron detector(s) is decentralized by placing it adjacent to one side of the pressure housing, and a decentralizer spring is placed on the exterior of the housing opposite the detector; this locates the detector much closer to the formation and reduces the intervening borehole fluid and the impact of borehole geometry on the data so obtained. Moreover, the decentralized detector is protected on the side of the detector away from the formation by placing a shield reducing the thermal neutron flux from that direction toward the detectors. In the preferred embodiment, the shield is cadmium and forms an approximate semi-cylinder about the detector.

Abstract: In the preferred and illustrated embodiment salinity measuring apparatus is disclosed. An elongate sonde has a housing with an internal chamber. The chamber is perforated by opening to the exterior to introduce well fluid. Transverse plates define the chamber and mount the acoustic transducer which sends an acoustic pulse along the chamber. An acoustic transceiver is coupled to a timer circuit which determines changes in transit time as a function of salinity compared to pure water.