Abstract: A dipole acoustic well logging instrument including an acoustic transmitter. Receiver sections are disposed at axially spaced apart locations from the acoustic transmitter. Each receiver section includes an outer shoulder at each end adapted to be placed in acoustically isolated contact with an internal shoulder of a connector coupling when the instrument is in tension. The outer shoulders have an acoustically isolating material disposed on their surfaces. The receiver sections include an inner shoulder at each end adapted to be placed in direct contact with an external shoulder of the connector coupling when the instrument is in compression. The instrument includes one connector couplings disposed at each end of each receiver section to couple the receiver sections to each other and to the remainder of the instrument. At least one receiver element is disposed in a passage formed into each of the receiver sections.

Abstract: A computationally economical method for applying multi-dimensional multiple-reflection attenuation to a marine seismic-signal data set comprised of a plurality of common shot gathers that have surface-multiple wavefields embedded therein. The multi-dimensional data are assumed to have been gathered from a plurality of parallel 2-D lines of survey. From every nth reference line, where n is a small number greater than 2, a common shot gather is selected. For every so-selected common shot gather, a reference surface-multiple wavefield is predicted as a function of offset and travel time with the aid of any well-known multiple attenuation routine, using a wavelet having fixed attributes in terms of amplitude, phase and frequency. A common shot gather is chosen from among the plurality of common shot gathers.

Abstract: A distributed seismic data acquisition system includes a vast plurality of Autonomous Data Acquisition Modules (ADAM) to each of which are interconnected a subplurality of data-collection channels. Each data collection channel is comprised of an array of seismic sensors for continuously measuring seismic signals. The ADAMs include a GPS satellite receiver for providing geographic coordinates and system clock. Measured seismic signals are quantized and continuously downloaded to the respective interconnected ADAMs from the data-collection channels. The system includes both field testing capability as well means for transmitting the results of self tests. Provision is made for servicing the ADAMs at the end of a multi-day recording session and for harvesting and cataloging the recorded data. The seismic signals gathered by use of the distributed data-gathering system may be processed to provide a subsurface earth model.

Abstract: A downhole acoustic logging tool having a random access memory for storing acoustic waveforms in digital format. The waveforms being transmitted from a surface logging system to the random access memory in the downhole logging tool. The logging tool playing back the stored waveforms by converting the stored digital format into an analog signal that is amplified sufficiently for driving an acoustic transmitter. A received pilot signal is used to determine the signal attenuation of the logging cable and a correction is made therefrom to the actual received acoustic signal. Complex waveform types may be programmed into the random access memory for specific formation characteristics. Tapered turn-on and turn-off of the signal waveform amplitudes reduce higher frequency spectral noise that may interfere when correlating the received acoustic signal with the transmitted acoustic signal.

Abstract: An array of output image points is distributed over a velocity model of a subsurface region of interest. A fan of rays is shot from each of a plurality of acoustic source points along the surface, the angular separation between the rays being equal to .pi./n, where n is the number of rays. A family of traveltime wavefronts is erected at selected time intervals, .DELTA.t, along the ray trajectories. The resulting wavefront map is superimposed over the array of output image points. Sub-arrays of output image points will lie within discrete traveltime cells, the widths of which are defined by the separation between adjacent rays paths and the heights are defined by the wavefront separation distance. Ray segments, wavefront segments and output image points are identified by a velocity layer index. A velocity interface that may cut across a traveltime cell, divides the cell into two parts, each having a different layer index.

Abstract: A marine seismic surveying method recording with a first sensor a first signal indicative of pressure and with a second sensor a second signal indicative of motion, calculating a coupling mechanism filter for the second signal substantially correcting for the imperfect coupling of the second sensor, and applying a filter based on the coupling mechanism filter to at least one of the signals.

Abstract: A receiver consistent deconvolution operator models the damped oscillatory wavetrain that is related to geophone coupling to the water bottom. The operator is a best-fitting function that endeavors to describe the difference in coupling response between a well-coupled in-line geophone relative to an imperfectly-coupled cross-line geophone. The operator is applied to the cross-line signals to compensate the signals for the distortion due to imperfect cross-line ground coupling.

Abstract: A method for minimizing non-uniform insonification of subsurface formations in the presence of steep dips when advancing a swath of elongated parallel seismic streamer cables along a line of survey. A first acoustic source is stationed at the leading end of the swath and a second source is stationed at the trailing end of the swath. The sources are activated in alternate cycles at preselected timed intervals to provide down-dip and up-dip seismic data sets. The data sets are processed and merged to eliminate objectionable shadow zones.

Abstract: A nuclear magnetic resonance apparatus including a magnet generating a static magnetic field in a first region containing materials to be analyzed. The magnet generates zero static magnetic field in a second region. The magnet has generally homogeneous magnetization along a longitudinal axis and is magnetized substantially perpendicular to the axis. The apparatus includes means for generating a radio frequency magnetic field in the first region for exciting nuclei of the materials. The means for generating the radio frequency magnetic field includes an antenna disposed within the second region. The apparatus includes means for receiving a nuclear magnetic resonance signal from the excited nuclei. The means for receiving also provides an output indication of properties of the materials to be analyzed. In a preferred embodiment, the means for generating and receiving include an antenna at least partially disposed within the second region.

Abstract: A method for determining orientations and velocities of slow and fast waves in an anisotropic earth formation. Signals are used from an acoustic logging tool including dipole transmitters and receiver arrays. An initial value of angle subtended between orientation of the fast wave and one of the transmitters is selected. A waveform of a fast principal wave and slow principal wave at first and second selected receiver positions are calculated from received signals at each of these positions and the selected subtended angle. A derivative waveform with respect to subtended angle is calculated for both fast and slow principal waves. An initial velocity of slow waves is selected and the calculated waveforms of the slow principal wave and its derivative waveform at the first position are time shifted by a time corresponding to distance between first and second receiver positions and the selected value of velocity.

Abstract: An electromagnetic wellbore logging tool including an elongated sonde adapted for traversing the wellbore, a source of alternating current, an antenna connected to the source of alternating current, and a receiver circuit connected to the antenna. The receiver circuit provides an output corresponding to electromagnetic signals induced in the antenna. The invention includes at least one insulating insert disposed in an annular space between the exterior of the sonde and the wall of the wellbore. The insert extends in a direction so as to segment the paths of eddy current which would otherwise flow in the annular space. In a preferred embodiment, the logging tool includes a nuclear magnetic resonance apparatus having a longitudinal dipole antenna. The insulating inserts extend along the longitudinal axis of the tool so as to segment eddy current paths perpendicular to the longitudinal axis of the tool.

Abstract: The invention is a method of determining the permeability of an earth formation using a wireline formation testing instrument. The method includes measuring pressure with respect to time at a probe in hydraulic communication with the earth formation, calculating time derivatives of the measured pressure, withdrawing fluid from the earth formation by increasing a volume of a chamber in hydraulic communication with the probe, measuring the volume of the chamber with respect to time, and calculating time derivatives of the measured volume. Increasing the volume of the chamber is stopped. The permeability is calculated when the measured pressure substantially stops increasing, by determining a slope of a linear relationship of the measured pressure with respect to a fluid flow rate calculated from the time derivative of the volume and the time derivative of the pressure.

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: A method of determining amplitude and phase response of a receiver amplifier in an induction well logging instrument including the steps of generating an oscillating current at least one frequency, energizing a transmitter coil instrument with the oscillating current, generating a first test signal having a known phase and amplitude relationship with respect to the oscillating current and a different frequency than any frequency in the oscillating current, amplifying and detecting voltages induced in a receiver coil corresponding to electrical properties of an earth formation, conducting a portion of the first test signal to the receiver amplifier causing the amplifier to generate a combined output including the first test signal and a signal resulting from the induced voltages, combining the oscillating current with the first test signal to form a combined test/reference signal, spectrally analyzing the combined test/reference signal and spectrally analyzing the combined output, and comparing spectral analys

Abstract: The invention is a method of inversion processing signals from an induction well logging instrument including a transmitter and a plurality of receivers at spaced apart locations. The method includes skin effect correcting the responses of the receivers by extrapolating the receiver responses to zero frequency. A model is generated of the media surrounding said instrument. Conductivities of elements in the model are then adjusted so that a measure of misfit between the skin-effect corrected receiver responses and simulated receiver responses based on the model is minimized. The geometry of the model is then adjusted so that the measure of misfit between the skin-effect corrected receiver responses and the simulated receiver responses based on the model is further minimized.

Abstract: A method of measuring motion properties of nuclei within pore spaces of a porous medium. The method includes applying a static magnetic field to the medium to polarize the nuclei, generating a first magnitude of magnetic field gradient within the pore spaces of the medium, applying a radio frequency magnetic field to excite the nuclei, receiving nuclear magnetic resonance signals from the nuclei, and calculating the motion properties from rates of decay of the amplitude of the nuclear magnetic resonance signals.

Abstract: A high-order polynomial regression curve is fitted to a global set of first arrival times as a function of the nominal ranges between a plurality of acoustic sources having known geodetic coordinates and a plurality of acoustic detectors whose coordinates are imperfectly known. The order of the polynomial is chosen to be that order that minimizes the variance of the parameters about the regression curve. The polynomial is used as a quasi-velocity function for iteratively optimizing the best estimate of the ranges between each detector and every source station. The best estimate of the detector position is derived by multi-lateration using the computed ranges.

Abstract: An adjustable valve for controlling fluid flow between an inlet and an outlet in a valve. A compressed spring biases a valve member against the valve inlet to prevent fluid flow until the fluid pressure reaches a certain level. One end of the spring contacts a hydraulic plunger which is moved with a hydraulic fluid. The hydraulic fluid pressure can be raised to increase the spring force acting against the valve element, and the hydraulic fluid pressure can be reduced to decrease the spring force acting against the valve element. The flow rate at the valve outlet can be monitored, and flow rate signals can be transmitted to a controller for adjusting the hydraulic fluid pressure in response to the flow rate detected.

Abstract: A plurality of sensors, each of which is coupled to a data channel, are mounted on a downhole logging tool for periodically measuring and sampling, at preselected timed sample intervals, petrophysical characteristics of the borehole sidewall material. The sample values are arranged in a two-dimensional array of a plurality of time series in channel-sequential order, indexed by consecutive sample number. Means are provided for transforming the plurality of time series from the time domain to the wavelet domain. The wavelet coefficients for each transformed time series are compressed by thresholding. The compressed wavelet coefficients corresponding to each time series are transmitted to a receiver where the compressed wavelet coefficients are decompressed by formatting same into a broken sequence of wavelet coefficients. The original time series is reconstructed by inversely transforming the broken sequence of wavelet coefficients from the wavelet domain back to the time domain.

Abstract: An apparatus for measuring the resistivity of earth formations penetrated by a wellbore having a conductive conduit. The apparatus includes an elongated sonde mandrel, a plurality of electrodes positioned at axially spaced apart locations along the mandrel, the electrodes being electrically insulated from the mandrel and from each other, the electrodes adapted to electrically contact the conduit and positioned collinearly so that the electrodes contact the conduit when the mandrel is radially displaced towards the wall of the conduit. Some electrodes are for injecting electrical current into the conduit, other electrodes are for measuring voltage drop along the conduit at axially spaced apart locations. The mandrel includes selectively extensible locking arms for urging the mandrel into contact with the conduit. The arms are radially positioned opposite to the electrodes.