Abstract: This invention provides a method and apparatus for determining position from code modulated, suppressed carrier signals received from satellites, in which a digital composite of the signals received from a plurality of satellites is formed at a first point, the digital composite is processed to measure the carrier phase of the signal from each of the plurality of satellites to derive computer data, and said computer data are combined with data derived from measurements of signals received from the same plurality of satellites at another point, to determine position data.

Abstract: The two-way water-layer travel time, .tau., is derived from duel-mode seismic sensor data by cross-correlating the Fourier transforms of the sum and difference of the velocity and pressure signatures. The Z-transform of .tau. evaluates one of the two Backus variables, Z.sub.w. The second variable is R.sub.b, the water bottom reflectivity coefficient. The frequency-domain transforms of the above summed and differenced signatures are each multiplied by the Backus operator (1+R.sub.b Z.sub.w).sup.2 after initializing R.sub.b and the products are iteratively cross-correlated until the correlation function converges to a minimum. R.sub.b is perturbed after each iteration. The value of R.sub.b upon convergence is the local water bottom reflectivity coefficient.

Abstract: A shaped charge for efficiently transferring energy from an explosive material to generate a deep penetrating jet. The shaped charge liner is formed with a hemispherical first section combined with an elongated second section. The liner second section can be formed as a truncated cone, trumpet, or other shape. The hemispherical first section collapses to generate a high velocity jet portion, and the second section collapses to generate an elongated, deep penetrating jet portion which follows the higher velocity jet portion.

Abstract: A method for controlling the position and shape of marine seismic streamer cables, whereby a plurality of real time signals from a marine seismic data acquisition system and a plurality of threshold parameters from an input device are received. The real time signals are compared to the threshold parameters to determine if the streamer cables should be repositioned. The streamer cables are repositioned when the real time signals exceed the threshold parameters.

Abstract: An apparatus for measuring the porosity of earth formations penetrated by a wellbore. The apparatus includes an elongated housing adapted to traverse the wellbore, a controllable source which emits bursts of high-energy neutrons, a near detector primarily sensitive to thermal neutrons and axially spaced apart from the source, a far detector also primarily sensitive to thermal neutrons and axially spaced apart from the source so that the near detector is axially disposed between the source and the far detector. The apparatus includes a neutron shield disposed between the near detector and the far detector, and a neutron scattering insert disposed inside the housing between the source and the near detector. The scattering insert consists of a material selected from the group of aluminum, beryllium, graphite, silicon, potassium, magnesium, lead and sulfur. In a preferred embodiment, the scattering insert consists of aluminum.

Abstract: A method for determining the permeability of earth formations penetrated by a wellbore from acoustic signals measured by an acoustic wellbore logging instrument. The method includes separating components from the measured acoustic signals which represent Stoneley waves propagating through the earth formations. Signals representing Stoneley waves propagating through the same earth formations are synthesized. The separated acoustic signal components and the synthesized Stoneley wave signals are compared. The permeability is determined from differences between the synthesized Stoneley wave signals and the separated acoustic signal components. In a preferred embodiment, the step of calculating the permeability includes inversion processing a wave center frequency shift and a wave travel time delay with respect to the permeability of the earth formations.

Abstract: A method of measuring the conductivity of earth formations penetrated by a wellbore. The method comprises selectively passing an alternating current through transmitter coils inserted into the wellbore. Each of the transmitter coils has a magnetic moment direction different from the magnetic moment direction of the other ones of the transmitter coils. The alternating current includes a first and a second frequency. The amplitude at the first frequency has a predetermined relationship to the amplitude at the second frequency. The relationship corresponds to the first and the second frequencies. The method includes selectively receiving voltages induced in a receiver coil having a sensitive direction substantially parallel to the axis of the corresponding transmitter coil through which the alternating current is passed.

Abstract: A method for correcting response of an induction logging instrument for inclination of earth formations with respect to an axis of the instrument. The instrument has a transmitter and a plurality of receivers at spaced apart locations. The method includes calculating expected receiver responses of simulated media having different conductivities. The calculations are performed for a plurality of different inclinations. The calculations are also performed for media having a plurality of different conductivity contrasts. 2-dimensional filters corresponding to a charge effect portion of each of the expected responses are calculated. 2-dimensional filters corresponding to a volumetric effect portion of each of the expected responses are calculated. An angle of inclination of the earth formations with respect to the instrument is determined. An approximate conductivity contrast of the earth formations is determined.

Abstract: An apparatus and method for evaluating formation damage proximate to the surface of a rock. The invention is applicable to surface tests and to tests downhole in a borehole. A first hollow probe sealingly contacts the rock surface to define a first surface area, and the pressure within the hollow probe is decreased to monitor resulting pressure changes. A second hollow probe contacts the rock surface to define a second surface area having a different size than the first surface area, and the pressure within the hollow second probe is decreased to monitor resulting pressure changes. Differences in the observed pressure changes can be analyzed to evaluate formation damage to the rock surface and near surface. In particular, the thickness of formation damage, and permeability losses caused by such damage, can be assessed. Alternatively, fluid pressure can be injected into the first and second volumes to evaluate the subsequent pressure reduction.

Abstract: A method of determining the number of exponential decay modes in spin echo amplitude signals from a nuclear magnetic resonance well logging instrument. The method includes dividing the time interval between initiation and termination of measurement of the spin echo amplitude signals into 2r-1 equal length segments, where r is a positive integer. Integrals of the spin echo amplitude signals with respect to time in each of the segments are calculated. Best fit functions are calculated for the spin echo amplitude signals, and integrals with respect to time of apparent amplitudes of the best fit functions at each time corresponding to a time at which the spin echo amplitude signals were generated. The integrals of the spin echo amplitude signals and the integrals of the apparent amplitudes from each segment are arranged into symmetric matrices each having dimensions r.times.r. A norm and a standard deviation of the matrix of the spin echo amplitude integrals is calculated.

Abstract: Wide-angle reflections that have been overcorrected using a simple two-term hyperbolic moveout correction are adjusted by application of a bi-quadratic term. The biquadratic term is derived by scanning the overcorrected reflections for residual velocity. The residual velocity is used to calculate an adjustment as a linear function of the first power of the travel time to each receiver versus the fourth power of the corresponding receiver offset.

Abstract: A high-order, polynomial regression curve is fitted to a global set of first-arrival pick 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 polynomial is applied to the pick times to provide pick time distances with the vertical velocity gradient removed. The known source coordinates, the nominal detector coordinates and the pick time distances are combined to provide a quadratic surface to provide a common data block containing the coefficients for modeling the lateral velocity gradient. Using the so-determined coefficients, the imperfectly-known detector positions are iteratively updated using the Helmert blocking technique.

Abstract: A method of compressing digital signals for transmission and/or storage. The method includes lossy compressing the digital signal to generate a lossy compressed signal. The compressed signal is decompressed locally to generate a local lossy decompressed signal. An error signal is calculated as the difference between the original digital signal and the local lossy decompressed signal. The power in the original digital signal and in the error signal is determined. A minimum resolution for quantizing the error signal is determined from a ratio of the power of the original signal with respect to power of the error signal. The error signals is lossy compressed by quantizing to at least the minimum resolution. Both the compressed digital signal and the compressed error signal are transmitted and/or stored. The lossy compressed error signal and the lossy compressed signal are recovered from storage or transmission.

Abstract: A nuclear magnetic resonance sensing apparatus including a magnet for inducing a static magnetic field in materials to be analyzed, the magnetic field having uniform field strength around, being substantially rotationally symmetric and perpendicular to a longitudinal axis of the magnet. The apparatus includes means for generating a radio frequency magnetic field in the materials to be analyzed. The radio frequency magnetic field is substantially rotationally symmetric about the longitudinal axis and is parallel to the longitudinal axis within a sensitive volume containing the materials to be analyzed. The apparatus includes means for receiving a nuclear magnetic resonance signal from the sensitive volume. In a preferred embodiment, the means for generating and means for receiving include an antenna coil wound so that turns of the coil lie in planes perpendicular to the longitudinal axis of the magnet.

Abstract: An apparatus for generating a large perforation in a target such as a wellbore casing. A liner is positioned within a charge case lowered into a well. An explosive material is initiated to collapse the liner to form a material penetrating jet. A spoiler is positioned proximate to the liner to defocus the liner collapse. The spoiler forms a hollow center in the material penetrating jet and concentrates the energy of the jet into a large annular ring for penetrating the target. The spoiler can comprise a passive spoiler which blocks the full collapse of the liner, or can comprise an active spoiler incorporating a high explosive or an elastic material for counteracting the liner collapse. The spoilers can be spherical, cylindrical, tapered, or another shape to modify the configuration and performance of the material penetrating jet, and a spacer can retain a spoiler in a selected orientation relative to the liner.

Abstract: A method of generating an automatic, three-dimensional, locally-unstructured, hybrid grid for geological formations with a sloping fault. The grid generation system replaces the portion of an existing finite-difference grid around the sloping fault with a finite-element grid made of triangular prisms and tetrahedrons. The process comprises decomposing the part of the reservoir around the sloping fault into topologically and geometrically simple volume, face and line components, generating a wire-frame construction of the domain by discretization of the line components, calculating the exact crossings of horizons with the fault, generating a finite-element grid for the face components using an automatic triangulation process, generating a finite-element grid for the volume elements using an automatic tetrahedronization process and assembling the finite-element grid for all volume elements and the finite-difference grid to create a locally-unstructured hybrid grid with enhanced detail around the sloping fault.

Abstract: A method of determining the acoustic propagation velocities of earth formations using signals generated by an acoustic array well logging instrument. The method includes generating a model of the acoustic velocities including a value of velocity for each propagation mode for which the velocity is to be determined Acoustic waveforms are synthesized for a plurality of receiver locations on the acoustic logging instrument by using the values of the acoustic velocities in the model. A difference is determined between the synthesized waveforms and measured waveforms generated by acoustic energy detected at corresponding receiver locations on the acoustic logging instrument. The model is adjusted and the waveforms are resynthesized until the difference is determined to be at a minimum. The step of adjusting the model is performed by very fast simulated annealing.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A system for evaluating multiphase flow of a fluid downhole in a borehole. Dielectric permittivity electrodes generate a capacitance output signal through the fluid, and conductivity electrodes generate a conductivity output signal through the fluid. The electrodes are powered with an AC generator operating at the same or different frequencies. The capacitance and conductivity output signals can be alternately generated by operating a controller, and such signals can be combined with a multiplexer engaged with the controller. The signal can be processed downhole or can be transmitted to a receiver positioned at the well surface for processing and interpretation of the multiphase data.

Abstract: A method for using geometrical data to determine characteristics of a wellbore penetrating a subterranean formation is disclosed. The method involves converting data obtained from acoustic well logging into cartesian coordinates and solving a general quadratic equation by a least squares fit to an elliptical or circular model. More specific information, such as tensor strain and formation compaction along the wellbore may then be obtained from the geometrical data.