Abstract: An approximate method for imaging seismic data that originates from steeply dipping or overturned strata. The method provides a viable alternate approach to the generalized f-k migration that does not rely explicitly on some form of perturbation series expansion and thus avoids the steep-dip instability that is present in previously-known methods. This method is particularly useful in the presence of a moderate lateral velocity gradient, something that prior-art methods have trouble accommodating. An advantageous feature of the disclosed method is that the migration/imaging operators are composed of simple numerical coefficients.

Abstract: A method for determining density of a formation. The method includes irradiating the formation with gamma rays having energy consistent with Compton scattering. Gamma rays are measured at axially spaced apart locations. Two of the axially spaced apart locations are at an equal distance and in opposite directions relative to the source of gamma rays. The distance is smaller than the spacing of another one of the spaced apart locations. An apparent density for each spaced apart location is determined from the counts. Differences are calculated in apparent density between each one of the spaced apart locations, and a correction factor is determined for apparent density at each spaced apart location, thereby determining the density of the earth formation. In a preferred embodiment, determining correction factors is performed by a neural network using the differences in apparent density as an input vector.

Abstract: A system for determining formation gas saturation in a cased wellbore which includes a neutron logging tool having a source, a first neutron detector offset towards the wellbore primarily sensitive to the wellbore and a second detector spaced further from the source and offset towards the formation, so that the second detector is sensitive primarily to liquid-filled porosity in the formation. The detectors are encased in a neutron moderator. The system includes a method of determining gas saturation in the formation by measuring count rates at the detectors, generating a wellbore gas saturation from the first detector counting rate, generating a ratio of counting rates of the second and first detectors to generate a value of liquid-filled porosity in the formation, and calculating a gas saturation in the formation by combining the liquid-filled porosity with a measurement of total porosity.

Abstract: Pressure and velocity seismic signals are combined, the combined signal is transformed into the frequency domain and multiplied by the inverse Backus operator or the combined signal is convolved with the inverse Backus operator, and an optimization algorithm is utilized to solve for water bottom reflectivity. Pressure and velocity seismic signals are combined, and the combined signal is multiplied by the inverse Backus operator containing the water bottom reflectivity to eliminate first order peg leg multiples.

Abstract: The present invention is a system for severing pipe. The system includes an explosively actuated pipe cutter, a pressure actuated initiator, and a means for suspending the cutter and the initiator inside the pipe and pressure sealing the interior of the pipe.In a particular embodiment of the invention, the initiator includes a time delay to enable reduction in pressure applied to the interior of the pipe for actuating the initiator.

Abstract: This invention provides a method for performing three dimensional seismic surveys. In one configuration, receiver lines containing equally spaced receiver stations run in one direction while the source station lines run diagonal to the receiver station lines. The receiver stations and/or the source stations are offset to obtain a desired spatial sampling (number of bins) or multiplicity of the common mid points. In an altemate configuration, the receiver line spacing is offset by a fraction of the source station spacing and/or the source line spacing is offset by a fraction of the receiver station spacing to obtain the desired spatial sampling. These configurations provide higher spatial sampling (smaller bins) compared to the conventional geometries. The smaller bins may be combined to obtain folds (multiplicity) which is sufficient to provide desired seismic imaging while preserving the benefits provided by the higher spatial sampling by the method of the present invention.

Abstract: The present invention is a differential pressure fluid density instrument comprising a housing having a plurality of ports positioned at spaced-apart locations along the housing, a differential pressure transducer, and a valve adapted to selectively connect the transducer across two predetermined one of the plurality of ports. The valve may comprise a three-way solenoid actuated valve. Fluid expansion wells are each connected at one end to a port and prevent wellbore fluids from reaching the differential pressure transducer. The housing includes an inner chamber filled with liquid which may be silicon oil. The chamber includes a standpipe which extends from near the bottom of the chamber, where it is in communication with a lower port, to the top of the chamber. Communication between the chamber and wellbore through the standpipe enables the housing and components disposed within the chamber to be constructed without the need to withstand high differential pressures.

Abstract: A method for measuring the principal axis of fracture-induced formation anisotropy. Amplitude vectors are measured from CMP gathers oriented along in-line and cross-line wavefield trajectories. The amplitude vectors are resolved with the known orientations of the seismic lines of survey to estimate the azimuth of the anisotropic axis.

Abstract: An efficient method for evaluating static corrections based upon molecular dynamics simulation. This approach combines the global minimization mechanism of simulated annealing and the deterministic approach of molecular dynamics simulation and finds the surface-consistent source and receiver static corrections by minimizing the objective function. The objective function is a measure of the reflection coherency of the whole data set.

Abstract: The invention is a method of synchronizing a digital telemetry receiver to a digital telemetry transmitter. The method includes the steps of initializing the sampling period of the receiver, measuring the detection time of each signal event detected by the receiver relative to a time window based on the sampling period, accumulating statistics representing the detection times of each of the events, and calculating a refined sampling period based on a linear regression fit of the actual detection time of each event.

Abstract: An apparatus for communicating signals from a well logging tool to a recording unit is disclosed. The logging tool includes a transmitter comprising a source of digital bits representing measurements made by the tool, an encoder connected to the source of digital bits for transforming groups of the digital bits into multivalued symbols, a first in-phase filter and a first quadrature filter connected to the encoder so that first coordinates of the symbols are filtered in the in-phase filter, second coordinates of the symbols are filtered in the quadrature filter, the filters having responses forming a Hilbert transform pair, a digital subtractor connected to the first filters for calculating a difference between outputs of the filters, and a digital-to-analog converter connected to the output of the subtractor for generating signals to be communicated to the recording unit over a communication channel.

Abstract: Disclosed is a method for processing geophysical data that have been gathered over irregular topography. According to the method, a datum is established that lies above the highest topographic peak. The data are time-shifted from the surface to the datum using a replacement velocity that is an extrapolation of the underlying formation velocity. The wavefields beneath the surface are forwardly modeled using a modeling velocity substantially equal to zero. Between the surface and the datum, the wavefields are upwardly modeled using the replacement velocity.

Abstract: A method for concurrently gathering acoustic and resistivity data for mapping the texture of the sidewall of a borehole using a single imaging tool. The data are sampled, formatted and merged to provide a single composite image of the borehole sidewall.

Abstract: One or more slave acoustic transponders are secured to selected parts of a seismic bottom cable whose location is imperfectly known. A master transponder broadcasts an interrogation pulse from each of a number of different, known locations distributed along a line of survey. In response to an interrogation pulse, a slave transponder emits an encoded signal that is received by the master transponder. The acoustic flight time between each pulse broadcast and encoded-signal reception constitutes a range measurement to the participating slave transponder. Resolving a gather of several range measurement from different known broadcast locations, focussed on an identifiable transponder, defines the transponder location.

Abstract: The present invention is a well logging cable including first conductor elements, each of the first elements consisting of a steel wire surrounded by copper strands and covered in an electrically insulating material, and at least one second conductor element including at least one optical fiber enclosed in a metal tube, copper strands surrounding the tube and the strands covered by the electrically insulating material. The first elements and the at least one second element are arranged in a central bundle. The second conductor element is positioned within the bundle so as to be helically wound around a central axis of the bundle. The bundle is surrounded by armor wires helically wound externally to the bundle.

Abstract: A method for spectral noise abatement from seismic data. The data are decomposed into organizational components from which a noise component can be resolved by well-known iterative methods. A statistic is calculated by comparing the measured spectral content of the data with a model spectrum. The seismic data are scaled in proportion to the ratio between the model spectrum and the measured spectrum, following which the processed signal traces are displayed as representative of a cross section of the earth.

Abstract: The invention is a method of determining the thickness of a casing in a wellbore penetrating an earth formation using group delay determined casing resonance extracted from processed reflection signals from an acoustic pulse-echo imaging tool. A first Fourier transform coefficient series is calculated from the digitized reflection signal. Individual samples of the reflection signal are multiplied by their sample index values to obtain a modified digitized data string. A second Fourier transform coefficient series is calculated from the modified digitized data. The complex group delay function is calculated directly from the first and second Fourier coefficient series.

Abstract: The present invention is a system for analyzing the energy levels of radiation detected by a radiation detector having a multichannel pulse height analyzer. The radiation detector generates signals representative of the energy level of the detected radiation, and the analyzer increments a particular channel dependent on the signal from the detector. The channel incremented by the analyzer is in response to an empirical relationship of the particular channel with respect to energy level. The empirical relationship is determined so that energy spectral peaks occurring over substantially the entire energy detection range of the detector have peak widths spanning substantially equal numbers of analyzer channels. In one embodiment of the invention, the detector is a scintillation counter responsive to gamma ray radiation. In one embodiment of the invention, the empirical relationship is approximated by an ordered expression comprising a third order polynomial function.

Abstract: An apparatus for perforating an earth formation from a borehole having a housing, a detonator assembly, explosive material for producing the implosion forces and a metal liner of implosive geometry. The detonator assembly includes a predetermined pattern of precision electronic detonators based on exploding foil initiator, exploding bridge wire, spark gap or laser technology to simultaneously produce multiple initiation points of the explosive material for enhancing the implosion forces.

Abstract: The relative amplitudes of seismic reflection data contains very useful information about the subsurface earth formations. Surface and subsurface-consistent amplitude processing identifies and corrects for the variability introduced by instrumentation and surface distortions. Dynamic amplitude decomposition, the subject of this disclosure, identifies and compensates for reflection amplitude fading due to subsurface transmission absorption media.