Abstract: A workstation computer system, and its associated method and program storage device, stores a novel software package known as "Variance Cube". The computer system is responsive to a plurality of seismic signals propagating through a cubic volume of an earth formation for generating a cube, representing said cubic volume of earth, where the cube includes a plurality of seismic data samples and where each seismic data sample has a corresponding "variance value" assigned thereto. The computer system also generates one or more maps, such as a time slice map, representing one or more slices through the cube. Each map displays and is used to determine certain geologic features which exist along the corresponding slice through the cube, each map including a plurality of the variance values representing the geologic features, each such variance value being defined as the degree to which an amplitude of each seismic data sample in the cube at a particular reflection time "t" varies about an average amplitude.

Abstract: An anti-noise component for a flat cable including a flat O-like ferrite core having a slit-like hole through which a flat cable is passed, and an openable and closeable case which covers the ferrite core while the slit-like hole is exposed through the case. Further, the case integrally has a coupling portion including a pawl for fixation to an apparatus on which the component is to be mounted.

Abstract: A method for analyzing a target seismic trace generally comprises selecting other traces in source-receiver space not including traces from the same shot record that contains the target trace, and comparing the selected traces to the target trace. The method generally includes setting a distance value indicative of the number of shot gathers to be considered in conjunction with analyzing a target trace, specifying which traces from a plurality of shot records to compare to the target trace based on the distance value, calculating a first amplitude value associated with the amplitude of the target trace, calculating a second amplitude value associated with the amplitudes of the specified comparison traces, and comparing the first amplitude value to the second amplitude value. The comparison and target traces can be analyzed in various windows of time. The target trace is modified in a suitable manner if it is found to contain noise.

Abstract: A method for detection of a disturbance in a waveguide comprising transmitting a wavefield having symmetric and antisymmetric components from a horizontally and/or vertically polarized source and/or pressure source disposed symmetrically with respect to the longitudinal central axis of the waveguide at one end of the waveguide, recording the horizontal and/or vertical component or a pressure of the wavefield with a vertical array of receivers disposed at the opposite end of the waveguide, separating the wavenumber transform of the wavefield into the symmetric and antisymmetric components, integrating the symmetric and antisymmetric components over a broad frequency range, and comparing the magnitude of the symmetric components and the antisymmetric components to an expected magnitude for the symmetric components and the antisymmetric components for a waveguide of uniform thickness and properties thereby determining whether or not a disturbance is present inside the waveguide.

Abstract: The charting method consists in realising a recordings acquisition, constituting on the basis of the recorded seismic traces, a 3D seismic block (X, Y, T) sampled in elementary cells (C.sub.ijk), such that each elementary cell contains a sample (k) of a central seismic trace (TR.sub.ij), calculating for each elementary cell (C.sub.ijk) of the seismic block, the energy thereof, and fixing an energy threshold beyond which the presence Tk of anomaly zones is considered probable, selecting cells of the block which have energy equal or superior to the said threshold, coding the selected cells, such that all the cells belonging to a same contiguously selected cell set have the same code and the selected cells belonging to distinct contiguously selected cell sets have different codes, and effecting an XY projection of the coded cell block.

Abstract: The present invention provides a system, apparatus and method for transmitting logging data from a primary location to a remote location in near real time. The logs can be viewed almost simultaneously at the primary and remote locations, as data is being acquired.

Abstract: A method of determining electric resistivity of an earth formation (1) surrounding a wellbore filled with a wellbore fluid, is provided, which method comprises: operating a resistivity logging tool (2) in the wellbore so as to provide a plurality of resistivity logs (FLG.sub.1, . . . , n) (3) of the earth formation (1) for different radial intervals (1, . . . , n) relative to the wellbore; for each radial interval (k), selecting a modelled resistivity profile (Rmod.sub.k) (4); inputting the modelled resistivity profiles (Rmod.sub.1, . . . , n) (4) to a logging tool simulator (6) so as to provide for each radial interval (k) a modelled resistivity log (MLG.sub.k) (7) having a depth of investigation corresponding to the radial interval (k); for each radial interval (k) updating the modelled resistivity profile (Rmod.sub.k) (7) in dependence of an observed deviation of the resistivity log (FLG.sub.k) (3) from the modelled resistivity log (MLG.sub.

Abstract: In preferred embodiments described herein, a transducer head is affixed to the lower end of a wireline borne scanner sub for rotation thereby. The transducer head includes a pair of transducers which may be adjusted radially inward or outward with respect to the head so that optimum standoff may be achieved without the need for numerous transducer heads of various sizes. In a described exemplary embodiment, the transducers are adjusted by means of an indexing system which permits fine control over the amount of adjustment for the transducers.

Abstract: A system and method to determine an in-situ stress field based on borehole acoustic monopole and cross-dipole measurements. A radially polarized monopole shear-wave is generated in a borehole. It is then determined whether the shear-wave has split into two shear-waves. If it has, the difference in velocities between the two split shear-waves is used to determine the stress induced anisotropy around and near the borehole. The difference in velocities of cross-dipole shear-waves and the direction of the fast shear-wave are measured and used to determine the magnitude of the maximum shear stress and the maximum stress orientation of the geologic formation. Furthermore, a method of determining the stress-velocity coupling coefficients from laboratory measurements as well as through field measurement calibration is disclosed. The effect of borehole pressure on the field measurement calibration method of determining the stress-velocity coupling coefficients is taken into account.

Abstract: A velocity independent method of predicting surface-related multiples in any gather of seismic data traces. In one embodiment, the method comprises the steps of regularizing said gather of seismic data traces; performing a double Fourier transformation to transform said seismic data traces from the x-t domain to the k.sub.x -.omega. domain; decomposing said transformed seismic data traces into uncoupled amplitude and phase spectra; and obtaining an estimate of said surface-related multiples by scaling said amplitude spectrum by one-half the value of the reflection coefficient for the first reflection below the earth's surface and by doubling said phase spectrum. The estimated multiples may then be used for automated velocity determination or for multiple attenuation in the original data.

Abstract: A method for determining migration before summation including recording seismic reflection traces, for constituting a collection of traces to be migrated before summation and without weight correction. The traces being classified according to a given criterion and using a velocity model. The method including determining, for each point of interest M in a domain (X, Z), at least one line of slope determined on the basis of a line of slope map, in determining the specular rays associated with one point M and for the line of slope, and in computing the time and amplitude characteristics of each of the specular rays for deducing therefrom the reflection factor in each point M.

Abstract: A computer implemented method and apparatus for discovering hydrocarbon bearing formations yields a direct indication of hydrocarbon resulting from analyzing seismic amplitude data. The method uses an algorithm for determining a seismic attribute known as delta amplitude dip (DAD) in which each sample point of each seismic trace in a survey is analyzed to determine a planar dip associated with the reflection point and a normalized delta amplitude in the direction of dip. Displaying the DAD values in time slice or horizon slice format provides a direct indicator of hydrocarbons. The inventive method automatically analyzes each digitized data point in the survey by cross correlating the traces reflected from a three-by-three array of reflection points. This method involves cross correlation of eight traces that are reflected from the perimeter of the three-by-three array of reflection points with the single trace reflected from the central point in the array.

Abstract: The present invention provides a system for drilling boreholes having a downhole subassembly which contains an acoustic measurement-while-drilling system. The acoustic system contains an acoustic transmitter and receiver for determining the acoustic velocity through the formations surrounding the borehole ad an acoustic transmitter and a set of receivers for determining the bed boundaries surrounding the borehole formation utilizing the acoustic velocities measured by the system. The downhole subassembly also contains a computing system which performs computations downhole and transmits certain answers uphole during the drilling operations. The bed boundary information is utilized to drill the wellbore along a desired wellbore path. The downhole computing system correlates the acoustic sensor measurements with other measurement-while-drilling measurements and transmits selected correlated information uphole.

Abstract: A method and apparatus for detecting rock movement. The first step involves using at least one electromagnetic induction coil as a sensor. The second step involves monitoring changes in induced electromotive force in the at least one electromagnetic induction coil over a selected time interval. This new approach is based upon changes in magnetic permeability as a result of rock movement in accordance with Faraday's law of electromagnetic induction. When a plurality of these new sensors are used the speed of the rock movement may also be determined.

Abstract: A method for making seismic while drilling (SWD) measurements by determining and analyzing the reference signal downhole near the drill bit and sending a limited quantity of information to the surface by measurement-while-drilling (MWD) telemetry. In one embodiment, a library of anticipated drill bit wavelets is stored in memory downhole and in memory at the surface. The best matching wavelet is identified by the processor downhole and then a code identifying the wavelet and a scaling factor is sent to the surface. At the surface, the best matching wavelet is retrieved based on the code received and then a reconstructed signal is created using the retrieved wavelet and the scaling factor. In another embodiment, key characteristics of the signal such as central frequency, frequency band, etc., are calculated downhole and transmitted to the surface. These key characteristics are then used to reconstruct the reference signal which is then used for correlation of surface detected signals.

Abstract: A seismic prospecting method allowing positioning in space of geologic events in the neighborhood of a well and calculation of the dip and the direction of dip. Seismic waves are transmitted into the formation, and three-axis seismic sensors placed in the well and coupled with the formation surrounding the well receive seismic data corresponding respectively to components along the three axes of seismic waves reflected by discontinuities in the formation in response to the transmitted seismic waves. Orientation data defining orientation in space of the three-axis seismic sensors is assigned to the seismic data.

Abstract: A two-step process for clearing unexploded ordnance ("UXO") from the ground. First a high power electromagnetic transmitter sweeps the ground area to be decommissioned. Secondly a lower-power time-domain electromagnetic transmitter or metal detector sweeps the same area to locate UXO. The high power transmitter employs a waveform of having the same frequency and pulse duration as that of the metal detector but does so with at least twice the power, Firstly, when the higher power waveform is applied to the ground, UXO which does not trigger and detonate or "function" is proved as non-functioning at lower detection power. Subsequently, the ground area can then be safely scanned by human personnel with impunity, applying the more accurate, lower power metal detector. The detected locations of unexploded ordnance are recorded for subsequent manual removal.

Abstract: A seismic handling device for safely transporting, deploying, and retrieving a seismic unit on a sea vessel is disclosed. The seismic handling device comprises a plurality of vertical structural members extending from the vessel. A plurality of horizontal structural members are connected to the vertical structural members. A delivery system is securely attached to the horizontal structural members. The delivery system positions the seismic unit into the sea, tows the seismic unit during a survey and retrieves the seismic unit from the sea.

Abstract: The invention relates to a two-phase method of transmitting, to a central station (CS), seismic signals received by seismic receivers (R) and picked up by collecting units (A) disposed in the field. In the first phase, a compression is applied to each seismic trace, the ratio of which is adapted to the duration of a transmission window placed in the time intervals between successive seismic transmission-reception cycles, as well as to the rate of the transmission route used. The compressed trace as a whole is thus transmitted, allowing an operator at central station (CS) to check qualitatively that recording took place correctly in each collecting unit (A) even though he does not have the exact trace available.

Abstract: For various reasons it may be desirable to change the way a sonde is programmed to behave and respond to the data it receives and operates on, and at present each time this must be done it has been necessary to lift the sonde out of the borehole and then disassemble it to permit the removal of the old ROM and its replacement with a new ROM storing the new program. The operability and efficiency of such an arrangement is poor. To deal with this, the present invention proposes that the sonde also includes: signal processing means for processing a sampled detection signal according to a predetermined signal processing program; first memory means for storing that signal processing program; and second memory means storing a writing program for writing the signal processing program in the first memory means according to a command from the ground surface processing apparatus.