Abstract: A method for modeling fracture zones in the sidewall of a borehole and for estimating the hydraulic conductivity thereof. The method first separates Stoneley wavefields into a directly-transmitted wavefield and a one-way (i.e. downgoing) reflected wavefield from which the depth configuration may be determined. The separated wavefields are corrected for the effects of borehole irregularity due to such effects as washouts and the like by numerically modeling Stoneley wave propagation using caliper and slowness measurements. The hydraulic conductivity is estimated from parameters derived from synthetic and measured Stoneley-wave data across the fracture zone in combination with measurements of the borehole radius.

Abstract: Sparsely spatially-sampled seismic time-scale trace gathers may be aliased for certain spatial and temporal frequencies. Aliasing may be avoided by application of a spatial interpolation scheme that uses the phase difference between the f-k phase spectra of the odd and the even traces to generate an interpolation operator in the f-k domain. The operator is multiplied point-by-point with the f-k transform of the original recorded trace gather. The resulting complex product is inverse transformed to the t-x domain whereupon the interpolated traces are interleaved between the original recorded traces to unwrap the aliased events.

Abstract: A method for using a compressional-wave source to produce converted shear waves which are subjected to Alford 4-component rotation to align the observation coordinates with the natural coordinates of the principal anisotropic axes of a birefringent formation. The static time shift between the fast and the slow shear wavefields due to shear-wave splitting is determined so that they can be synchronized thereby to isotropize the birefringent formation. From those data, fracture-plane orientation can be determined. Based on those data, the direction of a deviated bore hole is aligned perpendicular to the fracture plane strike. For a deep-seated target formation, shallower layers are isotropized prior to rotation and synchronization of the converted shear wavefields originating from that deeper formation.

Abstract: A variable-gap, distributed-capacitance sensor provides an output signal that is a function of its instantaneous elongation. The sensor is integrally associated with a seismic isolator section for measuring the instantaneous stretch thereof.

Abstract: In the presence of an anisotropic near-surface earth layer, orthogonally oriented microspreads are provided from which shear-wave velocity vectors V.sub.si.theta. and V.sub.s.theta. may be determined. The respective velocities are calculated from measurements of the direct path first arrivals and of the velocity of the boundary waves propagating along the upper boundary of the near surface layer. The ratio of the near-surface shear-wave velocity vectors is used to scale the static time corrections attributable to seismic data received by shear wave sensors whose axes of responsivity coincide with the orientation of the microspreads.

Abstract: A fluidic actuator includes dual-element, differential area pistons consisting of a power piston and an extender piston that are mounted in a double-chamber cylinder. A spring-loaded throttling plunger is slidingly mounted in a longitudinal bore in the power piston to meter the flow of pressurized fluid against to the extender piston as a function of the incremental stroke length of the extender piston.

Abstract: A method for measuring the velocity of shear waves in a formation beneath a body of water. The shear wave velocity is derived from the parameters of water density, water-bottom reflection coefficient, formation compressional wave, velocity and the propagation velocity of a submarine ground-roll wave front.

Abstract: The amplitude spectrum is generated within a selected time window of a seismic time scale recording. The rate of change, Q, of the natural logarithm of the signal amplitude is measured with respect to frequency. A Q-derived static time shift is computed and applied to the selected seismic time scale trace to correct the raw seismic times for dispersion-induced time distortion. Amplitude-correction and phase-correction filters are applied to the static-corrected trace to provide a new time scale trace corrected for velocity dispersion which is processed to provide a physical model of the subsurface of the earth.

Abstract: The signal-to-noise ratio of televiewer signals from a rotary sidewall acoustic-beam scanner is improved by replacing the volume of borehole drill fluid that lies in the path of the acoustic beam with a solid medium characterized by a lower coefficient of attenuation than that of the drill fluid.

Abstract: As a means for determining the preferred azimuthal alignment of a horizontal borehole, the reflection travel time vectors between an acoustic source and a plurality of equidistant seismic receivers are measured along a plurality of directional wavefield trajectories. The travel time vectors are resolved to measure the angular orientation of the strike of vertical stress patterns. The alignment of the horizontal borehole is directed perpendicularly to strike.

Abstract: A multivariate stochastic simulation application that involves the mapping of a primary variable from a combination for sparse primary data and more densely sampled secondary data. The method is applicable when the relationship between the simulated primary variable and one or more secondary variables is non-linear. The method employs a Bayesian updating rule to build a local posterior distribution for the primary variable at each simulated location. The posterior distribution is the product of a Gaussian kernel function obtained by simple kriging of the primary variable and a secondary probability function obtained directly from a scatter diagram between primary and secondary variables.

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 vegetation harvesting/clearing device consists of an assembly including a pair of hinged jaws and an open noose of cable, all of which is mounted on a load-lifting device of a prime mover such as a farm tractor. The open jaws are deployed to cause a patch of vegetation to be enclosed by the open noose. The jaws are closed around the vegetation, whereupon the noose is tightened to garrote the vegetation in a swath. The load lifting device raises the closed jaws to uproot the vegetation and to remove the swath of uprooted material to a disposal site where the swath is deposited.

Abstract: A method for increasing the signal-to-coherent-noise ratio of seismic signals propagating along multi-azimuthal trajectories by abating Rayleigh wave contamination. A plurality of seismic receivers surround a nest of vibrators separated by a first uniform incremental spacing whereupon the vibrators emit chirp signals. The chirp signals are received by the seismic sensors, the received signals are stacked, auto-correlated, integrated and the integrated signal level is tabulated as a function of vibrator separation. The first vibrator separation is repeatedly uniformly expanded by a selected increment and the steps of emitting, receiving, stacking, auto-correlating and tabulating are repeated after each incremental separation. The separation corresponding to the minimal integrated signal level is selected.

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: 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: 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: 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: 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: 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.