Abstract: Simultaneous sources are separated with a deblending method wherein the fullband data deblended on a source-by-source basis. The fullband data is first decomposed into multiple subbands, and then a non-equispaced subband Radon transform is used to transform the decomposed data into the Radon domain. The deblending process is solved subband by subband by minimising a nonlinear objective function. The solution of the nonlinear objective function is found using a multi-step procedure.

Abstract: A method for electromagnetic geophysical surveying according to one aspect of the invention includes disposing a plurality of electromagnetic receivers in a selected pattern above an area of the Earth's subsurface to be evaluated. An electromagnetic source is repeatedly actuated proximate the electromagnetic receivers. Signals generated by the receivers, indexed in time with respect to each actuation of the at least one electromagnetic energy source, are recorded. The recorded signals are processed to generate an image corresponding to at least one point in the subsurface. The processing includes stacking recordings from each receiver for a plurality of actuations of the sources and beam steering a response of the receivers such that the at least one point is equivalent to a focal point of a response of the plurality of receivers.

Abstract: Seismic data representing the propagation of seismic energy through a geologic volume of interest is processed. The seismic energy propagates through the geologic volume of interest from one or more source locations at or near the geologic volume of interest to one or more detector locations at or near the geologic volume of interest. In processing the seismic data, the seismic energy is modeled as beams (e.g., Gaussian beams). The processing performed (i) corrects for misalignment of the one or more source locations and/or the one or more detector locations with a regular, predetermined mesh, and (ii) steers the seismic data based on the modeled beams.

Abstract: A method for seismic surveying includes disposing a plurality of seismic sensors in a selected pattern above an area of the Earth's subsurface to be evaluated. A seismic energy source is repeatedly actuated proximate the seismic sensors. Signals generated by the seismic sensors, indexed in time with respect to each actuation of the seismic energy source are recorded. The recorded signals are processed to generate an image corresponding to at least one point in the subsurface. The processing includes stacking recordings from each sensor for a plurality of actuations of the source and beam steering a response of the seismic sensors such that the at least one point is equivalent to a focal point of a response of the plurality of sensors.

Abstract: A method for passive seismic surveying includes deploying seismic sensors in a plurality of spatially distributed wellbores disposed above a volume of subsurface formations to be evaluated. The sensors in each wellbore form a line of sensors. Each sensor generate optical or electrical signals in response to seismic amplitude. The seismic signals from each sensor are recorded for a selected period of time. The response of the seismic sensor recordings is beam steered to at least one of a selected point and a selected volume in the subsurface. At least one microseismic event is identified in the beam steered response.

Abstract: A method for designing a sound waveguide surface is described. The method includes the steps of forming a parametric model of the sound waveguide surface where the parametric model has at least one input parameter and then simulating a sound field that is formed by the sound waveguide surface. A frequency dependent spatial distribution measure is then determined for the sound field associated with the sound waveguide surface and the at least one input parameter is varied to change the sound waveguide surface to adjust the value of the frequency dependent spatial distribution measure.

Abstract: A method for characterizing fluid pumping effects on a subsurface formation includes (a) during pumping of fluid into the subsurface formation, detecting passive seismic signals related to fractures created in the subsurface formation. (b) A place of origin of the passive seismic signals is determined. (c) A seismic energy source is actuated for a plurality of actuations and an output thereof is beam steered toward the place of origin. (d) At least one acoustic property is determined for the place of origin using signals detected as a result of the plurality of actuations. The detected signals are beam steered toward the place of origin and are stacked over the plurality of actuations. (a), (b), (c) and (d) are repeated until the pumping is completed.

Abstract: Multiple twisted or rotated arrays are provided. For example, a memory alloy may allow manufacture of multiple rows of elements on a flat substrate. The memory of the alloy is activated to twist different rows in different ways, such as two adjacent substantially parallel but oppositely rotated arrays. By selecting different apertures along a given twist, different planes are scanned due to the difference in direction of the elements of the aperture. By selecting different apertures on differently rotated arrays, a larger volume may be scanned.

Abstract: The disclosure identifies method and apparatus for seismic exploration which may be used to provide improved positioning of land-based seismic sources in an array. Also described are methods which make use of the improved positioning to allow, in some examples, improved direction or distribution of the energy beam resulting from actuation of the sources. Some methods make use of the described techniques to steer the energy beam; and in some cases at each source or a distribution location, multiple shots will be taken to distribute the beam in multiple orientations relative to the central source point.

Abstract: A system and method is provided that uses signals from a plurality of seismic sensors to define an acoustic lens for subsurface imaging. More specifically signals provided by an array of sensors/geophones may be utilized to form an acoustic lens that can be focused on a subterranean point by properly adjusting the signals recorded at each sensor prior to summation of those signals. To form such an acoustic lens, each of the seismic sensors is moved onto a hypothetical acoustic lens surface (e.g., spherical surface) having a focal point located on the subterranean point of interest in order to calculate a time delay for each signal. Once the signals for each sensor is time-delayed, information in the time-delayed signals, which is received from the point of interest, may be temporally aligned. Accordingly, the time delayed signals may be combined to generate reflection information for the point of interest.

Abstract: Providing a set of seismic sources in a focusing array to enable concentrating seismic energy in a selected target point (k) in an underground formation, by performing a standard seismic survey of the underground formation using a set of impulsive seismic sources and a set of downhole seismic receivers j, and recording the signals uij(t), selecting a position k to be the target point; obtaining from the signals uij(t) the one-way travel times &tgr;ik from a number of sources i to the target point at the location k; and calculating ti=t0−&tgr;ik to obtain the activating times ti at which the impulsive seismic sources i have to be activated, in order to get a focusing array of the seismic sources i of which the seismic waves arrive at the target point k in phase at time t0.

Abstract: A method for performing a seismic survey with even fold. An inline direction and a crossline direction are selected. Seismic signals are generated at a plurality of source locations positioned along one or more source lines. The source locations are substantially equally spaced, and the source lines are substantially parallel to each other. Seismic signals are detected at a plurality of receiver locations positioned along a plurality of receiver paths having longitudinal axes parallel to the inline direction, and substantially equally spaced in each receiver path. Each receiver path is positioned along its axis, and extends in a regular pattern on both sides of the axis. The axes are substantially parallel to each other. A desired fold, F.sub.i, is determined in the inline direction, and a desired fold, F.sub.x, is determined in the crossline direction. A number of receiver channels, NC.sub.i, per receiver path in the inline direction, a spacing, RI.sub.

Abstract: Disclosed is a method for efficiently and accurately determining subsurface velocities for use in migration of seismic data. The method calls for restricting the number of traces considered to those lying upon that portion of the Kirchhoff summation curve wherein the integrand for Kirchhoff migration is smooth. In the preferred embodiment, only a random sample of traces within this aperture are used in the calculations. Improvements in efficiency on the order of a factor of 1000 can be realized with the preferred embodiment.

Abstract: A method and system provide for the sensing of objects under water where the acoustic energy is suitably focused or directed so that reverberation returns are minimized. A vertical source array of adjustable acoustic sources is located in the water body, with each acoustic source producing a separate acoustic pulse or continuous wave controlled by a control device. The control device controls a phase and amplitude of the separate acoustic pulses such that a waveform (combined acoustic pulse) with selective nodes adjustable to a desired depth is emitted. A calibration device is also located at a distance from the source array for calibrating the separate acoustic pulses or continuous wave so that the source array emits a desired waveform. The calibration device includes a checking device for determining whether the emitted waveform conforms to the desired waveform and for calculating a deviation of the emitted waveform from the desired waveform.

Abstract: The present invention provides novel methods for identifying, characterizing and mapping seismic noise as an aid in evaluating and enhancing seismic data. In particular, an array of seismic receivers can be beam steered to sense seismic energy arriving from a plurality of azimuths. A measure of the strength of the seismic energy for each azimuth can be obtained for a plurality of arrival times, velocities and distances from the array. Displays of the azimuthal distribution of the strength of the seismic energy sensed by the areal array can then be produced for identifying and characterizing seismic noise into seismic data.

Abstract: A method for determining the location of steeply dipping subsurfaces includes acquiring seismic reflection data, identifying select data which has characteristics indicating that the acoustic pulses which it represents have been reflected from a substantially horizontal interface and a steeply dipping interface, analyzing the select data to locate the steeply dipping interface and displaying the analyzed data.

Abstract: Method of analyzing the structure of a medium by means of waves reflected by inner interfaces, comprises: (a) generating multiple coverage data represented by traces corresponding to a plurality of source-receiver pairs distributed according to an asymetric polynomial distribution with respect to a predetermined central point with optimal parameters which provide that all reflected events of such traces correspond to the same common reflecting point on a reflecting interface; (b) correcting the recorded traces according to an optimal time delay correction which converts all reflected events to the same phase and which depends on the local parameters of wave propagation velocity Vo at the reference level, and of radius of curvature r.sub.o of the wavefront emitted by a fictitious source located at the common reflecting point and coming to the central point at an angle of entry .beta.

Abstract: A method is disclosed for converting seismic data obtained at known points to synthesized seismic traces obtainable at arbitrarily selected points. Two dimensional seismic data are converted to dense three dimensional data with the aid of a programmed computer to permit generation of arbitrary views of a particular geologic structure as well as a mathematical representation of the structure. The data is used to locate potential drilling and mining locations for drilling oil or other minerals. In order to provide accurate interpolation from the sparse two dimensional data, both apparent and true dip characteristics are obtained for the surveyed structure, and seismic trace data for a desired point are synthesized as a function of the dip of the surveyed structure. The dip characteristics are obtained from partial derivatives of the two dimensional data in specified coordinate directions. A three dimensional surface corresponding to the dip characteristics is obtained by a least squares fitting technique.

Abstract: In a VSP survey, the subsurface coverage of the bounce points of primary reflections is limited to one-half the offset between a borehole and a seismic-source point. The subsurface coverage may be extended by use of selected multiply-reflected wavefield arrivals.

Abstract: A case assembly for vehicular rearview mirrors adapted to support lights for illuminating portions of the vehicle interior, instruments such as directional compasses or the like, and controls such as switches or instrument adjustment units. The case includes one, and preferably two, spaced, removable carrier modules fitted generally flush with the bottom of the mirror case. The carrier modules may include varying combinations of light assemblies for map reading, courtesy or console illumination, switches, and controls for compasses, clocks, electronic or other instruments. A preferred light arrangement provides illumination of areas below and outwardly of the case ends with brighter, targeted lighting areas in the lap areas of persons seated in the front seats of the vehicle.

Abstract: Method and apparatus are disclosed for converting seismic data obtained at known points to synthesized seismic traces obtainable at arbitrarily selected points. Two dimensional seismic data are converted to three dimensional data with the aid of a programmed computer to permit generation of arbitrary views of a particular geologic structure as well as a mathematical representation of the structure. In order to provide accurate interpolation from the known data, both apparent and true dip characteristics are obtained for the surveyed structure, and seismic trace data for a desired point are synthesized as a function of the dip of the surveyed structure. The dip characteristics are obtained from partial derivatives of the two dimensional data in specified coordinate directions. A three dimensional surface corresponding to the dip characteristics is obtained by a least squares fitting technique.

Abstract: A method and apparatus are disclosed for selectively reinforcing an acoustic wave traveling in a first predetermined direction in a body of water while attenuating an acoustic wave traveling in a second opposite direction. The output signals from vertically spaced receivers are appropriately delayed and summed to reinforce a wave traveling in the first direction and attenuate the wave traveling in the opposite direction. The invention is particularly useful for reinforcing desirably detected ascending acoustic waves and attenuating undesirably detected surface reflected descending waves.

Abstract: A logging sonde has directivity control of multiple sources and receivers in linear arrays. Each of the sources produces acoustic pulses which are delayed by a time delay between the sources to direct acoustic energy at an angle such that the resulting acoustic wave strikes a vertical formation orthogonally. The reflections of the acoustic pulses are detected with a linear array of receivers. The acoustic pulse detected by each receiver is delayed by an amount such that the total differential moveout for a reflected directional wave is zero.

Abstract: Arrays of seismic wave sources and seismic wave sensors are towed over an area to be refraction surveyed in such a way that source and sensor geodetic positioning is duplicated during successive source firings. A plurality of traces having these same source/reflection point/sensor geometry are gathered from those produced by each series of successive source firings at the same location and stacked to generate a new trace having improved signal to noise ratio. Positioning is accomplished by uniformly spacing each of the sensors and sources in their respective arrays, the sources being spaced at integer multiples of the spacing of the sensors, and towing both arrays behind the same boat. If irregular or rapidly changing seismic statics are not present, all traces from common reflection points may also be gathered, corrected for normal moveout and stacked to generate a composite trace having enhanced primary reflection returns as well as improved signal to noise ratio.

Abstract: The invention relates to seismic prospecting of the sub-surface.At least two adjacent focuses F and F', at least one reflecting interface H and directions such as (D.sub.1) and (D.sub.2) are selected in the sub-surface. A seismic trace, from which a portion containing the effect due to the reflecting interval is extracted, is made to correspond to each direction and to each focus. The correlation function between the two trace portions relative to two adjacent focuses and the same direction is then determined. The correlation functions obtained are finally summed for the different directions.Application to high resolution seismic prospecting.

Abstract: A method of seismic exploration by which substantially plane or substantially cylindrical seismic energy waves are simulated by combining reflectional signal traces of conventional spherical seismic waves. Seismic sources and receivers are established in sets at positions such that at least one of the sets includes a plurality of positions spaced over an extent of the area being explored having either one or two dimensions which are large relative to a seismic energy wavelength. Seismic energy is imparted into the earth from the sources and signals are generated in response to seismic energy received at the receivers. The generated signals are then combined into a form simulating the reflection response of the earth to seismic energy having a substantially continuous wavefront in either one dimension, simulating a cylindrical seismic energy wave, or two dimensions, simulating a plane seismic wave.

Abstract: This specification discloses a method of seismic exploration and in particular a method of generating and gathering field seismic data. Paths or seismic lines are traversed across the earth or water layers overlying the earth and over subsurface earth formations thereunder, and seismic energy is generated and transmitted into the earth and a portion thereof is reflected from the subsurface formations back toward the surface of the earth where the reflected seismic energy is detected and recorded. In conducting the seismic survey, a long linear array of seismic sources is simultaneously activated to produce a seismic pulse that is focused essentially vertically into the earth, and seismic energy is reflected from subsurface formations thereof and is detected by a long array of seismic detectors and is recorded.

Abstract: Seismic prospecting method for determining the flank dip of subterranean layers with respect to the plane of a seismic profile, comprising sequentially transmitting acoustic waves with different directivity diagrams, recording the corresponding reflected waves, combining, according to a determined law, the transmitted acoustic intensities and, separately, values representative of the intensity of the reflected waves, in each of the directivity diagrams and comparing the results of said separate combinations.

Abstract: Seismic traces synthesizing the response of subsurface formations to a cylindrical or plane wave are obtained for a succession of shotpoint locations along a seismic line of profile. The traces obtained are then wavefront steered and the steered traces and original trace for each shotpoint are summed. Groups of these traces for a line of profile are assembled to form a steered section. A number of these sections are then individually imaged or migrated, and the migrated sections are summed to form a migrated two-dimensional stack of data from cylindrical or plane wave exploration. Reflectors may then be located by finding common tangents.The traces for those shotpoints of the several lines which lie in planes perpendicular to the lines are then assembled and processed in the foregoing manner to obtain three dimension migrated seismic data.

Abstract: A novel array of vertically and horizontally spaced hydrophones is shown which is capable of high ratio of desired signal to noise because of good directional sensitivity when used with any seismic source. Alternatively, a novel directionally sensitive array of vertically and horizontally spaced seismic sources is disclosed for use in seismic surveying with any spread of hydrophones or geophones, again attaining a high ratio of desired signal to noise. A reception pattern (in the first case) and a radiation pattern (in the second place) is produced which essentially eliminates reception or radiation at all frequencies except for waves within a predetermined angle with respect to the array. The sensitivity is essentially constant within such angle for all frequencies and essentially zero outside it.