Abstract: Explicit depth extrapolation operators are constructed with variable operator lengths depending on maximum dip angle, accuracy condition, and wavenumber. Operator tables are then constructed using the explicit depth extrapolation operators. In a further embodiment, depth migration is performed using the explicit depth extrapolation operators from the operator tables.

Abstract: A set of pre-stack seismic data is downward extrapolated, by first determining a migration interval in the seismic data set. A maximum error criterion is selected for the migration interval. A maximum relative error in phase calculated as a function of frequency, propagation angle, and the relative variation in velocity in the migration interval. The maximum relative error in phase is compared to the maximum error criterion. The type of extrapolation to use in the migration interval is determined from the comparison of the maximum relative error in phase to the maximum error criterion. The type of extrapolation is selected from a set comprising Gazdag phase-shift extrapolation, split-shift Fourier extrapolation, and implicit finite difference extrapolation.

Abstract: A seismic wavefield is extrapolated using variable extrapolation step size and then phase-shifted linear interpolation is applied to the extrapolated wavefield.

Abstract: A method is disclosed for processing seismic data. The method includes determining a position of a seismic energy source and seismic receivers at a time of actuation of the source. A velocity of the seismic receivers with respect to the source position is determined at the time of actuation. An offset of the receivers is corrected using the velocity. A moveout correction is determined for the signals detected by the sensors based on the corrected offset and a velocity of earth media through which seismic energy passed from the source to the sensors.

Abstract: A system or apparatus and method for retrieving cable from water during marine operations is provided that reduces damage to the cable from pulling forces during the retrieval. A pulling device distributes the forces and stresses all along the cable components. In one embodiment, the pulling drive comprises a pulling drum powered by a clutching system or by a hydraulic torque conversion system set to slip or stall at a selectable force value. The apparatus may use a see-saw action to maintain the forces below damaging levels. The system may be adapted for deploying cable in marine operations as well.

Abstract: A method is disclosed for determining interval anisotropic parameters. The method includes determining normal moveout (NMO) velocities and effective anelliptical parameters from seismic data traces. The NMO velocities are processed to obtain interval NMO velocities. The NMO velocities, effective anelliptical parameters and interval NMO velocities are inverted to obtain the interval anisotropic parameters. In one embodiment, the inversion includes damped least squares. In one embodiment, the inversion is preconditioned.

Abstract: A cable for towing marine devices is disclosed. The cable includes a strength member and at least one conduit associated with the strength member. The conduit has apertures therein at selected locations along the conduit. The apertures are adapted to conduct gas from a source into water in which the cable is disposed. Also disclosed is a method for improving the flow of a cable through water. The method includes releasing a gaseous bubble stream proximate an outer surface of said cable while the water is moving relative to the cable.

Abstract: A method and system for interrogating a seismic sensor in a seismic cable having modular sensing stations spaced along the seismic cable and a connection module head end of the sensor sections, that includes dropping, at the connection modules, a wavelength of light from an input bus telemetry fiber that includes multiple wavelengths of light, distributing the dropped wavelength of light to the seismic sensor, returning the dropped wavelength from the seismic sensor to a return telemetry fiber, remultiplexing the dropped wavelength of light onto the return bus telemetry, and amplifying, in the seismic cable, the returned dropped wavelength.

Abstract: A method for attaching seismic sensors in a seismic cable that includes a strength member inside a cable jacket with a fiber tube wound around the strength member and a sensor station base attached around the cable wherein the jacket is removed, at least one fiber tube is extracted and a seismic sensor is attached to the fiber tube.

Abstract: A method of geophysical exploration of a subsurface region of interest which utilizes an unsupervised learning network to organize seismic data representing a subsurface region of interest. A portion of the organized seismic data is correlated with lithological data from a well bore located in said subsurface region of interest and said correlation is applied to said seismic data to estimate lithology in said subsurface region of interest.

Abstract: In a seismic survey, idealized subsurface illumination is generated using idealized survey data. Then, the following three steps are performed during each of a sequence of time intervals during the seismic survey. First, an incremental portion of actual survey data is collected, using data acquisition equipment at a data acquisition location. Second, the incremental portion of actual survey data is communicated from the data acquisition location to a data processing location. Third, an incremental portion of actual subsurface illumination is generated using the incremental portions of actual survey data, to incrementally generate actual subsurface illumination at the data processing location. It is determined if additional data acquisition is desirable by comparison of the idealized subsurface illumination and the actual subsurface illumination, in the data processing location.

Abstract: In connection with a method and a tool for preparing a well for the production of hydrocarbons, it is aimed at perforating a casing portion (26) and working surrounding sediment (80) in a channel-forming manner. For this purpose the tool comprises a drilling means for drilling transverse holes through the casing wall when the tool (10), which is arranged to be raised/lowered and rotated about its longitudinal axis, shared by the casing (26), is placed in a fixed position within the well, through which transverse hole (40) and into surrounding sediment a jetting hose means (42,42a) is arranged to jet/dig its way in a channel-forming manner. The drilling and jetting hose means also have inactive stand-by positions protectively retracted within the tool housing (10a), from and into which they may successively be pushed forward into active working positions and again be withdrawn, as a channel (44) is completed in the sediment (80).

Abstract: A method for seismic surveying is disclosed which includes towing a first seismic energy source and at least one seismic sensor system. A second seismic energy source is towed at a selected distance from the first source. The first seismic energy source and the second seismic energy source are actuated in a plurality of firing sequences. Each of the firing sequences includes firing of the first source, waiting a selected time firing the second source and recording signals generated by the seismic sensor system. The selected time between firing the first source and the second source is varied between successive ones of the firing sequences. The firing times of the first and second source are indexed so as to enable separate identification of seismic events originating from the first source and seismic events originating from the second source in detected seismic signals.

Abstract: A method is disclosed for marine seismic surveying in which a seismic signal is detected in a body of water with a motion sensor and a pressure sensor positioned at a location proximate the bottom of the body of water. Seismic signals are detected with pressure sensors positioned in one or more streamer cables being towed in the body of water near the location proximate the bottom of the water at which a motion sensor and a pressure sensor are positioned. The signals detected by the motion sensor and pressure sensor positioned proximate the bottom of the body of water are used for calibrating the seismic signals detected with the pressure sensors positioned in the streamer cables.

Abstract: A method is disclosed for processing seismic data from concurrently recorded co-located pressure sensors and geophones. The seismic data are processed by first determining an upgoing wavefield and a downgoing wavefield in the seismic data. Adaptive subtraction is then applied to at least one of the upgoing wavefield and the downgoing wavefield to remove the noise from the signal. In alternative embodiments, the upgoing wavefield can be used as a noise model for the downgoing wavefield or the downgoing wavefield can be used as a noise model for the upgoing wavefield.

Abstract: A seismic data set is processed by applying a transform to the seismic data set that corrects for time shifts in the seismic data set resulting from azimuthal variation. Alternatively, a seismic data set is sorted to common offset gathers. Then, the following steps are applied to each common offset gather: A transform is applied to the common offset gather that corrects for time shifts in the common offset gather resulting from azimuthal variation. The transformed common offset gather is inverse transformed.

Abstract: A method is disclosed for separating energy resulting from actuating at least two different seismic energy sources from seismic signals. The sources are actuated to provide a variable time delay between successive actuations of a first one and a second one of the sources. The method includes sorting the seismic signals such that events therein resulting from actuations of the first source are substantially coherent in all spatial directions, coherency filtering the first source coherency sorted signals, sorting the seismic signals such that events therein resulting from actuations of the second source are substantially coherent in all spatial directions, and coherency filtering the second source coherency sorted signals.

Abstract: A method of migration of a seismic data is disclosed. The data include a data point having an input source location, an input receiver location, and a scatter point associated therewith. The method includes determining a projected source location, and determining a projected receiver location. The seismic data point is mapped from an input travel time to a projected travel time. A pseudo-offset is determined based on the projected travel time and the data point is mapped to the pseudo-offset.

Abstract: In one embodiment of the present invention, a drive assembly for a seismic land vibrator is provided. The drive assembly comprises at least a first spring element. The first spring element operates in at least two vibration modes in a seismic frequency band of interest. The drive assembly also comprises a baseplate, a driver, and a reaction mass. The driver interacts with the reaction mass and the first spring element to transfer energy to the baseplate.

Abstract: An apparatus, system, and method are provided for interrogating of optical seismic sensors in a seismic cable. According to various example embodiments of the invention, distribution, return, and amplification of optical signals is performed near sensors for improvement of modularity of construction, signal-to-nose ratios, and simplicity of operations.