Abstract: The present invention relates to a sensing system, in particular to sensing system for sensing undersea seismic events. A vibration sensor is provided for sensing seismic vibrations on the sea bed is provided. The vibration sensor is electrically coupled to a transmitter unit, the transmitter unit being arranged to transmit, in use, an acoustic wave from which the presence of a seismic vibration can be inferred. The acoustic wave modulates light travelling along a nearby optical cable, the modulation being recovered at a distant monitoring station. A flotation arrangement is provide for retaining the transmitter unit in a raised position relative to the sea bed to facilitate the coupling of the acoustic wave to the optical cable.

Abstract: An acoustic borehole logging system for generation and detection of multipole modes used to determine elastic properties of earth formations characterized as inhomogeneous anisotropic solids. The system concurrently generates and senses monopole, dipole, quadrupole and any higher order pole in the borehole/formation system in order to characterize the elastic properties and stress state of material penetrated by the borehole. Multipole modes of all orders are induced simultaneously without the need for separate transmitter and receiver systems. Performance of the logging system is not compromised due to eccentering of the axis of the tool in the borehole, tool tilt with respect to the axis of the borehole, or mismatch of response sensitivity of multiple receivers within the tool.

Abstract: Various methods are disclosed for identifying faults in a seismic data volume. In some method embodiments, the fault identification method comprises determining a planarity value for each of multiple positions of an analysis window in the data volume. The planarity value may be indicative of the planarity of discontinuities in the analysis window, and may be further filtered by limits on the verticality and centrality of the discontinuities. Thus a filter may be determined for suppressing relatively non-planar, relatively non-vertical, and relatively un-centered discontinuities from a discontinuity display, thereby enhancing a display of faults present in the seismic data volume.

Abstract: A walkaway VSP survey is carried out with receivers located in a borehole near the base salt. Reflection tomographic inversion of data from the walkaway VSP is used to derive a velocity model for the subsurface and may be used for imaging of sub-salt reflections.

Abstract: Seismic data recorded by subsurface seismic sensors placed in a borehole, such as an oil or gas well, are transformed via a process of upward wavefield propagation to pseudo-receivers at the surface of the earth. The seismic data thus transformed can be processed as though the data had been recorded by the pseudo-receivers at the surface rather than in the borehole where the data were actually recorded. This method accurately accounts for seismic source statics, anisotropy, and all velocity effects between the real receivers in the borehole and the pseudo-receivers at the surface of the earth.

Abstract: Apparatus and methods are described for remotely controlling position of marine seismic equipment. One apparatus comprises a source connected to a tow member; and an adjustment mechanism connected to the source and the tow member, the adjustment mechanism adapted to actively manipulate an angle of attack of the source. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: Time slices of seismic data are transformed from rectangular space-time domain to cylindrical space-time domain. 2-D seismic migration is performed on the transformed data for each radial direction. Slices of the migrated data are inverse transformed back to the rectangular space-time domain, generated migrated 3-D data for generally inhomogeneous media.

Abstract: An apparatus and method for seismic data acquisition is provided, which, in one aspect, define a plurality of attributes relating to acquisition of seismic data by the apparatus, determine a value of each attribute when the apparatus is deployed for acquiring seismic data, generate a message for each attribute whose determined value meets a selected criterion, and transmit wirelessly each generated message to a remote unit without solicitation of such a message by the remote unit. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A seabed region (18) that lies under a seabed surface area of over one square meter, is analyzed by comparing a core sample taken near the middle of the region and/or data from a geotechnical insitu cone penetrometer installed at the middle of the region, to an acoustic analysis of the region. Locations of the acoustic analysis are precisely correlated to the location of the core test sample or cone test by mounting an acoustic imaging apparatus (16) that holds acoustic transducers (44, 46), on a carriage (26) that is positioned on the core drill (12) or cone penetrometer barrel staff. The carriage of the acoustic imager apparatus is clamped to the core drill when the core drill is not rotating. An arm (30 and/or 32) is supported on the carriage through a frame (28), with at least one acoustic generator (44) and one acoustic echo detector (46) mounted on the arm. The arm can be rotated to positions lying about the drill axis (14) to accurately scan a wide area.

Abstract: A method is described for reducing multiples in marine seismic data using at least two sets of signals representing seismic energy reflected and/or refracted from an earth structure using a plurality of seismic receivers located in a body of water with the two sets differing in the traveltime of signals through the body of water, separating said signals into up- and down-going wavefields and combining the two sets to remove multiples.

Abstract: A seabed seismic source apparatus includes a control module adapted for deployment at a seabed. The control module has a receiver for receiving a remote signal and a firing controller for generating a firing signal in response to the remote signal. The seabed seismic source apparatus further includes at least one seismoacoustic source module adapted for deployment at the seabed with the control module. The seismoacoustic source module has a seismoacoustic source for generating a seismic signal and a firing device for firing the seismoacoustic source to generate the seismic signal. The seabed seismic source apparatus further includes a transmission link between the firing controller and the firing device, wherein the firing device fires the seismoacoustic source upon receiving the firing signal generated by the firing controller.

Abstract: The present invention relates to streamer cables. One embodiment of the present invention relates to a method for preparing a streamer cable. The method may comprise retrofitting the streamer cable with a solid void-filler material, where the streamer cable was configured as a liquid-filled streamer cable. The retrofitting may comprise introducing a void-filler material into the streamer cable when the void-filler material is in a liquid state and curing or otherwise solidifying the void-filler material to a solid state. In another embodiment, the present invention relates to a streamer cable comprising an outer skin and at least one sensor positioned within the outer skin. The streamer cable may also comprise a solid void-filler material positioned between the outer skin and the at least one sensor, wherein the solid void-filler material is coupled to the at least one sensor.

Abstract: A combined electromagnetic acoustic transducer (EMAT) is disclosed adapted to generate both SH-type acoustic waves and LAMB-type acoustic waves in a conductive casing, surroundings of which are to be analyzed. The transducer comprises one magnet assembly and two RF coils implemented as multi-layer printed circuit board. Each coil is used to generate or receive acoustic signals of one wave type. Compared to using two single-wave-type transducers the combined EMAT significantly reduces total attraction force to the casing and, correspondingly, simplifies mechanics of the measurement tool. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method and computer instructions on computer readable media for determining and analyzing spatial changes in the earth's subsurface associated with dip vectors measured using 3D data in regions near a fluid contact or seismic flat spot event. The method obtains seismic attribute data, then derives corresponding 3D dip and azimuth as a 3D volume and derives corresponding 3D reliability volumes or 3D censor volumes. A set of vector is formed within a local subvolume of interest interior to the focused subvolume of interest for each reliability location, and a subset of local vectors within a user specified deviation of the azimuth of the structural dip vector are identified. A set of candidate flat spot dip vectors within the local subvolume of interest are identified enabling a significance measure for each vector within the set of candidate flat spot dip vectors to be determined.

Abstract: Downhole positioning systems and associated methods are disclosed. In some embodiments, the system comprises a downhole source, an array of receivers, and a data hub. The downhole source transmits an electromagnetic positioning signal that is received by the array of receivers. The data hub collects amplitude and/or phase measurements of the electromagnetic positioning signal from receivers in the array and combines these measurements to determine the position of the downhole source. The position may be tracked over time to determine the source's path. The position calculation may take various forms, including determination of a source-to-receiver distance for multiple receivers in the array, coupled with geometric analysis of the distances to determine source position. The electromagnetic positioning signal may be in the sub-hertz frequency range.

Abstract: Methods and apparatus for creating a velocity profile of a formation surrounding a borehole by checkshot measurements while moving the tool along the borehole. A conveyance and a sensor section are configured to move the sensor section in the borehole. At least one receiver is configured to detect signals generated at or near the surface while the sensor section is moving in the borehole.

Abstract: Signals of pressure sensors and particle motion sensors located in marine seismic streamers are combined to generate a seismic wavefield. At least a part of the particle motion sensor signal is calculated from a recorded pressure signal and the calculated at least a part of the particle motion sensor signal is used to generate a particle motion sensor signal in which noise is substantially attenuated in at least a lower frequency range thereof. The pressure sensor data and the noise attenuated particle motion sensor signal can then be combined to calculate up- and down-going wavefields.

Abstract: A method for obtaining seismic data is disclosed. A constellation of seismic energy sources is translated along a survey path. The seismic energy sources include a reference energy source and a satellite energy source. The reference energy source is activated and the satellite energy source is activated at a time delay relative to the activation of the reference energy source. This is repeated at each of the spaced apart activation locations along the survey path to generate a series of superposed wavefields. The time delay is varied between each of the spaced apart activation locations. Seismic data processing comprises sorting the traces into a common geometry domain and replicating the traces into multiple datasets associated with each particular energy source. Each trace is time adjusted in each replicated dataset in the common-geometry domain using the time delays associated with each particular source.

Abstract: A method of characterizing a fractured reservoir in a field includes measuring seismic reflection coefficient of the fractured reservoir as a function of angle of incidence and azimuth, predicting seismic reflection coefficient of the fractured reservoir as a function of angle of incidence and azimuth using an elastic stiffness tensor and an elastic compliance tensor of the fractured reservoir, determining components of an excess compliance tensor due to the presence of fractures in the fractured reservoir by matching the predicted seismic reflection coefficient to the measured seismic reflection coefficient, and characterizing one or more properties of the fractured reservoir using the excess compliance tensor.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.