Abstract:
The technologies described herein include systems and methods for performing a first seismic survey and performing a second seismic survey after a predetermined amount of time has lapsed between the first seismic survey and the second seismic survey. The shot times and the shot positions of the second seismic survey may be substantially the same as the shot times and the shot positions of the first seismic survey. After performing the seismic surveys, seismic data generated by the first seismic survey may be processed to generate a first image, and seismic data generated by the second seismic survey may be processed to generate a second image. After generating the first and second images, a difference between the first image and the second image may be computed to generate a time lapse difference image.
Abstract:
A method of evaluating a seismic survey to be carried out at a particular survey location comprises choosing an initial seismic surveying arrangement. One or more parameters of AVO (amplitude versus offset) uncertainty are then determined from the seismic surveying arrangement using a model of the earth's interior at the survey location. If the parameter(s) of AVO uncertainty are not acceptable the seismic surveying arrangement is changed, and the AVO uncertainty parameter(s) re-determined for the new acquisition geometry. The determination of the AVO uncertainty parameter(s) may make use of prior information such as the noise covariance and/or model covariance. This enables the AVO uncertainty parameters to be estimated independent of any seismic data.
Abstract:
A method and apparatus for use in seismic prospecting are disclosed. The method comprises partitioning a plurality of converted split shear-wave data resulting from a common event and recorded at a plurality of azimuths and a plurality of offsets as a function of the azimuths and offsets; separating fast and slow split shear-wave wavefields in the partitioned data; deriving at least one attribute of at least one of the separated fast and slow shear-wave wavefields; and analyzing the derived attribute. The apparatus comprises, in one aspect, a program storage medium encoded with instruction that perform the method when executed by a computing device or a computer programmed to perform the device.
Abstract:
The present invention presents a method for determining shallow water flow risk using seismic data. The seismic data can be processed to enhance its stratigraphic resolution by sub-sampling the seismic data to less than a two-millisecond interval. Performing a stratigraphic analysis on the seismic data and evaluating the seismic attributes of the seismic data can be used to select a control location. A pre-stack waveform inversion is applied to seismic data at a selected control location to provide an elastic model, which includes pressure-wave velocity and shear-wave velocity. The shallow water flow risk is then determined using the elastic model by comparing the pressure-wave velocity to the shear-wave velocity. A post-stack inversion can be applied on the seismic data using the elastic model to model a 3D volume to determine the shallow water flow risk across the 3D volume.
Abstract:
This invention removes the effects of variable water velocity by calculating and applying corrections that map the seismic data to an ideal case of constant water velocity. All of the corrections assume, from a separate analysis step, that the vertical (zero-offset) timing errors induced by the water-velocity variations and that the zero-offset water bottom times are available. Equivalently, the water velocities are assumed known. The timing errors and water velocities are related. The zero-offset water-bottom times are also assumed available. From this information, and an arbitrarily-defined nullidealnull water velocity, it is possible to calculate an observed (actual) water velocity relative to the nullidealnull case. The only additional information needed is the angle of the ray path through the water layer. The angle may be calculated directly from normal moveout velocities derived from conventional analysis of the seismic data, and the information above. A time-dependent and offset-dependent correction may be derived for each sample of the seismic data prior to normal moveout correction.
Abstract:
A technique includes receiving first data acquired by at least a particle motion gradient sensor or a rotation sensor of a streamer that is subject to vibration due to towing of the streamer; and receiving second data acquired by at least one particle motion sensor of the streamer and being indicative of particle motion and vibration noise. The technique includes processing the second data in a processor-based machine to, based at least in part on the first data, attenuate the vibration noise indicated by the second data to generate third data indicative of the particle motion.
Abstract:
Separating survey data for multiple survey sources where first survey data along a first axis measured by a survey sensor device is received, the first survey data responsive to activations of the plurality of survey sources at respective azimuths with respect to the survey sensor device. Second survey data is rotated towards a first azimuth of a first of the plurality of survey sources. The rotated second survey data is used as a model of interference caused by a subset of the plurality of survey sources excluding the first survey source. In other examples, a time dithering technique is performed to separate survey data for multiple survey sources.
Abstract:
A technique includes generating vibroseis sweeps for a vibroseis survey to produce seismic data acquired in response to seismic signals produced by the sweeps. The generation of the vibroseis sweeps including temporally arranging the sweeps into time-overlapping groups. The technique includes regulating a timing of the groups relative to each other based on a slip time. The technique also includes regulating a timing of the sweeps of each group such that consecutive sweep firings of each group are spaced apart by a time substantially less than the slip time.
Abstract:
A marine seismic streamer comprising a solid, hydrophobic core member that is encased in a hydrophobic streamer skin/casing. The hydrophobic streamer skin may be extruded onto and/or heat welded to the hydrophobic core member. The hydrophobic streamer skin/casing may comprise a thermoplastic polyurethane that includes fluorine and/or silicon moieties, silicon, polydimethylsiloxane or the like. The hydrophobic streamer skin/casing may reduce the drag of the streamer and may provide anti-biofouling properties to the streamer. A hydrophobic paint, coating or polymer may in some instances be disposed on top of the hydrophobic streamer skin/casing.
Abstract:
Apparatus and methods for acquiring seismic data using a seabed seismic data cable positioned on a seabed are described, including correcting for the effect of one or more sensor non-linear motions, which improves accuracy of seismic data. One or multiple non-linear movements of the sensor may be corrected for. 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.