Abstract: Methods and systems described herein are directed to determining properties of a subterranean formation using an acoustic wave-equation with a novel formulation in terms of a velocity model and a reflectivity model of the subterranean formation. The acoustic wave equation may be used with full-waveform inversion to simultaneously build velocity and reflectivity models of a subterranean formation. The velocity and reflectivity models may be employed for quantitative interpretation. The velocity and reflectivity models may be employed to determine impedance and density of the subterranean formation for prospectivity assessment. The acoustic wave equation may be also used with least-squares reverse time migration in the image or data domains, to build a reflectivity model of the subterranean formation with enhanced resolution and amplitude fidelity.

Abstract: Methods and systems described herein are directed to determining properties of a subterranean formation using an acoustic wave-equation with a novel formulation in terms of a velocity model and a reflectivity model of the subterranean formation. The acoustic wave equation may be used with full-waveform inversion to build high-resolution velocity and reflectivity models of a subterranean formation. The acoustic wave equation may be also used with least-squares reverse time migration in the image and space domains, to build a reflectivity model of the subterranean formation with enhanced resolution and amplitude fidelity. The velocity and reflectivity models of materials that form the subterranean formation reveal the structure and lithology of features of the subterranean formation and may reveal the presence of oil and natural gas reservoirs.

Abstract: Disclosed are advantageous designs for highly-sparse seabed acquisition for imaging geological structure and/or monitoring reservoir production using sea surface reflections. The highly-sparse geometry designs may be adapted for imaging techniques using the primary and higher orders of sea surface reflection and may advantageously allow for the use of significantly fewer sensors than conventional seabed acquisition. The highly-sparse geometry designs may be relevant to 3D imaging, as well as 4D (“time-lapse”) imaging (where the fourth dimension is time). In accordance with embodiments of the invention, geophysical sensors may be arranged on a seabed to form an array of cells. Each cell in the array may have an interior region that contains no geophysical sensors and may be sufficiently large in area such that a 500 meter diameter circle may be inscribed therein.

Abstract: This disclosure describes processes and systems for generating a high-resolution velocity model of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. A velocity model is computed by iterative FWI using reflections, resolving the velocity field of deep subterranean targets without requiring ultralong offsets. The processes and systems use of an impedance sensitivity kernel to characterize reflections in a modeled wavefield, and then use the reflections to compute a velocity sensitivity kernel that is used to produce low-wavenumber updates to the velocity model. The iterative process is applied in a cascade such that position of reflectors and background velocity are simultaneously updated. Once the low-wavenumber components of the velocity model are updated, the velocity model is used as an input of conventional FWI to introduce missing velocity components (i.e., high-wavenumber) to increase the resolution of the velocity model.

Abstract: This disclosure describes processes and systems for generating a seismic image of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. The seismic data comprises recorded pressure and vertical velocity wavefields that are used to separate the recorded pressure wavefield into upgoing and downgoing pressure wavefields. A seismic image is computed from the subterranean formation based on a product of the downgoing pressure wavefield and a migration operator applied to the upgoing pressure wavefield. The downgoing pressure wavefield is a boundary source wavefield and the upgoing pressure wavefield is boundary receiver wavefield of the migration operator. The seismic image is iteratively updated by computing a residual seismic image based on the upgoing pressure wavefield and adding the residual seismic image to the seismic image.

Abstract: Disclosed are advantageous designs for highly-sparse seabed acquisition for imaging geological structure and/or monitoring reservoir production using sea surface reflections. The highly-sparse geometry designs may be adapted for imaging techniques using the primary and higher orders of sea surface reflection and may advantageously allow for the use of significantly fewer sensors than conventional seabed acquisition. The highly-sparse geometry designs may be relevant to 3D imaging, as well as 4D (“time-lapse”) imaging (where the fourth dimension is time). In accordance with embodiments of the invention, geophysical sensors may be arranged on a seabed to form an array of cells. Each cell in the array may have an interior region that contains no geophysical sensors and may be sufficiently large in area such that a 500 meter diameter circle may be inscribed therein.

Abstract: Disclosed are advantageous designs for highly-sparse seabed acquisition for imaging geological structure and/or monitoring reservoir production using sea surface reflections. The highly-sparse geometry designs may be adapted for imaging techniques using the primary and higher orders of sea surface reflection and may advantageously allow for the use of significantly fewer sensors than conventional seabed acquisition. The highly-sparse geometry designs may be relevant to 3D imaging, as well as 4D (“time-lapse”) imaging (where the fourth dimension is time). In accordance with embodiments of the invention, geophysical sensors may be arranged on a seabed to form an array of cells. Each cell in the array may have an interior region that contains no geophysical sensors and may be sufficiently large in area such that a 500 meter diameter circle may be inscribed therein.

Abstract: Inversion for marine seismic imaging of a full reflected wavefield can include generating an image of a subsurface formation by full wavefield migrating a recorded seismic wavefield and generating numerically modeled data using the image. A mismatch between the numerically modeled data and the seismic wavefield can be determined. Responsive to determining that the mismatch exceeds an inversion match threshold, the image can be updated using the mismatch between the numerically modeled data and the seismic wavefield.

Abstract: Methods and systems described herein are directed to determining properties of a subterranean formation using an acoustic wave-equation with a novel formulation in terms of a velocity model and a reflectivity model of the subterranean formation. The acoustic wave equation may be used with full-waveform inversion to build high-resolution velocity and reflectivity models of a subterranean formation. The acoustic wave equation may be also used with least-squares reverse time migration in the image and space domains, to build a reflectivity model of the subterranean formation with enhanced resolution and amplitude fidelity. The velocity and reflectivity models of materials that form the subterranean formation reveal the structure and lithology of features of the subterranean formation and may reveal the presence of oil and natural gas reservoirs.

Abstract: Amplitude-versus-angle analysis for quantitative interpretation can include creation of a plurality of angle gathers from imaging a subsurface location with multiples in a near-offset range and imaging primaries outside the near-offset range and application of an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the subsurface location.

Abstract: Amplitude-versus-angle analysis for quantitative interpretation can include creation of a plurality of angle gathers from imaging a subsurface location with multiples in a near-offset range and imaging primaries outside the near-offset range and application of an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the subsurface location.

Abstract: Methods and systems of generating seismic images from primaries and multiples are described. Methods separate pressure data into up-going pressure data and down-going pressure data from pressure data and vertical velocity data. Irregularly spaced receiver coordinates of the down-going and up-going pressure data are regularized to grid points of a migration grid and interpolation is used to fill in down-going and up-going pressure data at grid points of the migration grid. A seismic image is calculated at grid points of the migration grid based on the interpolated and regularized down-going pressure data and the interpolated and regularized up-going pressure data. The seismic images are high-resolution, have lower signal-to-noise ratio than seismic images generated by other methods, and have reduced acquisition artifacts and crosstalk effects.

Abstract: Inversion for marine seismic imaging of a full reflected wavefield can include generating an image of a subsurface formation by full wavefield migrating a recorded seismic wavefield and generating numerically modeled data using the image. A mismatch between the numerically modeled data and the seismic wavefield can be determined. Responsive to determining that the mismatch exceeds an inversion match threshold, the image can be updated using the mismatch between the numerically modeled data and the seismic wavefield.

Abstract: Amplitude-versus-angle analysis for quantitative interpretation can include creation of a plurality of angle gathers from imaging a subsurface location with multiples in a near-offset range and imaging primaries outside the near-offset range and application of an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the subsurface location.

Abstract: The present disclosure is related to a velocity model update with a full waveform inversion gradient. At least one method can include updating a velocity model of a subsurface, which can include suppressing high wavenumber components of the velocity model provided by reflected energy with a decomposed full waveform inversion gradient. Low wavenumber components can be preserved in the velocity model.

Abstract: This disclosure describes processes and systems for generating a seismic image of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. The seismic data comprises recorded pressure and vertical velocity wavefields that are used to separate the recorded pressure wavefield into upgoing and downgoing pressure wavefields. A seismic image is computed from the subterranean formation based on a product of the downgoing pressure wavefield and a migration operator applied to the upgoing pressure wavefield. The downgoing pressure wavefield is a boundary source wavefield and the upgoing pressure wavefield is boundary receiver wavefield of the migration operator. The seismic image is iteratively updated by computing a residual seismic image based on the upgoing pressure wavefield and adding the residual seismic image to the seismic image.

Abstract: This disclosure describes processes and systems for generating a high-resolution velocity model of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. A velocity model is computed by iterative FWI using reflections, resolving the velocity field of deep subterranean targets without requiring ultralong offsets. The processes and systems use of an impedance sensitivity kernel to characterize reflections in a modeled wavefield, and then use the reflections to compute a velocity sensitivity kernel that is used to produce low-wavenumber updates to the velocity model. The iterative process is applied in a cascade such that position of reflectors and background velocity are simultaneously updated. Once the low-wavenumber components of the velocity model are updated, the velocity model is used as an input of conventional FWI to introduce missing velocity components (i.e., high-wavenumber) to increase the resolution of the velocity model.

Abstract: A method for migrating three dimensional seismic data in tilted transversely isotropic media (“TTI”) is based on generating numerical solutions to an exact relationship for a three dimensional dispersion relationship of seismic energy traveling through TTI media. The numerical solutions use selected input values of polar angle and azimuth angle of a transverse isotropic axis of symmetry, and selected values of Thomsen anisotropic parameters to generate tables of numerical values. Based on the tables of numerical values, optimized coefficients for a finite-difference relationship are estimated along multiple splitting directions. The seismic data are then migrated using a three dimensional Fourier finite difference extrapolation algorithm.

Abstract: Techniques are disclosed relating to geophysical analysis. In one embodiment, a method includes receiving seismic data for a geophysical formation recorded during a seismic survey using one or more seabed sensors and one or more sources. In this embodiment, the method includes determining a seismic gather for a location in the geophysical formation, modifying the seismic gather by interchanging source-receiver definitions for the seismic gather, and imaging the location using the modified gather. In this embodiment, the imaging uses higher-order reflections recorded in the seismic gather. In some embodiments, the method includes separating up-going and down-going wavefields and separately imaging using the up-going wavefield and the down-going wavefield.

Abstract: The present disclosure is related to a velocity model update with a full waveform inversion gradient. At least one method can include updating a velocity model of a subsurface, which can include suppressing high wavenumber components of the velocity model provided by reflected energy with a decomposed full waveform inversion gradient. Low wavenumber components can be preserved in the velocity model.