Abstract: Method for reconstructing subsurface Q depth profiles from common offset gathers (92) of reflection seismic data by performing migration (40), ray tracing (100), CDP-to-surface takeoff angle finding (96, 98), kernel matrix construction (110), depth-to-time conversion and wavelet stretching correction (80), source amplitude spectrum fitting, centroid frequency shift calculation (90), and box-constrained optimization (120).

Abstract: A method, including: obtaining a velocity model generated by an acoustic full wavefield inversion process; generating, with a computer, a variable Q model by applying pseudo-Q migration on processed seismic data of a subsurface region, wherein the velocity model is used as a guided constraint in the pseudo-Q migration; and generating, with a computer, a final subsurface velocity model that recovers amplitude attenuation caused by gas anomalies in the subsurface region by performing a visco-acoustic full wavefield inversion process, wherein the variable Q model is fixed in the visco-acoustic full wavefield inversion process.

Abstract: Method for estimating reflector dips in a window of post stack image traces (51) of seismic data for use in velocity tomography (57). The method iteratively (56) flattens (55) the image traces against a specified reference trace through the application of conjugate-gradient least-squares inversion (53). Different from other dip estimation methods which emphasize on strong-amplitude reflectors, the inventive method automatically inverts for the reflector dip for every grid point in the image window.

Abstract: A method, including: obtaining a velocity model generated by an acoustic full wavefield inversion process; generating, with a computer, a variable Q model by applying pseudo-Q migration on processed seismic data of a subsurface region, wherein the velocity model is used as a guided constraint in the pseudo-Q migration; and generating, with a computer, a final subsurface velocity model that recovers amplitude attenuation caused by gas anomalies in the subsurface region by performing a visco-acoustic full wavefield inversion process, wherein the variable Q model is fixed in the visco-acoustic full wavefield inversion process.

Abstract: Method for estimating residual moveout in common image gathers (51) of seismic data for use in velocity tomography (57). The method iteratively (56) flattens (55) the common image gathers against a specified reference trace through the application of conjugate-gradient least-squares inversion (53). Different from other picking methods which need to identify and track strong amplitudes, the inventive method automatically inverts for the depth residual for every grid point in the image gather. There is no need to identify and track events.

Abstract: Method for performing a full wavefield inversion (FWI) without simulating free-surface multiple reflections. The free-surface multiples are removed from the field gathers of seismic data, which are then used to generate a subsurface velocity model by FWI. In the FWI, the field monopole sources and receivers are replaced with dipole (actual and mirror image) sources and receivers (21) when model-simulating (23) synthetic survey data. Also, direct arrivals at the mirror receiver locations are preferably simulated (25) with the dipole sources for each shot location and added (26) to the synthetic survey data (24) for that shot location, resulting in corrected synthetic survey data (27), which is used in the FWI to generate residuals. A model update may be computed by back-propagating the residuals by injecting them at both mirror and actual receiver locations.

Abstract: Method for reconstructing subsurface Q depth profiles from common offset gathers (92) of reflection seismic data by performing migration (40), ray tracing (100), CDP-to-Data Domain surface takeoff angle finding (96, 98), kernel matrix construction (110), depth-to-time conversion and wavelet stretching correction (80), source amplitude spectrum fitting, centroid frequency shift calculation (90), and box-constrained optimization (120).

Abstract: Method for estimating reflector dips in a window of post stack image traces (51) of seismic data for use in velocity tomography (57). The method iteratively (56) flattens (55) the image traces against a specified reference trace through the application of conjugate-gradient least-squares inversion (53). Different from other dip estimation methods which emphasize on strong-amplitude reflectors, the inventive method automatically inverts for the reflector dip for every grid point in the image window.

Abstract: A stable method for using fat-ray tomography to determine a high-resolution velocity model of the subsurface from seismic data (71). The velocity model (72) may be used in migrating the seismic data (76) to image the subsurface. Rays are traced from a subsurface reflection point to surface source and receiver locations (73), using Fresnel zone construction methods (74) that honor correct initial conditions, with the Fresnel radius being a function of velocity.

Abstract: Method for estimating residual moveout in common image gathers (51) of seismic data for use in velocity tomography (57). The method iteratively (56) flattens (55) the common image gathers against a specified reference trace through the application of conjugate-gradient least-squares inversion (53). Different from other picking methods which need to identify and track strong amplitudes, the inventive method automatically inverts for the depth residual for every grid point in the image gather. There is no need to identify and track events.

Abstract: A stable method for using fat-ray tomography to determine a high-resolution velocity model of the subsurface from seismic data (71). The velocity model (72) may be used in migrating the seismic data (76) to image the subsurface. Rays are traced from a subsurface reflection point to surface source and receiver locations (73), using Fresnel zone construction methods (74) that honor correct initial conditions, with the Fresnel radius being a function of velocity.