A system and method for forming a seismic image of a subterranean region of interest are provided. The method includes obtaining an observed seismic dataset for the subterranean region of interest and determining a plurality of common-offset sections from the observed seismic dataset. The method further includes determining stochastically migrated common-offset sections for each of the common-offset sections and forming a stochastic image gathers from the plurality of stochastically migrated common-offset sections. The method still further includes forming the seismic image by stacking each of the plurality of stochastically migrated common-offset sections.

Systems and methods for estimating orthorhombic anisotropy parameters of subsurface rock layers are provided. An initial three-dimensional (3D) model of layers in a subsurface formation is generated. Particular combinations of seismic source and receiver locations associated with a vertical seismic profile (VSP) survey of the formation are selected based on a simulation of seismic wave propagation through each layer of the initial 3D model. A global inversion is performed using data points selected from travel time data associated with the VSP survey in order to estimate different sets of anisotropy parameters for the layers of the initial 3D model, where the selected data points correspond to the selected source-receiver combinations. The initial 3D model is refined with an optimal set of anisotropy parameters selected from the estimated parameter sets. The refined 3D model is provided for seismic analysis and well planning operations to be performed for the subsurface formation.

A system and method for predicting the front arrival time in seismic monitoring is disclosed The method includes measuring or computing a physical property reference signature at a calibration point, the physical property reference signature based on a change in a physical property over time due to a well injection; computing a seismic attribute reference signature at the calibration point based on the physical property reference signature; identifying a reference marker, the reference marker corresponding to a change in the seismic attribute reference signature at the calibration point over time; detecting a measured marker, the measured marker corresponding to a change in a seismic attribute of a recorded dataset over time; calibrating the measured marker; and calculating a marker arrival time for a location other than the calibration point.

Systems and methods for time preserving full waveform inversion are disclosed. The methods may include acquiring, using a seismic acquisition system, a seismic dataset and, using a seismic processor, obtaining, from the seismic dataset, an event in two-way traveltime (TWT) and a velocity model in TWT, and converting the velocity model in TWT into a velocity model in depth. The methods further include producing a final velocity model in depth, where the final velocity model is produced using a full waveform inversion (FWI), the velocity model in depth, and a TWT-preserving method preserves the event in TWT at each iteration of the FWI; and forming a seismic image in depth using the final velocity model in depth and the seismic dataset. The methods further include identifying, using a seismic interpretation workstation and based on the seismic image in depth, a drilling target; and planning a borehole path to the drilling target.

A method may include obtaining various cross-spread gathers regarding a geological region of interest. The method may further include determining traveltime table data based on the cross-spread gathers. The method may further include transmitting the cross-spread gathers to various parallel processing groups in a parallel processing network. A respective cross-spread gather among the cross-spread gathers may be transmitted to a respective parallel processing group among the parallel processing groups. The method may further include determining, by various parallel processing nodes in the respective parallel processing group, a first subset of a migrated dataset using the respective cross-spread gather, a subset of the traveltime table data, a velocity model, and a migration function. The method may further include generating, based on various subsets of the migrated dataset that includes the first subset, a first seismic image of the geological region of interest.

Method and apparatus for performing a traveltime-based seismic full waveform inversion using the frequency-dependent Hann window and the source-independent scheme to generate a final velocity model of subsurface formations are provided. The method includes positioning seismic data recording sensors in the survey region; blasting at points of incidence in the survey region to generate seismic waves; and sensing and recording the seismic waves using the seismic data recording sensor. The recorded seismic waves are seismic data. The method further includes transmitting the seismic data to a computer system including one or more memories and storing the seismic data in one or more memories; storing a source wavelet in the one or more memories; performing, by the computer system, a forward modeling operation using the source wavelet; and generating, by the computer system, the final velocity model using the seismic full waveform inversion with the forward modeling operation.

Methods and systems are disclosed. The methods may include obtaining a seismic dataset with a plurality of dimensions pertaining to a subterranean region of interest and forming a plurality of spatial nodes within the seismic dataset. The method may further include determining, for each node, a traveltime operator, based on a portion of the seismic dataset within an aperture surrounding the node, assigning a canonical operator based on the traveltime operator, and forming a plurality of windows containing a neighboring node. For each window, the method may include determining a modal canonical operator, based on the canonical operator for each neighboring node, determining modal-nodes and deviating-nodes within the window, and determining a replacement traveltime operator for each deviating-node. The method may still further include forming a seismic image based on the seismic dataset, the traveltime operator of the modal-nodes, and the replacement traveltime operator of the deviating-nodes.

A method for imaging the Earth's subsurface includes taking summed recordings of signals acquired by a plurality of seismic sensors disposed above the volume in response to repeated actuations of a seismic energy source. A travel time of seismic energy is determined from a position of the source to a selected image point in the volume and from the image point to each seismic sensor. A time-delayed scanline gather is generated from the travel times using a model of spatial distribution of acoustic properties of formations in the volume. A template image of backscattered energy from the image point is generated based on the model. The flattened scanline gather is singular value decomposed. The template image is projected onto the decomposed time-delayed scanline gather. Components from the projection are used to determine signal and interference. Weights are calculated for beamforming of the determined signal component. The weights and delay times are used to cause the focal point of the beamforming to be at the image point.

A method, system, and non-transitory computer readable media for seismic imaging of a subterranean formation. The operations include receiving data representing seismic traces corresponding to seismic waves propagating in the subterranean formation, and determining, from the seismic traces, travel time data and a data covariance matrix. The operations include determining a prior velocity model and a prior model covariance matrix for common midpoint locations and generating an objective function based on the travel time data, the data covariance matrix, the prior velocity model, and the prior model covariance matrix. The operations include determining, by minimizing the objective function, values for one-dimensional velocity models and a set of accuracy values. The operations include generating a pseudo-3D model and a set of accuracy values for the pseudo-3D model. Based on the pseudo-3D model and the set of accuracy values for the pseudo-3D model, a seismic image representing the subterranean formation is generated.

Apparatus and methods are provided including a system that includes multiple seismic sensors and a processor. The processor receives respective seismograms from the seismic sensors during a seismic disturbance and identifies, based on the seismograms, respective estimated P-wave arrival times for at least some of the seismic sensors. Based on the estimated P-wave arrival times, the processor defines one or more virtual arrays, each of which includes at least three of the seismic sensors. The processor computes respective back azimuths for the virtual arrays, and based on the estimated P-wave arrival times and back azimuths, computes estimated coordinates of a focus of the seismic disturbance or of a point on a surface of Earth above the focus. The processor outputs an output based on the coordinates. Other applications are also described.