A method for subsurface fault extraction using undirected graphs is provided. Extracting faults in the subsurface may assist in various stages of geophysical prospecting. To that end, an undirected graph may be used in order to identify distinctive fault branches in the subsurface. Fault probability data, from seismic data, may be used to establish connections in the undirected graph. Thereafter, some of the connections in the undirected graph may be removed based on analyzing one or more attributes, such as dip, azimuth, or context, associated with the connections or nodes associated with the connections. After which, the undirected graph may be analyzed in order to extract the faults in the subsurface.

Velocity tomography using time lags of wave equation migration is disclosed. Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves by generated a migration velocity model from a multitude of observations using combinations of source and receiver locations. The migration velocity model may be updated in order to reduce depth differences of reflection events (also called residual depth errors (RDE)). Direct measurement of RDE may be difficult in certain complex subsurface areas. In such areas, the RDE may be reconstructed based on time lags of wave equation migration and then used to update the migration velocity model. In particular, the RDE may be directly reconstructed from the time lags of wave equation migration, such as based on a direct relation between RDE and the time lags.

A method for partitioning a search direction when using least squares reverse time migration (LSRTM) is provided. LSRTM may be used iteratively in order to improve imaging accuracy. As part of LSRTM, multiple local line searches may be performed. In particular, image space may be partitioned, such as by using a set of masks. The search direction, such as the gradient, may be partitioned using the set of masks. Local line searches may be performed for each partition of the search direction, resulting in finding respective line search constants. The respective line search constants may then be used for iterating the model in order to improve imaging accuracy.

Hydrocarbon exploration and extraction can be facilitated using machine-learning models. For example, a system described herein can receive seismic data indicating locations of geological bodies in a target area of a subterranean formation. The system can provide the seismic data as input to a trained machine-learning model for determining whether the target area of the subterranean formation includes one or more types of geological bodies. The system can receive an output from the trained machine-learning model indicating whether or not the target area of the subterranean formation includes the one or more types of geological bodies. The system can then execute one or more processing operations for facilitating hydrocarbon exploration or extraction based on the seismic data and the output from the trained machine-learning model.

Disclosed herein are geologic modeling methods and systems employing function-based representations of horizons intersected by partial faults. An illustrative method embodiment includes: (a) obtaining a seismic image volume; (b) identifying a horizon within the seismic image volume, said horizon being intersected by a partial fault; (c) deriving a function-based representation of the horizon, the representation being continuous except across the partial fault; (e) constructing a watertight subsurface model using the function-based representation; (f) assigning petrophysical parameter values to compartments of the watertight subsurface model; and, optionally, (g) storing or displaying the watertight subsurface model.

The present invention relates to a method of modelling a sedimentary basin by means of a numerical basin simulation solving at least a balance equation of poromechanics according to a face-based smoothed finite-element method for determining at least a stress field and a deformation field. The method according to the invention notably comprises the following steps: subdividing the hexahedral cells of a mesh representation of a state of the basin into at least eight hexahedral subcells, determining a transition relation between the degrees of freedom of the nodes of the subcells and the degrees of freedom of the nodes of the cell to which the subcells belong, and determining a stiffness and nodal forces from at least this transition relation and a strain-displacement relation determined for the subcells.

Systems and methods develop a three-dimensional model of a subterranean formation based on vertical seismic profiles at a plurality of well locations. This approach can include receiving seismic data for the subterranean formation including the vertical seismic profiles; for each vertical seismic profile, injecting a ground force into the vertical seismic profile to provide a reference trace at depth zero to estimate energy loss in each receiver providing data in the vertical seismic profile and estimating time and depth variant quality factors for the well location associated with the vertical seismic profile based on the seismic profile; estimating quality factors for points within a three-dimensional volume representing the subterranean formation by interpolating between the time and depth variant quality factors for the location associated with each vertical seismic profile; and combining estimated quality factors to generate a three-dimensional quality factor model of the three-dimensional volume representing the subterranean formation.

Methods, apparatus, and systems for mapping surface and near surface features and processing artifacts from stacked and processed seismic data are disclosed. In some implementations, a computer system receives a three-dimensional (3D) seismic cube including seismic reflectivity data obtained at a geographical location. The computer system generates a vertical analysis window of the 3D seismic cube. The computer system extracts a second 3D seismic cube from the seismic reflectivity data based on the vertical analysis window. The second 3D seismic cube has multiple vertical amplitude traces associated with the seismic reflectivity data. The computer system generates 3D data comprising multiple frequency traces from the multiple vertical amplitude traces using a domain transform. The computer system generates a two-dimensional (2D) map from the 3D data. The 2D map represents geographical features of the geographical location.

A system for seismic imaging of a subterranean geological formation, the system includes a receiver configured to obtain seismic data comprising a data volume representing a post-stacked image. The system includes a filtering module configured to: apply frequency-wavenumber (F-K) filter to the data volume extract a negative-dip structure image and apply the frequency-wavenumber (F-K) filter to the data volume extract a positive-dip structure image. The system includes a diffraction rendering module configured to: multiply the positive-dip structure image with the negative-dip structure image and generate a diffraction-enhanced seismic image representing a geological formation of the data volume.

Geologic modeling methods and systems may use design-space to design-space mapping to facilitate simulation grid generation for multiple interpretations of a subsurface region. As one example, one or more embodiments of a geologic modeling method may comprise: obtaining first and second geologic models having different structural interpretations of a subsurface region; mapping each of the geologic models to associated design space models representing an unfaulted subsurface region; determining a design-to-design space mapping from the first design space model to the second design space model; using said mapping to copy parameter values from the first design space model to the second of the design space model; gridding each of the design space models to obtain design space meshes; partitioning cells in the first and second design space meshes along faults; reverse mapping the partitioned design space meshes to the physical space to obtain first and second physical space simulation meshes.