Zestani is one of ZTerra’s software tools for estimating Thomsen weak elastic anisotropy parameters and building an initial anisotropic velocity model using well logs, seismic data, and an initial isotropic velocity model in time or in depth. Zestani estimates seismic anisotropy parameters by migrating traces with common midpoints near wells using the vertical velocity derived from well logs or check shots, scans over moveout curves to detect local anisotropy parameters, and then interpolates between these locations to define the anisotropy parameters everywhere in the volume.
ZTerra’s suite of software products includes the ability to perform Kirchhoff migration while specifying these parameters for the following three types of anisotropy models and the ability to perform tomographic velocity model updates while specifying these parameters for the former two of the following three types of anisotropy models:
 Vertical Transverse Isotropy is a special case of the latter cases in which wavepropagation in the medium is isotropic along a vertical local axis of symmetry and symmetrically anisotropic about that axis.
 Tilted Transverse Isotropy is a general case of the former case in which wavepropagation in the medium is isotropic along a tilted local axis of symmetry and symmetrically anisotropic about that axis.
 Orthorhombic Symmetry is a more general case of the former cases in which wavepropagation in the medium is isotropic along three mutually orthogonal axes of symmetry and symmetrically anisotropic about those axes.


Zestani extracts and migrates traces with common midpoints near wells using velocities derived from well logs and then scans over residual moveout curves in order to estimate correlated local anisotropy parameters. Users then interactively edit epsilon and delta picks and interpolate between well locations to define the parameters within the entire volume. With anisotropy parameters estimated everywhere in the volume, Zestani is able to translate velocities known at well locations into events migrated to their true subsurface locations.


Estimate seismic anisotropy for an initial velocity model
 Automatically extract nearwell traces for target migration
 Target oriented Kirchhoff PSDM
 Isotropic Kirchhoff PSDM
 Anisotropic Kirchhoff PSDM
 Scan RMO curves to detect Thomsen weak anisotropy parameters
epsilon and delta
 Linear or nonlinear moveout equation approximations PSDM
 Apply bound constraints on epsilon and delta
 Interpolate delta and epsilon between wells
 Linear, cubic, cosine, spline, CatmullRom spline, floor, ceiling, and nearestneighbor interpolation methods PSDM
Intuitive Graphical User Interface
 Multidimensional data viewer: synchronously scroll through up to 9 dimensions volumes
 Simultaneously view and interactively edit semblance picks on semblance volumes and RMS epsilon and delta picks on RMS epsilon and delta curves
 Edit multiple RMS epsilon and delta pick files simultaneously
 View interval epsilon, delta, and eta depth curves
 Visualize and edit picks and bound constraints on epsilon, delta, and RMO
 Visualize data geometry, image geometry, traveltime geometry, and velocity model geometry
 SEG Y viewer for input data QC, header, and trace investigation
 Data viewer for 2D/3D velocity models, traveltimes, gathers, and image
Accounting for anisotropy is essential
 To focus and improve resolution of PSDM images
 To improve the accuracy of spatial positioning of reflectors and correct depth misties
 To reduce interpretation uncertainty and drilling costs/li>
 For wide azimuth data
 For anisotropic AVO or AVAz analysis
 For large offset data
 To flatten nonhyperbolic moveout in the far offsets while benefitting from the increased illumination, fold, and signaltonoise ratio of longspread acquisition
 For multicomponent data
 For convertedwave surveys
 For accurate subsurface characterization: lithology, fracture orientation, and stresses
 For subsalt targets and shale plays
 64bit, for x6486 architecture processors (also known as x64, x64_86, AMD64, EMT64T, Intel 64)
 Red Hat® Enterprise Linux® (or compatible) 4.8 and above, 5.3 and above, 6.0 and above