Several publications over the last 20 years have established that black organic shales are generally characterized by strong velocity anisotropy, low velocity in the bedding-normal direction, and relatively low density and porosity (e.g., Vernik and Nur, 1992; Vernik and Liu, 1997). These rock properties are of interest in seismic attribute studies, but even more so in geomechanical applications related to reservoir characterization and hydraulic fracture stimulation. Organic shales typically, but not necessarily, express strong vertical transverse isotropy (VTI), with axis of symmetry perpendicular to the bedding-parallel lamination and clay-particle-preferred orientation. High-resolution SEM imaging (Figure 1) immediately reveals all these textural features in addition to silt grains and the lenticular distribution of the solid organic matter (kerogen), which in turn is characterized by significant intraparticle porosity in mature shales. Any TI medium is described by the five independent elastic constants ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) and detailed multidirectional ultrasonic core measurements can provide the most accurate means for their adequate evaluation. Single-well sonic- and density-log data fall short of the full TI tensor description resulting in major ambiguities related to empirical correlations.

Simulation to Seismic (Sim2Seis) is a forward modeling technique used to predict/generate synthetic seismic response from a static or dynamic reservoir model. There are two key components of a Sim2Seis workflow: reservoir model (geological and/or simulation model) and petro-elastic models (PEMs). PEMs are rock physics functions which relate reservoir properties such as rock types, porosity and fluid saturation to the elastic properties such as compressional and shear velocities, and density. Predicted elastic properties are used to compute reflection coefficients, when convolved with a wavelet generate a synthetic seismic volume (1D or 3D).There are several applications for Sim2Seis in reservoir characterization. It can be applied to test the consistency of a 3D geological static model, or of a history-matched simulation (dynamic) model with the actual seismic data. It can also be applied to study the impact of saturation change on seismic response (4D effect). A case study from an oil producing Tertiary age field in the North Sea was used to illustrate the applications of Sim2Seis workflow. This case study reveals the value of integrating the static and dynamic data for more accurate reservoir characterization, and consequently building a more reliable reservoir flow model which honors petrophysical and seismic data as well as production data.