Rock physics

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The science of Rock Physics allows the geoscientist to create and model the associations between the reservoir rock properties and the elastic properties of the geology derived from the seismic – (Velocity & Density information – Vp, Vs & Rho & and generated attributes such as Acoustic Impedance, Youngs Modulus, Poisson’s ration – LambdaMuRho.

The Rock Physics workflow gives a complete overview of the well log data at each well. Logs are initially subject to quality control with visual QC and cross-plot QC with bad data edited out. Edited logs are carried forward into fluid substitution to brine conditions and well log data is compared with standard Rock Physics models such as the Greenberg-Castagna Vp-Vs relationships in a multi-well analysis.

The locally calibrated derived trends from the multi-well analysis are used to model missing sections of log data, fluid substitution is applied to model the log data at oil and gas conditions and elastic attributes are compared to identify the best technique for fluid and lithology discrimination.

This workflow requires an understanding of the fluid properties at the well, elastic properties of the shale and the Petrophysical cut-offs that identify viable reservoir intervals.

By forward modelling, a prediction of the elastic properties of these lithologies can be made in areas away from direct well control – where actual data is sparse. Comparisons between the modelled simulation and seismic response can then be made as various fluid simulations are trialled to find the best-fit scenario.