Rock Solid Images

Rock Physics Diagnostics & Pseudo Wells

Rock Physics Diagnostics can help us understand the behavior of the reservoir and non-reservoir zones and correct for some of the problems encountered in well log data (Avseth, et al., 2000). It is the process of finding a rock physics model that is consistent with the well and core data available. For example, we may find that some zones in the well are closely fitted with an unconsolidated sand model (Dvorkin and Nur, 1996) while other zones follow critical porosity (Nur, et al., 1998) or elliptical crack models (Kuster and Toksoz, 1974). These models may have adjustable parameters such as pore aspect ratio or critical porosity that can be determined empirically from the local data. Similarly some Vs prediction methods are best calibrated to local conditions if core Vp and Vs data or dipole shear wave logs are available. Rock physics calibrations can also aid in selecting a fluid mixture model such as homogeneous or patchy distribution (Dvorkin, et al., 1999). Well log data will also be compared to available lab data, for example Han, et al (1986) and to theoretical limits such as Hashin-Shtrikman bounds (1963).

The purpose of RPD is to allow reliable modeling and perturbation of seismic properties with changes in reservoir properties. For example, the data above shows P-wave impedance plotted versus total porosity. Superimposed on the data is a set of rock physics models with different clay fractions. For the data in question, there is a definite link between clay content and porosity. Therefore, if we wish to change porosity, then clay content must also be changed. The rock physics model allows for prediction of seismic properties away from the wellbore. See Rock Physics Diagnostic in a Sand/Shale Sequence - a paper presented at the 2003 SEG for more information on this topic.

Rock Physics Diagnostics in iMOSS