f Rock properties - The missing link in exploitation and exploration

Relationships between different physical properties of rock permit one to interpret log, seismic, magnetic and gravity data. One relies upon these correlations to infer subsurface properties. To map lithology, porosity, or permeability, for example, one must employ a technique which has sensitivity to the property of interest. These techniques generally produce a one, two, or three dimensional image of some attribute say vetocity or amplitude. Beyond a knowledge of the, physics behind a technique, one must establish the correlation between the attribute mapped and the property desired. In many circumstances these properties can not be linked to the attribute in an ab inito sense. Thus healthy empiricism is required to form the bridge. A case in point, the classical theories of Biot (1956a,b) and Gassmann (1951) require the definition of a porous frame modulus, this for obvious reasons can not be derived from first principles without a priori knowledge. However, once the modulus is defined, the theory permits one to conveniently calculate the influence of various saturants on velocity. Such information is extremely useful in modeling an AVO response, for example. The problems hampering such empiricism to date have been twofold: first, the cost on a per sample basis has been prohibitive and second, the core to be characterized has suffered irreversible degradation. GEM (Geophysical Evaluation Modules) has eliminated both these restrictions. Because GEM is portable, it can be brought to a well site or Gore facility and fresh samples can be characterized. Secondly, because of the high degree of automation and parallel processing concepts, the cost for a rather extensive suite of measurements has been reduced by an order of magnitude.