Relating Thin Sections to Permeability, Mercury Porosimetry, Formation Factor, and Tortousity

C. A. McCreesh, E. L. Etris, D. S. Brumfield, R. Ehrlich

The efficiency of reservoir rocks and the integrity of reservoir seals are controlled not by the amount of porosity present, but by the configuration of that porosity. Mercury injection curves, permeabilities, and values of Archie's formation factor are all related to this configuration, and so are used in determination of reservoir quality. They cannot be simple functions of porosity because porosity represents aggregate pore volume, and fluid movement is controlled by the size of pore throats. However, quantitative analysis of the patterns of porosity exposed in thin sections, coupled with any one of those three physical measurements on related plugs, is sufficient to establish the relationship between pore type and throat size. Once determined, the other physical prope ties can be derived using simple physical relationships. Thus, from a set of thin sections and associated permeability values, mercury injection curves and inert (no CEC) formation factors can be derived. The degree of flow tortuosity in the plug can also be determined from the same data. Unbiased estimates of size, sorting, and packing can also be derived from the section, linking the physical data to depositional fabric and so allowing spatial extrapolation of the physical data by use of depositional models.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.