Abstract

The porosity of sandstones is commonly observed to decrease during burial. Such decrease is frequently treated as a function of burial depth, but depth is a position coordinate that may not reflect the time-temperature history by which all subsurface processes are influenced. An alternative approach that is adapted in this study is to consider porosity decrease during burial as a function of thermal maturity. Such an approach links porosity evolution in the subsurface and the maturation of kerogen and petroleum, in that the vitrinite-reflectance measurements used to define porosity trends can also be used to characterize petroleum generation and destruction.

Trends of porosity versus vitrinite reflectance (R_m) of the form f=AR_m^B (where B is a negative number), characterizing both typical and highest sandstone porosities, are derived from 131 measurement suites incorporating 4,353 individual porosity measurements. Diverse sandstone facies and geologic settings are represented, and the data span a maturity range of R_m=0.25-1.7%. The porosity-R_m data form trends which are projected to maturities as high as R_m=7% in order to speculate upon the distribution of sandstone porosities in the very deep (mature) portions of sedimentary basins.