WANG, YU-HUI, SU-MIN WANG, SHU-HUA LIAO, ZHI-CHAO MAO, and CHUAN-REN CHEN, Jianghan Petroleum Inst., Department of Basic Sciences, Jiangling, Hubei, P.R. China

ABSTRACT: Regular Fractal Islands on Rock-pore Interface in Sandstone

The fractal behavior of the pore space of sedimentary rocks observed by recent experiments such as isothermal adsorption, small-angle adsorption and STM are only statistically self-similiar or self-affine. Recently we found by STM widespread triangular porous clusters with nest structure developing on the cements and pore-fillings in the sandstone fracture surface. The morphology of the clusters are similiar to that of the fractal structure named Sierpinskian sponge (skewed web), both have triangular pores and nest structure scaled down by a factor of 1/2. The arrangement of the triangular porous clusters is not as good as that of the Sierpinskian sponge, so we call them Quasi-Sierpinskian Sponge (QSS). This structure presents strong evidence for the existence of fractal pore space in sedimentary rocks. Further analysis shows that QSS is an volume fractal island on rock-pore interface, which is essentially different from the volume fractal structure of original pores and the surface fractal of rough pore walls. The mechanism for the genaration of QSS may be preferential dissolution of cements and pore fillings in sandstones instead of spontaneous surface roughening or diffusion-limited aggregation. And the difference between global and local fractal behavior suggests that multi-fractal and multi-scale fractal theory may be required to describe the structure of pore space in sandstone.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.