PATTERN-FORMATION IN SEDIMENTARY-ROCKS - CONNECTIVITY, PERMEABILITY, AND SPATIAL CORRELATIONS

Sedimentary rocks have complicated permeability patterns arising from the geological processes that formed them. We concentrate on pattern f ormation in one particular geological process, avalanches (grain flow) in wind-blown or fluvial sands. We present a simple experiment and nu merical model of how these avalanches cause segregation in particle si ze that lead to characteristic laminated patterns. We also address the longstanding question of how such patterns are generated. We analyze data on two sandstone samples from different, bur similar, geological environments, and find that the permeability fluctuations display long -range power-law correlations characterized by an exponent H. For both samples, we find H approximate to 0.82-0.90. These permeability fluct uations significantly affect the flow of fluids through the rocks. We demonstrate this by investigating the influence of long-range correlat ion on percolation properties, like cluster morphology. We relate thes e properties to characteristics important for hydrocarbon recovery suc h as breakthrough time for injected fluids and recovery efficiency.