Statistical network theory of silica deposition and dissolution in diatomite

One area of concern accompanying steam injection into siliceous diatomite i s the evolution of permeability and porosity as silica dissolves in hot ste am condensate and is redistributed on rock surfaces as condensate cools. We employ a network model to gauge how evolving pore topology affects permeab ility and porosity. The model is anchored to real rock through measured por e-throat and pore-body size distributions. Macroscopic trends are correlate d in terms of network connectivity and pore body to throat aspect ratio. When porosity change from 0 to 10% is examined closely, it is found that pe rmeability decrease correlates with porosity decrease according to a power- law expression with power-law exponents in the range of 8 to 9. Such a powe r-law dependence has been measured previously by experiment(1). These value s confirm the strong dependence of permeability on deposited silica. The di ssolution process displays an equally strong dependence on porosity change, and again, permeability increases most dramatically for dissolution in net works with small values of connectivity and large values of the pore-body t o pore-throat aspect ratio. Power-law expressions adequately describe perme ability increase as a function of porosity for a moderate range of dissolut ion.