Safe storage and effective monitoring of CO2 in depleted gas fields.

Carbon capture and storage (CCS) is vital to reduce CO(2) emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO(2) storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO(2) storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO(2).

Scaling of the spanning threshold in gradient percolation.

A simple and fast way to apply correlations in percolation simulations is to apply a uniform gradient to the occupancy probabilities. For small networks, exact results are presented here for the spanning thresholds in site percolation with a gradient for networks up to 4×4 in two dimensions and 2×2×2 in three dimensions. Numerical results are provided for larger networks that extrapolate to a linear modification of the threshold proportional to the gradient for moderate values of the gradient.

Trapping thresholds in invasion percolation.

We give numerical estimates for the site percolation trapping thresholds for invasion percolation on various three dimensional lattices. We find that in most cases the thresholds for invasion and ordinary percolation coincide. However, for coordination numbers less than five the thresholds diverge. Since most rock networks exhibit coordination numbers less than five the rules for simulating residual saturation in porous rocks must be chosen carefully.