The Permeability of Rock Salts

by Nelson Cole

At the University of Texas they found Rock Salts to be more permeable than originally expected. It was known that salt generally blocks fluid at a shallow depth. This feature of salt allows reservoirs to form. However, scientist had contemplated that salt may be permeable at a greater depth. When setting out to conduct experiments University of Texas, professors originally thought that Rock Salt would be used as a hydrocarbon seal for the oil industry. Since salt generally blocks fluid at a shallow depth and allows it to flow at a greater depth. It was quickly confirmed that salt becomes permeable at a greater depth. The real surprise came in that the fluids were sometimes able to flow through the salt at a shallow depth. The findings could have important implications for nuclear waste storage. Previous work on the permeability of salts has focused on the cracks formed by the nuclear waste itself. The findings from the study show that undisturbed rock salt can be permeable as well and it is permeable because of deformation.

Deformation of the rock salt is what causes the tiny isolated pockets of brine between salt crystals to stretch, when stretched it allows liquids to move. The next question is how much water can flow through rock salt that is free from mining activity and what may cause rock salt to deform?

In New Mexico currently low level nuclear waste is stored in salt beds beneath the ground. While high level nuclear waste is stored in power plants, pool or dry casks. These are all only temporary solutions for handling the storage of high level waste. While there has been a proposal for decades to store the high level waste in the Yucca Mountains in Nevada it has been stalled because of political and regulatory hurdles. The findings from scientist at the University of Texas in Austin prove timely because it offers a very viable solution for storing high level waste.

University of Texas Cockrell School of Engineering

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