Experimental investigations of the flow of water and some water solutions in sandstones

Abstract

Clay present in sandstones is sensitive to the water saturation and to the kind of ions and their concentration in the flowing water. The reaction of the rock upon these factors manifests itself as an internal swelling or internal shrinkage of the rock and the resulting permeability changes in the water flow.

This paper describes experimental investigations into permeability changes occuring in the flow of water and water solutions of salt of various concentrations in sandstones collected from oil reservoirs and from hard coal mines. Experiments with the flow of water and of solutions in coal are also mentioned.

Increasing the water content in sandstones from an air-dry condition to the state of full saturation results in rapid (within hours or days) internal swelling of the rock leading to a decrease in permeability which can achieve two or three orders of magnitude. In the flows of water solutions of salt in sandstones it is possible to produce changes in permeability (increase or decrease) even by two orders of magnitude by means of changing the concentration or the ion composition of the solution.

The flow of a diluted solution of calcium hydroxide proved to be very effective in increasing permeability. Big effects were obtained even when using low concentrations of this solution, which suggests the possibility of a practical application for the observed phenomena.