Influence of potassium concentration the swelling and compaction ofmixed (Na, K) ion-exchanged montmorillonite

A B S T R A C T: Oedometer swelling and compaction tests up to a maximum pressure of32 bars were made on the Wyoming montmorillonite SWy-1 with a range of mixed (Na,K) exchange ion compositions. The permeabilities and water diffusivities of the compacted clays were calculated using soil physics theory. Significant inhibition of swelling from that of the Na-montmorillonite is developed for K fractions inthe range 0.30 < K + < 0.56. However, the water diffusivity increases by a factor of approximately sixas the K exchange fraction increases from 0 to 0-7. Permeabilities to water flow show a power-law dependence onthe void ratio e. XRD measurements at controlled humidity ield equilibrium interlayer spacings which in general increase with both increasing relative humidity and increasing Na exchange fraction. The extent of swelling is strongly inhibited in clays having Na exchange fractions of 0.44 or less, in good agreement with the oedometer studies. Potassium electrolytes, normally KOH or KC1, have found widespread use in petroleum engineering as components of inhibitive water-based drilling fluids designed for the control of borehole gauge in chemically active fine grained argillaceous rocks such as shales and mudstones. Such electrolytes (usually in conjunction with anionic polymers) are known t