Abstract: The invention provides a method of enhancing the recovery of shale-containing cuttings during the drilling of a borehole in a shale-containing subterranean formation which comprises adding to the drilling fluid circulating in the borehole a finely ground, very sparingly soluble, anhydrous, alkali metal silicate glassy material to provide the drilling fluid with a concentration of soluble silica in the range from about 0.1% to about 1.0% by weight of the aqueous phase of the drilling fluid. Preferably the drilling fluid has a pH in the range from about 8.0 to about 11.0, most preferably about 8.5 to less than 11.0. The preferred alkali metal is potassium.

Abstract: An apparatus for and method of drying agglomerated moist particulate material, the particles of which when dry have a very low density. Drying is effected by supporting the material on a screen within a retainer, and by applying heat to the material in contact with the screen by way of an electrical or heat exchange type heating element. Vaporized moisture is extracted by way of a vent which extends upwardly through the retainer from a position adjacent the screen, so that the vapour is caused firstly to flow down through the screen and then upwardly through the vent.