A laboratory study on the borehole-stabilizing property of sillcate drilling fluids

The borehole-stabilizing property of silicate-based drilling muds is investigated by means of shale recovery (SR) and shale stabilization index(SSI) tests. It is shown that the optimum moduli of silicates to be used are in range 2. 8-3.2 and the preferable feeding quantities in muds are 2-5%. The higher the atomic ratio of Na to K in silicates the higher the SR value in basic muds is obtained but ratio Na/K has little effect on SR values in the muds containing KCl. Salts synergically enhance the borehole-stabilizing capacity of the silicate-based muds while Ca 2+ badly influence the mud rheology. Organic additives change borehole-stabilizing capacity slightly mainly by the way of changing rheologic and filtration properties.