CLAY ROCK SWELLING
The interaction of drillable rocks with drilling mud water phase is the important factor influenced the open borehole walls steadiness. Clay hydration is attended by its swelling and internal voltage growth in the hydrated rock volume leading to deformation, destruction, and finally dispersion of hydratable clay rock in the water phase of drilling mud. Clay rock swelling leads to the decay of disperse structure of drilling deposits, slide-rocks and collapses with the cavity formation, on the one hand, and to the narrowing of borehole as a result of plastic deformation and sticking, on the other hand. To register this phenomenon and to manage it during the process of borehole deepening it is necessary to define the parameters of anisotropy of swelling of drilling rocks. Clay and clay rock swelling together with drilling mud is the factor which should be taken into account for successful well-drilling.