Abstract: An improved instrument for measuring the relative "stickiness" of a drilling mud under well drilling condition is disclosed. It features a filtration member comprised of the material of the formation within which the well is drilled. After formation of a filter cake on the surface of the stone filtration member, a plunger is juxtaposed to the stone filtration member and the amount of torque required to rotate the plunger with respect thereto after juxtaposition for a fixed period of time is measured, to provide a relative indication of the adhesion of the plunger to the stone.

Abstract: A deviated borehole is drilled with a rotary drilling technique in which the drill string is vibrated at a suitable frequency and amplitude to reduce the friction of the drill string against the lower side of the borehole and to promote the free movement of the drill string therein.

Abstract: This specification discloses a system and method for flushing and cleaning a hydrocyclone used in removing drilled solids from a drilling mud circulated in the drilling of a borehole. The system is comprised of a feed pump connected via a mud conduit to the inlet of a hydrocyclone. A check valve is located in the mud conduit intermediate the feed pump and the inlet of the hydrocyclone which allows the mud to flow through the mud conduit only in the direction toward the hydrocyclone. Another conduit for flowing a cleaning liquid is connected with the mud conduit on the hydrocyclone side of the check valve. A valve responsive to a signal, pressure or electrical, is located in this other conduit intermediate the mud conduit and a supply of cleaning liquid.