Since the fluid moves at a very slow rate, viscosity becomes very high, and the resulting resistance to flow allows the drilling fluid to be contained within the borehole with a very slight penetration. This has been beneficial in protecting the zones from damage as well as reducing differential sticking in these fluids. Lost circulation is also a severe problem in rotary drilling. Lost circulation occurs when the differential pressure of the hydrostatic column is much greater than formation pressure, the openings in the rock are able to accept and store drilling fluid so that none is returned to the surface for recirculation. The fluid is lost downhole and becomes an expensive and dangerous problem.
Lost circulation can lead to hole instability, stuck drill pipe, and loss of well control.
At the least, it halts drilling operations and requires expensive replacement volume to be used. These are usually fibrous, granular, or flake materials such as cane fibers, wood fibers, cottonseed hulls, nut hulls, mica, cellophane, and many other materials. These LCM materials are added to the fluid system so that they may begin to build and seal. These LCM materials themselves are damaging to the zones, and because they many times must be carried in the drilling fluid to maintain circulation, solids removal is halted and high solids mud results. A new technique of aiding in severe lost circulation control involves introducing a blend of surfactants to a fluid system which has the ability to form bubbles.