These LSRV fluids have been widely used because of of their carrying capacity and solids suspension ability. They have been accepted as a way to minimize cuttings bed formation in high angle and horizontal wells, and as a way to reduce barite sag in high weight muds. Recent studies and field experience indicate that his LSRV is helpful in controlling the invasion of drilling fluids and filtrate by creating a high resistance to movement into the formation openings. 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.