Drilling fluid maintenance cost, clean up & disposal cost as well as the overall cost of boring, can be reduced dramatically when proper solids control techniques are utilized. These facts were recognized in the oil industry in the late 1800's, when open earthen pits we used to separate the cuttings from the borehole. This was accomplished by a series of weirs and settling pits that allowed the solids to settle out naturally by using gravity. The clean mud then flowed into a suction pit to be pumped back down the hole. This was the first solids control technique ever used.
The next innovation in solids control came when the shale shakers were introduced in the early 1930's in the oil industry. The shale shakers were derived from technology used in the mining industry. The shale shaker remains today the primary piece of solids control equipment utilized in the industry.
Another machine borrowed from the mining industry in the 1930's was the cone classifier or hydrocyclone. The basic principle of this device involves the centrifugal forces brought about by the high velocity of the drilling fluid spinning in the cone forcing the larger and heavier solids to settle outward toward the cyclone wall and downward toward the underflow solids discharge. Together with the shale shaker hydrocyclones have become an integral part of today's solid control system.
The future path of solids control systems will continue to increase the overall removal efficiency of undesirable solids from the drilling fluid. This will include continued improvements in shale shakers and screen life. Research investigating alternate technology such as using vacuum techniques and different motions may prove more effective in the future. The continuing trend of more stringent environmental regulations around the world will require more and more solids control systems to be implemented to minimize haul off of drilling waste not to mention the cost saving on equipment such as mud pumps and mud motors.