Solids control refers to a well drilling technique used to provide drilling fluid to deep well drilling rigs and to clean this fluid for further use. The technique is often called mud drilling because it uses a flow of water and mud to bring solids out of bore holes and cool the drilling rig equipment. This drilling fluid also facilitates the necessary hydrostatic pressure to prevent the influx of natural formation fluids into the bore hole. This technique has increased the safety of the well drilling process while making explorative drilling a cost-effective option.
The well drilling processes and methods of solids control have seen a variety of evolutions over time. From simple gravity controlled solids removal pits to complex mechanical solids control systems, the various techniques and equipment used to remove solids from drilling fluid have made mud drilling possible. With the creation of solids control measures, bore drilling has become far more economical as the drilling solution is reused.
One of the earliest known uses of solids control in a well drilling process that occurred in the late 19th century. A series of processing pits were used to capture the drilling fluid from well drilling rigs. As the fluid passed from one pit to the next, it was allowed to settle. The force of gravity caused the solids to settle out of the liquid. The drilling fluid could then be channeled to a pumping station where it was sent on to the drilling equipment for re-use.
This early system of solids control was used as the primary method until the invention of shale shaker in the 1930s. The shale shaker uses a series of progressively smaller screens to filter out cut materials from drilling fluid. Operating on the same principle as the sorting machines used the gravel mining industry, the shale shaker removes debris from drilling fluid using gravity and vibration. As the drilling mud passes over the shaker table, the vibrations cause the larger cuttings to shake out of the solution.
The shale shaker is often paired with another piece of mining equipment called the hydrocyclone. The hyrdrocyclone is used in the solids control process to filter drilling fluids by centrifugal force. By creating a swirling vortex of drilling fluid inside the hydrocyclone, the solid matter created by the drilling process is forced to the outer walls of the machine. These solids then slide down to the discharge chute of the machine while the cleaned drilling fluid is pumped back to the drilling equipment.