Solids control is a technique used in a drilling rig to separate the solids in the drilling fluids that are crushed by the drill bits and carried out of the well surface. Normally, a solid control system contains five stages: the mud tank, shale shaker, vacuum degasser, desander, desilter, and centrifuge. The shale shaker is used to separate big solids with diameter above 75μm, the desander addresses solids from 45-74μm , and the desilter segregates solids between 15-44μm. Sometimes the desander and desilter are combined as one high efficiency mud cleaner. When air enters the drilling fluids, a vacuum degasser is used to separate the air. When there is no air in the mud, the degasser works as a big agitator. All these stages are mounted on the top of the mud tank. After separating the solids, the clean mud can be pumped into the borehole again.
Drilling fluid maintenance cost, clean up, and 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 19th century when open earthen pits were used to separate the cuttings from the borehole. This was accomplished by a series of weirs and settling pits that allowed the solids to naturally settle out by using gravity. The clean mud then flowed into a suction pit to be re-pumped down the hole. This was the first solids control technique ever used.
The next innovation in solids control came when the shale shaker was introduced in the early 1930s for 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 1930s was the cone classifier or hydrocyclone. The basic principle of this device involves the centripetal 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. In an addition to shakers and hydrocyclones, the use of a high-speed centrifuge has significantly contributed to the ability of a drilling operation to reduce the amount of mud to be built and diesel/barite additions to maintain optimum low and high gravity solids proportions.
Recent advances in solids control include the creation of a closed loop system which allows for increased environmental control and reduction in the potential for spills of drilling fluids. Several US states have either passed or are considering the implementation of closed loop systems, particularly for hydro-fracturing operations.
The most famous solids control system manufactuer are almost from US, including: Derrick Equipment Company, MI Swaco Solids Control Company, NOV Brandt Solids Control Company, KEMTRON Technologies and Discovery Group USA.
- Fluids processing system
- Shale shaker The shale shaker is the first stage of solids control equipment in the fluids processing system,which removes cuttings with diameter above 75μm from the drilling fluids brought up from the wells.Afterwards,the treated fluids flow into the tank waiting to be processed again in the next stage of the system.
- Desander Desander is the second stage of solids control equipment.It is mainly used to take away the solids with diameter ranging from 45 to 74 μm from the formerly treated fluids and then send them to the next stage for more purification.
- Desilter Desilter is the third stage of solids control equipment.In this case,the solids with diameter ranging from 15 to 44 μm are to be separated from the rest,which will go through further processing.
- Mud cleaner
- Mud Gas Separator
- Centrifugal pump
- Jet mud mixer
- Mud agitator
- Electric ignition device
- Mud Gun
- Mud tank