thumb|Three deck shale shaker, part of a solids control system
'''Solids control''' is a process used in drilling rigs which use drilling fluid. It involves separating the "cuttings" (drilled material) from the fluid, allowing it to be recirculated or discharged to the environment.<ref name="Shaker screens">{{cite web |title=Solids control system for oil rig during well drillings |url=https://shakerscreens.org/solids-control-equipment/solids-control-system-oil-drilling-rigs.html |website=Shaker screens |access-date=6 March 2021 |date=14 April 2016}}</ref>
==Background== Drilling rigs are drilling systems for creating boreholes in the ground. They use drilling fluid (also known as drilling mud) as lubricant and coolant for the drill bit and to clear the cuttings out of the hole. The drilling fluid needs to have the cuttings removed before being recirculated or discharged, which is achieved by the solids control system attached to the rig.<ref name="Netwas Group">{{cite web |last1=Price |first1=Donald |title=The Functions Of Drilling Muds - Well Control |url=https://www.netwasgroup.us/well-control-2/the-functions-of-drilling-muds.html |website=Netwas Group Oil |access-date=6 March 2021 |language=en |date=2 February 2021}}</ref><ref name="Shaker screens" />
==Operation== Solids control systems consist of several stages of treatment, removing progressively finer particles from the drilling fluid.
===Screen separation=== The principle of screen separation is to pass the drilling fluid over the screens with different size holes, allowing fluid and small particles to pass through while separating larger particles. It is used to filter large solids out of the drilling mud, typically with particle sizes above 75μm.<ref name="Shaker screens" /> The machines that use this principle are called shale shakers, and consist of a series of vibrating screens that the mud passes over. When working effectively these machines can remove up to 80% of the cuttings from the drilling fluid.<ref name="Drilling course">{{cite web |title=Solid Control Equipment |url=https://www.drillingcourse.com/2021/01/solid-control-equipment.html |website=Drilling Course |access-date=6 March 2021}}</ref>
===Settling separation=== Settling separation relies on gravity to draw solid particles down through the fluid in vessels called ''mud pits'' or ''silt pits''. The fluid flow rate is reduced, allowing the particles to drift down while the clean fluid is drawn off.<ref name="Drilling course" /> This stage of separation deals with particle sizes between 15μm and 74μm.<ref name="Shaker screens" />
===Forced separation=== Forced separation relies on perceived centrifugal force pushing solid particles to the outside of a rotating body of fluid. Machines that use this principle include centrifuges and hydrocyclones. The drilling fluid is injected into a cone-shaped vessel at high pressure, allowing the clean fluid to be drawn off from the top of the chamber.<ref name="Drilling course" /> An alternate design relies on a rapidly rotating drum, which flings the solids in the drilling fluid to the outside of the cylinder to be drawn off as a thick sludge.<ref name="SCS">{{cite web |title=Drilling Fluid Centrifuge Work Principle in Mud System – Solids Control System,Drilling Waste Management,Drilling Fluids Treatment |url=http://www.solidscontrolsystem.com/drilling-fluid-centrifuge-work-principle-in-mud-system/ |website=www.solidscontrolsystem.com |access-date=6 March 2021}}</ref>
===Gas separation=== Sometimes gas can get into the drilling fluid from the rock that the borehole passes through. This can reduce the density of the fluid, causing structural issues in the well.<ref name="Well control">{{cite web |title=Introduction to Well Control |url=https://www.drillingcourse.com/2016/01/introduction-to-well-control.html |website=Drilling Course |access-date=6 March 2021}}</ref> A vacuum is applied to remove the gas from the fluid, then vented or flared off.<ref name="Drilling course" />
==References== {{reflist}}
Category:Drilling technology Category:Drilling fluid