Solids control is a process used in

drilling rigs A drilling rig is an integrated system that Drilling, drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to ...

which use

drilling fluid In geotechnical engineering, drilling fluid, also known as drilling mud, is used to aid the drilling of boreholes into the earth. Used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also use ...

. It involves separating the "cuttings" (drilled material) from the fluid, allowing it to be recirculated or discharged to the environment.

Background

Drilling rigs are drilling systems for creating

boreholes A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petr ...

in the ground. They use drilling fluid (also known as drilling mud) as

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

and

coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corr ...

for the

drill bit A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In orde ...

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.

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 75

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

. The machines that use this principle are called

shale shakers Shale shakers are components of drilling equipment used in many industries, such as coal cleaning, mining, oil and gas drilling.They are the first phase of a solids control system on a drilling rig, and are used to remove large solids (Drill cutt ...

, 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.

Settling separation

Settling separation relies on

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

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. This stage of separation deals with particle sizes between 15μm and 74μm.

Forced separation

Forced separation relies on perceived

centrifugal force Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...

pushing solid particles to the outside of a rotating body of fluid. Machines that use this principle include

centrifuges A centrifuge is a device that uses centrifugal force to subject a specimen to a specified constant force - for example, to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby s ...

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. 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 Sludge (possibly , or some dialect related to slush) is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. It can be produced as a settled sus ...

Gas separation

Sometimes

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

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. A vacuum is applied to remove the gas from the fluid, then vented or flared off.

References

{{reflist Drilling technology Drilling fluid