On a rig, mud does a lot more than land on your coveralls. The mud that circulates through a well bore is instrumental to oil and gas drilling.
In last week’s blog post, we gave you a look at a day in the life of a Derrickhand. The Derrickhand’s responsibilities include maintaining the rig’s mud systems and mud properties. This week, we want to give newcomers to the drilling business a guide to the sophisticated world of mud!
What role does mud play in the drilling process?
When a hole is being drilled, drilling fluids or “mud” is circulated through the well bore. This mud performs many functions including:
- Bringing “cuttings” to the surface (cuttings are fragments of rock dislodged by the bit)
- Cooling and lubricating the drill bit
- Controlling pressure
- Stabilizing the hole
What is ‘mixing mud’?
When you were a kid, mixing mud meant sticking a garden hose into a bucket of dirt. In the drilling world, mud is made up of fluids (such as water or oil) and other mud-making materials (such as dry chemicals). The composition of the mud is mixed to specifications that fit the formation being drilled.
What are the components of a rig’s mud system?
Here are descriptions of some of the equipment used to circulate and monitor drilling fluid or mud:
Mud pump: A large, high-pressure reciprocating pump used to circulate the mud on a drilling rig.
Mud tanks (or mud pits): A mud tank is an open steel tank used for holding drilling fluids. Some mud tanks are used for suction to the mud pumps, settling of mud sediments and storage of reserve mud. Drilling mud is circulated through a series of open tanks to remove sand and fine sediments.
Kicker hose: A high-pressure rubber hose that connects the mud pump discharge line to the mud line.
Mud line: A high-pressure steel line that mud flows through from the kicker hose to the stand pipe (the stand pipe goes up the side of the derrick).
Shale shaker: A vibrating screen unit that is used to separate cuttings from the circulating fluid coming out of the wellbore. The separated cuttings vibrate over the end of the shakers to a shale bin, and the drilling mud falls back into the mud tanks.
Mud-density scale: A scale used to measure the density of the drilling fluid. Mud weight or mud density is directly related to the amount of pressure the column of drilling mud exerts at the bottom of the hole. The measurement is in pounds per gallon, pounds per cubic foot or kilograms per cubic metre.
Pit-level indicator: One of a series of devices that continuously monitors the level of drilling mud in the mud tanks. If the mud level drops too low or rises too high, the alarm may sound to warn the Driller of lost circulation or a kick.
Hopper: A large funnel mounted in the mud tank circulating system into which dry chemicals can be poured to mix uniformly with the drilling mud.
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Want to learn more rig lingo? Check out other posts in our “Rig speak 101” series: