Oil Well Drilling mud pits

MUD PITS

Mud pits are required for holding an excess volume of drilling mud at the surface. This surface
volume  allows  time  for  settling  of  the  finer  rock  cuttings  and  for  release  of  entrained  gas
bubbles  not  mechanically separated.  Also,  in  case  some  drilling  fluid  is  lost  to  underground
formations, this fluid loss is replaced by mud from the surface pits. The settling and suction pits
sometimes are dug in the earth with a bulldozer but more commonly are made of steel. Mud pit
compartments are also called shaker pits, settling pits, and suction pits, depending on their main
purpose.. A large earthen reserve pit is provided for contaminated or discarded drilling fluid and
for rock cuttings. This pit also used to contain any formation fluids produced during drilling and
well testing operations. mud pit usually lined with a single-ply 20 or 30 milmeter polyethylene
.liners that resist punctures and wind damage to prevent any contamination


Dry mud additives often are stored in sacks, which are added manually to the suction pit using
mud mixing hoppers. However, on many modern rigs bulk storage is used and mud mixing is
largely automated. Liquid additives can be added to the suction pit from chemical tank. Mud
.jets or motor-driven agitators often are mounted on the pit for auxiliary mixing

THE CONTAMINAT-REMOVING EQUIPMENT

This  equipment  includes  mechanical  devices  for  removing  solids  and  gases  from  mud.  The
coarse  rock  cuttings  and  cavings  are  removed  by  the  shale  shakers,  the  shale  shaker  is
composed of one or more vibrating screens over which mud passes as it returns from the hole
The risk in shale shakers is that gas may be present in vicinity of shale shaker leading to a a
.probable explosion or toxicity

Multiple shakers may be used

In parallel for high flow rate - 

In series for multiple filtering range - 

When  the  amount  of  finely  ground  solids  becomes  too  great,  they  can  be  removed  by
hydrocyclone  and  decanting  centrifuges  also  called  (desander).  A  hydrocyclone  is  a  cone-
shaped housing that imparts a whirling fluid motion much like a tornado. The heavier solids in
the mud are thrown to the housing of the hydrocyclone and fall through the apex at the bottom
.Most of the liquis and lighter particles exit through the vortex finder at the top

The decanting centrifuge (desilter) consists of rotating cone-shaped drum which has a screw
conveyor attached to its interior . rotation of the cone creates a centrifugal force that throws the
heavier particles to the outer housing. The screw conveyor moves the separated particles to the
discharge

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