Sand Traps

After the drilling fluid passes through the main shaker, it enters the mud pit system. When screens 80-mesh and coarser were routinely used, the sand trap performed a very useful function. Large, sand-size particles would settle and could be dumped overboard. The bottom of a sand trap

Weighed Mud Two-Stage Centrifuging

Gumbo Removal

Return To Hole

Addition section

Removal section

Send

Trap Screened Solids Dump Discard

Low Low

Suction & testing Section

LEoq im*

Adjustable

Equalizer normally.high.

\ < Adjustable

Equalizer

Solids Fluid Return• Return

Screened L__-1

Solids | Screen"

Discard » Underflow return

Fluid Return

"^Centrifuge

Figure 5.5. Weighted mud two-stage centrifuging.

Weighed Mud Single-Stage Centrifuging

Suction & testing Section

Gumbo Removal iff *

Send n

Trap

Dump

Weighed Mud Single-Stage Centrifuging

Gumbo Removal iff *

Send n

Trap

Dump

Sand Traps Rig

Screened Solids Discard

Figure 5.6. Weighted mud single-stage centrifuging.

Screened Solids Discard

Figure 5.6. Weighted mud single-stage centrifuging.

should be sloped at about 45°^to facilitate quick dumping. A sloped bottom 45° or greater will self-clean when dumped. The sand trap should not be agitated and should overflow into the next compartment. Linear and balanced elliptical motion shale shakers have all but eliminated this technique. Small drilled solids generally do not have sufficient residence time to settle. When inexpensive drilling fluid was used, sand traps were dumped once or twice per hour. Today, in the era of fine-mesh screens, expensive waste disposal, and environmental concerns, such dumping is either not allowed or is cost prohibitive.

The preceding illustrations show the solids-removal system with a sand trap. Rigs currently operating may or may not have sand traps. If a rig does not have a sand trap, then the shakers would have their underflow directed to the degasser suction pit and all other functions would remain as illustrated.

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