Sweep is a mud which has higher rheology and/or more mud weight than current mud property. It is used to carry cutting that set at low side of a wellbore and it is widely used for Sea water drilling.
These illustration show how sweep works.
Cutting at the low side of the well bore (image below)
Sweep is pumped (image below).
Hole is clean (image below).
Note: In reality, the pipe is not in the exact center of the well but these illustrations are used to aid the understanding of how sweeps works.
This is a real case which will show you how the sweep helps hole cleaning.
Drilling fluid – sea water
Funnel Viscosity +/- 100 sec
PV = 25
YP = 34
Density = 10.0 ppg
Hole angle = 59 degree
Sweep volume = 50 bbl
Formation = sand stone, clay stone, clay, trace carbonate
Drilling parameters before pumping sweep
Pick up = 300 klb
Rotate weight = 250 klb
Slack off = 200 klb
Torque = 23,000 ft-lb
Drilling parameters after pumping sweep
Pick up = 280 klb
Rotate weight = 230 klb
Slack off = 190 klb
Torque = 20,000 ft-lb
It is clearly seen that sweeping the hole helps hole cleaning.
Before (Image below)
After (Image below)
Do you have any experience about pumping sweep?
Please feel free to share with us in the comment section.