Page 189 - Shale Shakers Drilling Fluid Systems

172 SHALE SHAKERS AND DRILLING FLUID SYSTEMS

How to determine cut point curves:

Feed:
1. Calibrate the pump circulating drilling fluid in the borehole.
2. Determine the flow rate in well.

Throughout Screen Sample:
1. Weigh the bucket.
2. Collect a representative sample of drilling fluid passing through the shale shaker screen.
3. Weigh the bucket and drilling fluid sample.
4. Calculate the weight of drilling fluid in the sample.
5. Calculate the volume of drilling fluid in the bucket (divide weight of drilling fluid in bucket by density of drilling fluid).
6. Calculate the flow rate of the sample passing through the shaker screen (subtract well flow rate from the discard
flow rate).
7. Calculate the time (in minutes) during which the volume in the bucket was collected (divide volume of drilling
fluid in bucket by sample flow rate).
8. Determine the weight of dry solids captured on each size screen.
9. Divide each weight of dry solids by the time required for these solids to pass through the screen.

Discard:
10. Weigh the trough that will be used to collect the shaker discard.
11. Measure the time (in minutes) required to collect all of the shale shaker discard in the trough.
12. Weigh the discard and trough.
13. Determine the weight of discard in the trough (subtract weight of the trough from the combined weight of the
trough and discard).
14. Sieve the discard sample through a stack of standard screens using the same screens, or the same sizes, used for
the feed sample.
15. Determine the dry weight of the sample on each standard screen.
16. Divide the dry sample weight by the time required to collect the sample (this is the mass discard rate).
17. Sieve the drilling fluid sample through a stack of standard screens.
18. Determine the weight of dry solids captured on each size screen.

Plotting the Cut Point Curve:
For each screen size in the standard sieve stack, the mass discard rate is divided by the mass feed rate. This ratio, mul-
tiplied by 100, is plotted on the "Y" axis of a graph, and the sieve size range is plotted on the "X" axis.