Page 192 - Shale Shakers Drilling Fluid Systems
P. 192
CALCULATING DRILLED SOLIDS CONCENTRATIONS 175
Calculation procedure:
A sample of the discard is placed in the pycnometer and weighed: Pyc. + Sample weight = 898.68 gm
Since the pycnometer weighs 660.61 gm dry and empty, the sample weight is 209.07 gm
The pycnometer with the shaker discard sample is filled with distilled water, pressurized, and weighed:
Pycnometer + Sample + Water = 925.73 gm
The weight of water added is: 925,73 gm - 896.68 gm = 56.05 gm; the volume of water added = 56.05 cc
Since the pycnometer volume is 173.91 cc, the sample volume is: 173.91 cc - 56.05 cc = 117.86 cc
The density of the sample is 209.07 gm/117.86 cc = 1.77 gm/cc; the volume of water added = 56.05 cc
Since the pycnometer volume is 173.91 cc, the sample volume is: 173.91 cc - 56.05 cc = 117.86 cc
The density of the sample is: 209.07 gm/117.86 cc = 1.77 gm/cc
volume of the shale sample. Because the volume To determine the quantity of drilled solids dis-
of the shale sample and the weight are known, the carded by the shale shaker, a sample of the
density may now be calculated as 2.47 gm/cc. discarded material is placed in a metal dish and
After movement of the solids across the shale dried in an oven overnight. The weight percent
shaker screen appears relatively uniform for more of dry solids is 68.11% wt. and has a density of
than 10 minutes, all of the shaker discard is col- 2.78 gm/cc.
lected in a bucket. In 16.21 seconds, 3720.7 gms The rate of dry solids discarded is calcu-
of discard is captured. The discard rate is 13,772 lated from the product of the wet discharge
gm/min. and the discard has a density of 1.774 flowrate and the weight fraction of dry solids in
gm/cc or 14.8 ppg. the discharge (with the appropriate unit conver-
The objective of the shale shaker is to remove sion factors):
drilled solids, preferably with limited amounts of
drilling fluid. The fraction of the discard stream
Rate of Dry = (13,772 gpm)(0.6811)
that is water, barite, and low-gravity solids can be
Solids Discard x (1.0 lb/453.59 gm)
determined by the equations presented above. x (60 min/hr)
These calculations indicate that the discard stream
contains 5.06% volume barite, 38.38% volume low-
gravity solids, and 56.56% volume water. = 1,239 Ib/hr
Calculation procedure to determine discarded low-gravity solids:
The discard from the screen weighs 14.8 ppg and contains 43.44% volume solids. The equation presented in the sample
calculation is:
(p B - P|g)V lg = 100 Pf + (p B - Pf)V s - 12MW
Assuming a barite density of 4.2 gm/cc and 2.47 gm/cc for drilled solids, the equation becomes:
(4.2 - 2.47)V |g = 100 + (4.2 - 1.0X43.44) - 12(14.8)
V lg = 38.38% volume
