Shale shakers are components of the solids control systems. Shale shaker mainly used in the oil and gas drilling industry. Shale shaker is the first phase of a solids control system on a drilling rig, and are used to remove large solids (cuttings) from the drilling fluid (“mud”).
Solids control may be defined as the control of the quantity and quality of suspended solids in the drilling fluid so as to reduce the total well cost.
The drilling cuttings removal equipment is often called solid-control equipment because it is mostly used for removing drilling cuttings in the mud returned from the borehole. Primary solid-removal equipment should include shale shakers, a degasser, a desander, a desilter, and a decanting centrifuge. All of these parts are installed on top of the mud tanks.
Impeller sizes are determined by calculating the TOR (sometimes called the time of rollover) for each compartment. This is the time, in seconds, required to completely move the fluid in a compartment (Table 10.1) and can be calculated by knowing the tank volume and impeller displacement:
TOR = (Vt⁄D)×60
where
. Vt=tank volume, in gallons or liters . D=impeller displacement, in GPM or LPM (as displayed in Table 10.2).
For flat and canted impeller applications, TOR should range between 40 and 85 seconds. As the TOR approaches 40 seconds, the chance for vortex formation and possible air entrainment increases. At values greater than 85 seconds, the proper suspension may be jeopardized and solids will begin to settle.
Table 10.1 Typical Turnover Rate Values, in seconds
Impeller Type
Removal
Addition
Suction
Reserve
Pill
Canted/flat
50-75
50-75
65-85
50-80
40-65
Table 10.2 60-Hz Impeller Displacement D Values
Diameter Flat Canted Contour
In
Mm
Gpm
1pm
Gpm
1pm
GPM
1pm
20
508
1051
3978
909
3441
N/A
N/A
24
610
1941
7374
1645
6226
N/A
N/A
28
711
2839
10746
2468
9341
5861
22185
32
813
4635
17543
3764
14247
N/A
N/A
38
965
7342
27789
6343
24008
10604
40136
40
1016
8411
31836
7284
27570
N/A
N/A
42
1067
N/A
N/A
N/A
N/A
13940
52762
44
1118
11300
42771
9928
37577
N/A
N/A
45
1143
N/A
N/A
N/A
N/A
16812
63633
48
1219
14401
54508
12512
47358
20020
75776
52
1321
18630
70515
16100
60939
24852
94063
54
1372
N/A
N/A
N/A
N/A
27602
104475
56
1422
N/A
N/A
N/A
N/A
30353
114887
60
1524
N/A
N/A
N/A
N/A
36567
138404
64
1626
N/A
N/A
N/A
N/A
43533
164771
For contour impeller applications, values must be significantly faster (i.e., smaller numbers) to achieve the same results, but because of the impeller design, air entrainment is less probable. In symmetrical compartments, the fluid has a nearly equal distance to travel from the center of the impeller shaft or from the impeller blade tip before it contacts the vessel wall. Agitators should be placed where the shaft is centered in the tank or compartment.
When defining the area in which to mix, it is best to work with symmetrical shapes like squares or circles (as viewed in a plan drawing or overhead view of the tank layout). Rectangular tanks should be converted to nearly square compartments if possible. Maximum fluid working volumes in compartments should not be higher than 1 foot (about 3⁄10 m) from the top of the tank. This will allow for a little extra capacity in emergencies, slightly out of level installations, and/or fluid movement on floating rigs.
Working volume for square or rectangular tanks is calculated by knowing dimensional values for length (L), width (W), and height (H; in feet for gallons, in meters for liters):
For gallons:
Vt = L × W(H− 1)× 7.481
The working volume for round tanks with flat bottoms is: For gallons:
Vt = Π r²(H−1)× 7.481
For liters:
Vt = Π r²(H−0.3)× 1000
For round tanks with dish or cone bottoms, calculations for working fluid volume are based on straight wall height (i.e., this height is measured from the tank top to where the tank joins the cone or dish at the bottom). This leaves adequate free space above the maximum fluid operating level. In all cases, if H<5 feet (1.5 m), a radial flow impeller should be specified.
Nine distinct mud systems are defined here. The first seven are water-based, while the eighth is oil-based. The ninth category is a specialized one in which air or gas is the continuous fluid. The 9 categories are:
The study of History is the beginning of wisdom. – Jean Bodin
The actual money saved by using correct drilling fluids processing is difficult to document. Most operators regard the cost of drilling wells as proprietary information.
