The importance of shale shakers as the primary solids control equipment capable of handling the full returns from the wellbore cannot be over stressed. They must be operated as efficiently as possible, at all times, in order to maximise the amount of solids removed at the first pass.
Solids passing through the shakers will be re-circulated, during which they will be reduced in size. Wear and tear on pumps and tubulars will be the result and the reground cuttings will be even more difficult to remove on their next pass. If the solids are reactive they will require costly chemical treatment and/or whole mud dilution.
Operational Guidelines
- Shakers shall be switched on immediately before running in the hole to cope with mud displaced by the drill string and BHA.
- Coarse mesh top screens shall be used on double deck shakers, to remove the bulk of the large cuttings and thus enable finer screens on the lower deck to function more efficiently.
- Initially, shakers should be fitted with relatively coarse screens, such as 80 mesh, for running in the hole and breaking circulation.
- With new water based polymer mud, or with cold oil based mud after trips, screen blinding may occur during the initial period of circulation. After 1 or 2 circulations, the screens may be changed to finer mesh as the polymer shears, or the mud heats up.
- Flow shall be distributed evenly over all available shakers.
- The finest mesh screens shall be selected, taking into consideration maximum solids separation whilst ensuring that whole mud is not lost and screens are not overloaded.
- Screens should be changed to a finer mesh and square mesh screens should be changed out to equivalent rectangular mesh screens in attempts to alleviate problems of sand blinding.
- A reduction in circulation rate and/or changing to coarser screens should alleviate screen blinding problems resulting from high viscosity mud. However, circulation rate must only be reduced if it is absolutely certain that effective hole cleaning can be maintained.
- Screens shall be inspected regularly and changed out immediately when found as defective. Operations must not be allowed to continue with a torn or ineffective screen.
- Shaker screens shall be washed down regularly with water eg., on connections, for ease of inspection, to maintain screening efficiency and to prolong screen life.
- Shaker screens shall be washed down prior to tripping out of the hole and before shakers are switched off. Cuttings must never be allowed to dry hard upon the screens.
- During milling operations a ditch magnet is placed in the flow ditch.
- Shakers shall be switched off immediately prior to tripping out of the hole. Care must be taken to ensure that the shakers are started before breaking circulation for any reason, e.g. backreaming and pumping out.
- The shakers shall never be run dry as this will lead to increased wear and premature screen failure.
- The shakers shall never be by-passed, except if absolutely necessary, in the case of running LCM in the mud.
- Adequate stocks of screens, in a variety of useful sizes, shall be maintained on location at all times.
Screen Selection
The performance characteristics of commonly used screens are shown in the following table:
|
SCREEN TYPE / MESH |
OPENING SIZE (MICRONS) |
OPENING SIZE (INCHES) |
OPENING AREA (%) |
BRANDT |
DERRICK |
||
|
SQUARE |
|
|
|
|
|
||
|
8×8 |
2464 |
0.0970 |
60.2 |
S8 |
|
||
|
10×10 |
1950 |
0.0750 |
56.3 |
S10 |
|
||
|
12×12 |
1524 |
0.0600 |
51.8 |
S12 |
|
||
|
14×14 |
1295 |
0.0510 |
51.0 |
S14 |
|
||
|
16×16 |
1130 |
0.445 |
50.7 |
S16 |
|
||
|
18×18 |
955 |
0.0376 |
45.8 |
S18 |
|
||
|
20×20 |
838 |
0.0330 |
43.6 |
S20 |
– |
||
|
30×30 |
541 |
0.0213 |
40.8 |
S30 |
DX24 |
||
|
40×40 |
381 |
0.0150 |
36.0 |
S40 |
DX38 |
||
|
50×50 |
279 |
0.0110 |
30.3 |
S50 |
DX50 |
||
|
60×60 |
234 |
0.0092 |
30.5 |
S60 |
DX70 |
||
|
80×80 |
178 |
0.0070 |
31.4 |
S80 |
DX84 |
||
|
100×100 |
140 |
0.0055 |
30.3 |
S100 |
DX110 |
||
|
120×120 |
117 |
0.0046 |
30.9 |
S120 |
DX140 |
||
|
150×150 |
105 |
0.0041 |
37.4 |
|
|
||
|
200×200 |
74 |
0.0029 |
33.6 |
|
|
||
|
250×250 |
63 |
0.0025 |
36.0 |
|
|
||
|
325×325 |
44 |
0.0017 |
30.0 |
|
|
||
|
8×20 |
2362×762 |
0.0929×0.0300 |
45.7 |
B20 |
R25 |
||
|
20×30 |
898×465 |
0.0350×0.0183 |
39.1 |
B40 |
R30 |
||
|
20×40 |
910×310 |
0.0358×0.0122 |
36.8 |
B60 |
R40 |
||
|
20×60 |
940×195 |
0.0370×0.0077 |
34.0 |
B80 |
|
||
|
40×50 |
419×292 |
0.0165x.0115 |
38.3 |
|
|
||
|
24×60 |
830×200 |
0.0327×0.0079 |
41.5 |
|
|
||
|
30×70 |
660×178 |
0.0260×0.0070 |
40.3 |
|
|
||
|
40×60 |
406×195 |
0.0160×0.0077 |
29.4 |
B100 |
R600 |
||
|
40×80 |
460×140 |
0.0181×0.0055 |
35.6 |
B120 |
R80 |
||
The following screen selection are for guidance only. Final screen sizes to be selected based on flow rate, number of shakers and drilling conditions.
|
Hole Size |
Suggested Screen Size (Mesh) |
|
17 ½ |
80-100 |
|
12 ¼ |
120-150 |
|
8 ½ |
150-200 |