Cuttings Bed Suppression
Cuttings beds formation in deviated holes can be suppressed by using muds with exceptionally good suspension characteristics. However, high flow rates are still necessary since the beds can never be totally eliminated. For water based mud, the best conventional additive for this purpose is XC polymer. All the major service companies now offer low shear enhancers (sometimes referred to as rheology modifiers) for oil based muds.
A simple force balance approach can be used to determine the minimum mud rheology necessary to maintain drilled cuttings in suspension:
Where:
06 = Fann 6 rpm reading
03 = Fann 3 rpm reading
Dp = Cuttings diameter (in)
For example, a 1.4 sg (11.7 ppg) mud, with Fann 6/3 readings of 21/20 lb/100 ft2, will support a 6mm (1/4 in) cuttings with an sg of 2.1.
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