Hole cleaning during deviated drilling : The effects of pump rate and rheology

In the present paper it is shown that the frictional pressure loss in the annulus is the major contributing part to hole cleaning in deviated wells. A sufficiently large annular frictional pressure loss is required to obtain proper hole cleaning regardless of the drilling fluid design. It is shown that cuttings bed consolidation is the next item to be addressed. A very high frictional pressure loss may be necessary to remove cuttings from the bed if the bed is well consolidated. It is also illustrated how important it is to design a drilling fluid regarding hole cleaning performance at the correct annular frictional pressure loss.