When coiled-tubing operations include horizontal work, the fluid should have elevated LSRV as measured on a Brookfield viscometer at a shear rate of 0.0636 sec– 1. Rheologically engineered fluids, such as F LO -P RO , with elevated LSRVs have been used to drill horizontally with both conventional and coiled-tubing drilling rigs since 1991 with dependable success. F LO -P RO T prevents cuttings beds in the horizontal portion of the hole without excessive reliance on drilling practices such as backreaming and circulation.