WorldOil

Flat-rheology mud for deepwater wells

Flat-rheology drilling fluid, in routine use in the Gulf of Mexico since 2004, was designed to prevent loss of circulation to induced fractures resulting from the elevated equivalent circulating density (ECD) that is typical in cold deepwater drilling. The drilling fluid functions differently from lost-circulation material (LCM). The term flat rheology, considered misleading by some engineers, can describe two distinct rheological concepts. An early definition of flat rheology (FR) describes a rheological measurement at a 6-rpm test speed as being as close as possible to the 100-rpm reading or the yield point measured using an industry-standard couette viscometer, measured at a single temperature of 50°C.