Drilling Fluid Technology for Well Kenkyak-8102.

An amphoteric polymer sulfonate drilling fluid was designed for use in Kenkyak to drill the sub-salt reservoirs characteristic of high pressure and high temperature.Field application showed that this high density mud had good rheology,and slat formation drilling was done successfully.Down hole troubles previously encountered were greatly minimized.Average percent borehole overcut was only 5.62%.Highest drag encountered during POOH was less than 10 tons.In drilling Well Kenkyak-8102,drilling fluid rheology was greatly optimized and was lower than that of the mud used in the adjacent well 235.Marsh funnel viscosity of a mud with a density of 1.95 g/cm3 can be kept between 70 and 90 sec.