The well need to be sidetracked from 945/8″ csg. window using a 8 1/2″ bit. Two problematic sections have to be penetrated. Parigi (dolomite & sand) and Pre-Parigi (limestone) are two thick formations for sloughing shale, losses, tight hole, bit balling and stuck pipe across limestone stringers associated with these two formations. At the nearest (previous) well had to pump more than 20 cement plugs to combat loss of circulation in these notorious sections.
The 8½” hole was drilled from 9⅝” casing window at 2,583 ft. FRACSEAL was maintained at 648 ppb in the 9.1 ppg Low pH Desco active mud. Drilling at 2960 ft had initial loss at 10-20 bph. FRACSEAL concentration was increased to 7.5 ppb and seepage losses reduced and hole was static and stable until drilling at 3,400 ft. Sometimes sudden high losses were detected, then displaced hole with FRACSEAL pill containing 30 ppb FRACSEAL and 10 ppb CaCO3 Medium while keeping 6H8 ppb in the active mud.
None cement plugs needed for stopping losses in this well. Had a relative smooth drilling of the long section of 8½” hole up to to 7″ liner point at 8,450 Y (MD). The 7″ liner was run and set without any problem.