In drilling long drift side tracking well window was cut in 95/8 casing. After window cutting 81/2"hole drilled with kcl phpa (inhibitive) mud wt 12 ppg upto top of LIII. Reason for 12 ppg mud use due to shale instability above top of LIII. FROM LIII top to land point formation is lime stone and low pore pressure require gel polymer mud (low mud wt 8.6-8.7 ppg) drilling this two section leads to complication and well problem as 12 ppg mud will induce loss in limestone formation.

As from 95/8" casing window was cut and 7" liner was lowered to top of LIII next liner to lower 5" and thereafter 31/2 drain hole. 6" drain holedrilling was not possible. By adopting expandable liner system problem was solved. One extra set of 51/2 expadable liner was lowered. 51/2 " bicentre bit was lowered and 6" drain hole was done. Drilling procedure as belowLowered 7" linerLowered 61/8 " bit/6"×7" bicentre bit and enlarged to landing point using near bit 7" reamer. Lowered 51/2" expandable casing. Lowered 51/2" bi centre bit for making 6" drain hole.6" drain hole was possible to drill using expandable liner and drilling shale and low pressure loss zone isolating above two zone

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