Drilling ~2000m of 26" hole - best practices

25 June 2012 Dear Members

Our engineering group is planning HTHP well that will be drilled offshore NWS, Australia from JU rig. One of the challenges that will be met on this well is long, vertical 26" hole section. 1830m of 26" hole section will be drilled in order to achieve good 20" shoe LOT to drill next hole section. We are considering different options how to approach this challenge: Casing drilling, 11 3/4" motors with 26" PDC's and 11 3/4" DC, 17 1/2" x 26" HO BHA's. Formations are predominantly limestone/sandstone. 17 1/2" hole sections on offset wells were drilled to that depth and were successfully cased. Biggest issue in such a long 26" hole section will be hole cleaning. Diverter will be rigged up and close circulating system will be used.

I am looking for information on experience in drilling long 26" hole sections from jack up rigs, risks , lessons learned

Please let me know if anything above needs to be clarified

Appreciate your time and help

Aydin

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