Hard and interbedded formations with conglomerates proved a significant challenge to operator,contrac-tor and Service Company in terms of drilling performance,equipment and tool failure.Fixed cutter bits (polycrystalline diamond compact-PDC)experience severe damage resulting in short distance drilled and trips.Roller cone bit normally drill much slower than a PDC bit.The use of conventional PDC and roller cone bits leads multiple runs and trips,resulting in significant higher cost and rig time.By using the hybrid drill bit which combines fixed-cutter and roller-cone elements,higher penetration rate(ROP)is sustained, drilling distance is increased and vibrations are reduced compared to using only PDC or roller cone bits. Drilling in Tarim Basin,Northwest China has a similar challenge which is to drill the entire conglomeratic interval with improved ROP and reduced vibration while reducing tools/bit related trips. This paper describes the detail of the first fixed-cutter and roller-cone hybrid bit trial in the Tarim Basin,Northwest China.Result shows over 150%ROP improvement over the best offset record.Five PDC bits and one roller cone bit were replaced saving 16 rig days.The bit drilled smoothly without severe vibration(torque related)and equipment/tools failure.
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