Optimal and fast drilling technology for directional wells in deep undercompacted formation in Bayan Oilfield
The formation in Bayan Oilfield has such characteristics as rapid subsidence,undercompaction,and complex lithology.The reservoir depth is over 4 000 m,and the well depth averages over 5 000 m.In drilling operation,the challenges such as instability of borehole wall,slow ROP in directional wells,and difficulties in trajectory control are prone to exist,and the well construction cycle is as long as 54.96 days.To solve such problems,the research on optimization of well trajectory,individualized optimization design of drill bit,application of accelerating tools by reducing friction and drag,as well as optimization of drilling parameters and drilling fluid performance has been carried out.The results prove that:The drop-off rate of 1.2(°)/30 m is conducive to drilling operation.The five-blade PDC bit with shallow inner cone,irregular teeth,and damping teeth in the rear row can boost the impact resistance and improve ROP."Hydraulic oscillator+drill string torsion control system"and"rotary steering+low speed high torque screw"can increase the ROP in directional section by more than 50%.The engineering parameters of"low bit pressure,high speed and large displacement"can speed up the upper formation by more than 9%,while that of"high bit pressure,high speed and low displacement"can speed up the deep formations by more than 14%.The combination of polymer drilling fluid system and micro nano plugging agent maintain the wellbore stability.The field application of 90 wells in 11 platforms shows that,the average ROP is increased by 8.89%,and the well construction cycle is shortened by 23.94%.Optimal and fast drilling technology has greatly accelerated the drilling speed and reduced the cost in Block Xinghua 1 in Bayan Oilfield,which provides a reference for rapid well construction and production capacity construction in similar reservoirs.
deep layerundercompactioncluster welloptimal and fast drillingmicro-nano pluggingROPBayan Oilfield
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