具有独立缓冲结构的PDC—牙轮复合钻头研制

A PDC-roller hybrid bit with an independent buffer structure

油气勘探开发过程中,难钻地层钻井效率低、钻头寿命短是影响深井、超深井钻井周期和成本的瓶颈问题。钻头工作过程中切削结构轮流与井壁接触而产生的多边形效应是导致钻头不稳定工作、切削齿冲击失效的主要因素。为提高钻头工作稳定性,提出了具有独立缓冲结构的PDC—牙轮复合钻头新结构,并针对四川盆地茅口组Ø311.2 mm井段常规PDC钻头冲击失效严重的问题,设计了3+3+3型(3个主刀翼、3个牙轮以及3个独立缓冲刀翼)的独立缓冲结构复合钻头,开展了全尺寸钻头室内钻进对比实验,并在川渝页岩气区块茅口组—栖霞组地层进行了实钻应用。研究结果表明:①独立缓冲结构复合钻头在常规复合钻头的牙轮切削结构和固定切削结构之间的空隙部位增设独立缓冲刀翼,有效缓解了多边形效应,对PDC齿形成很好的缓冲保护,同时分担了过大的钻压,限制了切削齿吃入深度,进而防止了钻头产生粘滑振动;②独立缓冲结构复合钻头钻压和扭矩波动小,扭矩为PDC钻头的1/5;③独立缓冲结构复合钻头取得了单只钻头进尺170 m的记录,比邻井同层位单只PDC钻头最高进尺提高了73.5%。结论认为,独立缓冲刀翼对提高钻头的稳定性起到了关键作用,不仅提高了钻头寿命,而且有效提高了复杂难钻地层及复杂结构井的综合钻井时效,有效降低了油气勘探开发成本。

In the process of oil and gas exploration and development,low drilling efficiency and short bit lifespan in hard-to-be-drilled strata are the bottleneck problems impacting the drilling cycles and costs of deep and ultra-deep wells.The polygonal effect generated by the alternating contact between the cutting structure and the wellbore in the operation process of the drill bit is the main factor leading to the unstable operation of the drill bit and the impact failure of the cutting teeth.To improve the operation stability of drill bit,this paper proposes a new type of PDC-roller hybrid bit with an independent buffer structure.In response to the serious impact failure of conventional PDC drill bits in theØ311.2 mm well section of Maokou Formation in the Sichuan Basin,a 3+3+3 type(3 main blades,3 roller-cones,and 3 independent buffer blades)hybrid bit with an independent buffer structure is designed.Then,laboratory full-scale bit drilling comparison experiments are conducted.In addition,it is applied to the actual drilling in the Maokou Formation-Qixia Formation of Sichuan-Chongqing shale gas block.And the following research results are obtained.First,superior to conventional hybrid bits,the one with an independent buffer structure has an additional independent buffer blade in the clearance between the roller cutting structure and the fixed cutting structure,which effectively alleviate the polygon effect to provide the buffering protection for PDC cutters while sharing the excessive weight on bit(WOB)to restrict the cutting depth of cutting teeth,so as to prevent the stick-slip vibration of drill bit.Second,the WOB and torque of the hybrid bit fluctuate in a small range,and its torque is 1/5 of that of the PDC bit.Third,the hybrid bit has set up a new record of drilling footage of 170 m with one single drill bit,which is 73.5%greater than the maximum drilling footage of one single PDC bit in the same layer of the adjacent well.In conclusion,the independent buffer blade plays a key role in improving the stability of the drill bit,which not only prolongs its service life,but effectively improves the composite drilling efficiency in complex and difficult-to-be-drilled strata and complex-structure wells and reduces oil and gas exploration and development costs.