分散扶正与保径的新型PDC钻头设计与现场试验

Design and field test of the new PDC bit with divided gage pad

PDC钻头因具有较高的破岩效率而被广泛应用,但在硬地层以及软硬交错、含砾等复杂地层中,由于受力变化频繁和工作稳定性降低,PDC齿易发生冲击崩损而导致钻头使用寿命显著降低。针对PDC钻头在上述复杂地层中寿命短的问题,提出分散扶正与保径的PDC钻头新方案,并对PDC钻头进行工作稳定性分析、主切削结构设计与优化、分散扶正与保径结构设计以及钻头流场分析等。针对大段砂砾岩层的恶劣条件,开发研制的以分散保径结构为主要特征的新型PDC钻头在现场试验中取得了成功,单只钻头总进尺达1 339.16m,其中包括605 m砂砾岩层,节约6次起下钻,钻头钻速高、寿命长,且井眼质量好。研究结果表明:分散扶正与保径技术能显著提升钻头的工作稳定性,使PDC钻头对硬地层、不均质地层的适应性得到明显改善,是提高复杂难钻地层PDC钻头工作性能的有效技术手段。

PDC bit is widely used because of its high drilling efficiency.Nevertheless,when drilling in complex formations,such as the hard laminated formation,gravel formation and multi-interbedded formation,due to frequent stress changes and lower working stability,the service life of the PDC bit will be significantly reduced since impact failure will occur within the PDC cutters that suffer severe load fluctuation.Aiming at prolonging service life of the PDC bit used in complex formations,a new PDC bit with divided gage pad was put forward,and the analysis on the working stability and flow field characteristic for PDC bit were conducted.Based on the analysis results,the main cutting structure and the divided gage pad was designed and optimized.Regarding to the situation of large dimensions of sandstone and conglomerate,the new PDC bit with divided gage pad was proved to be successful in field test.Results of the field test showed that the borehole was of high quality,and the total footage of the PDC bit was 1 339.16 m,including 605 m sandy conglomerate formation,saving 6 tripping times with high rotation speed and long service life.The research result shows that the technique of divided gage pad can significantly improvethe working stability and adaptability of the PDC bit in hard or inhomogeneous formation,and this proves that the technique is effective to improve the performance of PDC bit drilling in complex formations.