山前构造带推覆体段岩石力学实验及钻头选型

在钻遇山前构造推覆体段以花岗岩为主的岩石时，极易发生钻具断损及钻头磨损加剧的情况。文章在通过岩石力学实验分析山前构造的地层岩性特征的基础上，论述了钻具断损与钻头选型的关系。并进行了两种牙轮钻头钻进的室内实验研究。实验结果表明，不同的钻头选型将直接影响钻柱振动的强弱，采用合适的钻头型号将减轻井下事故的产生。以城二井钻头使用效果为实例，建议钻头选型要尽量降低钻头对钻柱振动影响的要求，对焉耆盆地推覆体花岗岩进行钻头选型，在311 mm井段，根据岩石性质推荐的HJ637和减小钻头振动的要求，推荐使用HJT637G的钻头较合适。

LAB EXPERIMENT ON ROCK MECHANICS FOR THRUST BLOCK FORMATION INTERVAL AT MOUNTAIN FRONT STRUCTURAL BELT AND BIT OPTIMIZATION

When drilling through granite-dominated rocks in thrust block interval of mountain front structure, downhole accidents like dill tool breaking often occur and drill bit wear worsened. On the basis of analysis of the lithologic properties of rocks by rock mechanics experiment, it is discussed that the relationship between drill tool failure and bit types. Indoor experiment is made to study the penetration efficiency of two kinds of cone bits. The results show that different bits will produce different levels of vibration to drill string, so bit optimization can reduce downhole accidents to the minimum. The bit application on Well Cheng-2 is taken as a case study to demonstrate to minimize the vibration to the drill string by optimizing bit selection. For 311mm hole sections in granite rocks in the Yanqi Basin, the bit HJ637 is recommended according to the rock properties and the requirements to reduce the bit vibration, but the bit HJT637G is finally recommended to be preferable.