Abstract: A new rock-breaking mechanism of releasing internal energy was developed on the basis of the actual situation in gas drilling and the difference between gas drilling method and normal drilling method.This rock-breaking mechanism for gas drilling relies on the rock broken away from tremendous pressure to release the tremendous internal energy.The rock-breaking process includes the primitive accumulation of rock internal energy,the internal energy expansion,radial expansion of rock and producing cracks,crack expansion and cuttings caused by bit teeth and bit knocking,rock brittle explosion.The rock breaking can be changed from plastic broking in normal drilling to brittle explosion in gas drilling.Application of this new method in Xushen Gas Field verified that the rock-breaking mechanism was accurate.It can be used to the optimization design of bit and parameters in gas drilling.

Key words: gas drilling, rock-breaking mechanism, internal energy releasing, rock breaking, bit optimization, Xushen Gas Field

摘要： 根据气体钻井实钻情况及其与常规钻井方式的差异,借鉴前人研究成果,提出了一种新的破岩机理——内能释放破碎机理,即气体钻井依靠岩石脱离巨大压持作用而将岩石内积聚的巨大内能进行释放的破碎理论。岩石破碎过程为:原始岩石内能积聚;径向岩石受力变化产生的内能膨胀;径向岩石膨胀及微裂纹产生;钻头敲击裂纹扩展及延伸阶段;钻头齿吃入岩石并旋转使裂纹延伸;剪切岩石使其产生脆性炸裂。因此,使岩石破碎由常规钻井的塑性破碎转变为脆性炸裂。在徐深气田进行了现场实钻,初步验证了该机理的准确性。依据该机理可以进行气体钻井的优化设计以及实钻中钻头和钻井参数的优选。

关键词: 气体钻井, 破岩机理, 内能释放, 岩石破碎, 钻头优选, 徐深气田