基于单齿侵入理论的牙轮钻头钻速方程

考虑井底水平地应力、钻井流体压力及地层孔隙压力,基于单齿侵入理论推导单齿侵入井底岩石的侵深公式,建立纯滚动锥形齿、楔形齿和滚动、剪切复合运动锥形齿等牙轮钻头的钻速方程.通过实验分析刃尖角、井底液柱压力对单齿侵入深度的影响,以及转速、轴向载荷对微钻头、牙轮钻头机械钻速的影响.结果表明:随着牙齿刃尖角的增大,锥形齿和楔形齿的侵深呈指数递减趋势;随着井底液柱压力的增大,牙齿侵入深度呈指数递减趋势,其中锥形齿降低速率大.在软到中硬地层中,牙齿侵入深度大,冲击侵入、回转剪切复合破岩方式的破岩效率高;在硬度地层中,牙齿侵入深度小,纯滚动冲击侵入破岩效率高.为分析实钻时牙轮钻头的机械钻速提供计算方法.

Drilling rate equation of cone bit basied on single tooth intrusive theory

Considering the condition of the bottom hole pressure,based on single tooth intrusive theory to give invasion depth formula,we build drilling model of true rolling conical insert,true rolling chisel teeth and conical insert of compound motion of roll and shear.We have nalyzed the impact of bit angle and fluid column pressure on invasion depth and rotation speed and drill pressure on penetration rate of micro drill bit and cone bit.The results show that the invasion depth of conical insert and chisel teeth decrease exponentially with bit angle and fluid column pressure increasing,whose conical insert is more obvious.In the soft to medium-hard formation,the larger the invasion depth is,the more effective rock breaking is,which combines impact and shear.In the hard formation,the smaller invasion depth is,the more effective rock breaking of true rolling impact is.