高温高压下钻头破岩及磨损规律研究

Study on Drill Bit Rock Cutting and Wearing Pattern under High Temperature and Pressure

在高温及高压下,岩层的塑性和硬度增大,破碎方式也有相应的变化。之前在常温常压下容易破裂的岩层,在深井条件下则塑性较大,不容易破碎。因此,利用“20MN伺服控制高温高压岩体三轴实验机”及钻进控制系统,在不同的大尺寸岩石上采取不一样的钻压和转速来完成正交试验,进而测试了不同破岩参数下的钻进速度和扭矩,详细地探究了200℃高温及三轴应力情况下岩石的切削规律以及岩石的磨损规律,得到了100MPa(等于井下4000m)时岩石在每一个温度下的切削破碎规律。研究结果表明:在同一温度与转速情况下,切削速度随着钻压的增加而显著加快,在同一温度与钻压情况下,切削速度随着转速加快而大幅度加快;单位破岩能耗随着转速的变慢而降低,随着钻压的变小而增大,与常规下的切削破碎规律具有相似性;在相同转速状况下,随着围压的加大,破碎砂岩所需的负荷也相应提高;基于对钻头破岩过程中破岩规律和磨损规律的分析,得到200℃高温及高压条件对钻头的破岩规律及磨损规律展的影响。

Plasticity and hardness of strata will be increased under high temperature and high pressure,while breakage pattern changed accordingly.Formerly breakable strata under normal atmospheric temperature and ordinary pressure,plasticity will be increased under deep well conditions and not easy to break.Thus using“20 Mn servo-controlled tri-axial test machinefor rock massunder high temperature and high pressure”and drilling control system,applying different bit pressures and rotation rates on different large sized rock mass to complete orthogonal experiment;proceed to test drilling speed and torque under different rock cutting parameters.Then probe into rock cutting and wearing patterns under 200℃high temperature and tri-axial stress in detail,and worked out rock cutting and breakage patterns under 100MPa(amount to underground 4000m)with different temperatures.The study has shown that under same temperature and rotation rate,cutting speed will increase obviously with bit pressure increasing;under same temperature and bit pressure,cutting speed will increase significantly with rotation rate increasing;specific energy consumption will reduce with rotation rate lowering down,increase with bit pressure lowering down,thus similar to conventional cutting breakage pattern;under same rotation rate,with confining pressure increasing,required loads to break sandstone increasing correspondingly;based on rock cutting and wearing pattern analysisin drill bit rock cutting process has worked out impact on drill bit rock cutting and wearing pattern under 200℃high temperature and high pressure.