气体钻与泥浆钻全井段钻柱动力学对比研究

全井段钻柱在井内运动过程是一个非常复杂的非线性动力学问题,不可能得到比较完美的解析解,如果采用室内试验或者现场试验研究,其成本又会很高且很难实现。因此,在弹塑性力学、岩石力学和钻柱力学的基础上,以四川某井基本钻井参数和钻具组合为依据,采用有限元法建立了塔式钻具钻至1486m井深时的全井段三维钻柱模型和相应的井筒模型,并且建立了钻头与岩石以及钻柱与井筒之间的随时间变化且有摩擦系数的接触关系和相对应的泥浆钻井模型,对比分析了钻柱在动态钻进过程中的井口参数、钻头上压力和转动速度以及全井段钻柱的弯矩扭矩变化等结果,得出气体钻井与泥浆钻井全井段钻柱的运动规律以及钻铤失效机理的差异。为认识气体钻井全井段钻柱的运动规律提供了新的研究方法,对气体钻井中钻柱力学、井斜控制和设备等方面的研究都有较好的现实意义。

COMPARATIVE STUDY ON DYNAMICS BEHAVIORS OF THE FULL DRILLSTRING BETWEEN GAS DRILLING AND MUD DRILLING

The movement of the full drillstring is a very complex nonlinear dynamical process.It is impossible to get very much perfect analytic solution and there is high cost of experiment.Thus,based on elasticsplastic mechanics,rock mechanics and drilling string mechanics and the drilling data of some gas well,this paper successfully establishes the complex nonlinear dynamics finite element 3D realtime drilling model of several kilometerslong irregular borehole,and real conditions are considered,such as mutual action between drill bit and rock,unknown contact between tapered drillstring and hole,effect of complicated 3D well trajectories (azimuth angle,deviation angle) and real drilling parameters (WOB,rotating speed).The timevarying data at each point on the long drillstring can be obtained after simulated,including displacement,axial force,stress,bending moment,torque,vibration,and contact force.These data are processed to obtain the perilous stress zones,the severe abrasion areas,the lowest fatigue life section which possibly lead to failure and difference between gas drilling and mud drilling,which can provide theoretical foundations for the application of drillstring failure and prevention.Furthermore,it is useful of this model to study drilling string mechanics,hole deviation control and equipment in air drilling.