基于离散元方法的PDC钻头破岩仿真研究

发布时间：2018-05-16 11:15

本文选题：PDC钻头 + 离散元　；参考：《西南石油大学》2017年硕士论文

【摘要】：PDC钻头破岩进尺已占到钻井总进尺的80%以上,它具有单位进尺成本低、钻速高及使用寿命长等特点。目前,PDC钻头在深部地层的钻探开发中得到了广泛的应用,其破岩效率主要受切削齿破岩效率的影响。在钻进过程中,切削齿参数、钻进参数及岩石特性等因素对PDC切削齿的力学性能有着重要的影响。在整个钻进破岩过程中,PDC钻头的切削齿与岩石直接接触,钻头切削参数的不合理将会导致到钻头的稳定性差、切削齿失效等现象的产生,从而降低了使用寿命。因此,研究切削齿与岩石的互作用过程对于减少切削齿损耗和提高破岩效率有着重要意义。本文在前人研究的基础上,通过实验与离散元法研究了 PDC钻头切削齿在动态钻进过程中的力学性能。论文的主要研究内容如下:(1)根据离散元的基本理论和岩石的力学性质,建立了岩石的虚拟单轴压缩实验和虚拟巴西劈裂法实验。在岩石的单轴压缩实验和巴西劈裂法实验的基础上推导出了岩石的细观参数,确定出了岩石的二维和三维离散元模型的本构关系。最后,利用实验对数值模拟结果进行了验证。(2)在岩石的二维和三维离散元模型的基础上分别建立了 PDC单齿切削岩石的二维和三维离散元模型。通过两种模型分别讨论了切削齿前倾角和切削深度对破岩效果的影响规律。(3)建立了 PDC单齿切削圆盘形状岩石的离散元模型,分析了不同切削方式对破岩效果的影响规律,并对切削齿的钻进参数进行了数值模拟分析;建立了 PDC单齿切削凹型和凸型岩石的离散元模型,并讨论了不同岩石地貌形状对PDC单齿破岩效果的影响。(4)建立了 PDC钻头单刀翼破岩离散元模型,分析了机械钻速与转速对各切削齿的影响规律。并针对PDC单齿在切削岩石过程中的"攻击性"与破碎比功进行了研究。在相同机械钻速和转速情况下,切削齿的扭矩和轴向力均随钻头中心轴线距离的增大呈先增大再减小的变化趋势。各切削齿所受的切削力均随机械钻速的增大而增大,且肩部附近齿的切削力最大,而转速对切削力的影响较小。其它条件不变,机械钻速对"攻击性"的影响较小;切削齿的"攻击性"随转速的增大而增大。(5)建立了 PDC全钻头破岩离散元模型,并对全钻头各切削齿的扭矩与轴向力的分布趋势作出了预测,利用PDC全钻头破岩室内台架实验对该模型的计算结果进行了验证。讨论了全钻头各切削齿的载荷与破碎比功对破岩效果的影响;并针对全钻头各刀翼切削齿的扭矩和轴向力进行了对比分析。研究结果表明:在PDC全钻头破岩过程中,钻头包络面及外锥附近切削齿的扭矩值大于其它切削齿,轴向力沿钻头包络线由中心到外侧呈逐渐减小的变化趋势。随钻头径向距离的增大时,各刀翼切削齿的扭矩先增大再减小,而轴向力则逐渐减小。通过全钻头破碎砂岩数值模拟结果的钻压值和扭矩值与实验测试的误差分别为9.32%和3.64%。证实了 PDC全钻头破岩离散元模型的准确性与可行性。
[Abstract]:The rock breaking step of PDC bit has accounted for more than 80% of the total drilling length. It has the characteristics of low cost, high drilling speed and long service life. At present, PDC bit has been widely used in the drilling and development of deep strata, and its rock breaking efficiency is mainly influenced by the cutting efficiency of cutting teeth. In the process of drilling, the parameters of cutting teeth and drilling parameters are used. The factors such as number and rock characteristics have an important influence on the mechanical properties of the PDC cutting teeth. In the whole drilling and breaking process, the cutting teeth of the PDC bit are directly contacted with the rock. The unreasonable cutting parameters of the bit will lead to the bad stability of the bit, the failure of the cutting teeth and so on, thus reducing the service life. Therefore, the study of the cutting teeth will be reduced. The interaction process of cutting teeth and rock is of great significance for reducing the loss of cutting teeth and improving the efficiency of rock breaking. On the basis of previous studies, this paper studies the mechanical properties of PDC bit cutting teeth in dynamic drilling through experiments and discrete element method. The main research contents of this paper are as follows: (1) according to the basic theory of discrete element and the basic theory of discrete element, On the basis of the mechanical properties of rock, the virtual uniaxial compression experiment of rock and the experiment of the virtual Brazil splitting method are established. On the basis of the uniaxial compression experiment of rock and the experiment of the Brazil splitting method, the mesoscopic parameters of rock are derived and the constitutive relation of the two and three dimensional discrete element model of the rock is determined. Finally, the numerical simulation junction is used in the experiment. The results are verified. (2) on the basis of the two-dimensional and three-dimensional discrete element models of rock, the two-dimensional and three-dimensional discrete element models of PDC single tooth cutting rocks are established respectively. Through two models, the influence rules of the cutting tooth dip angle and the cutting depth on the rock breaking effect are discussed respectively. (3) the discretization of the PDC single tooth cutting disc shape rock is established. The influence law of different cutting methods on rock breaking effect is analyzed, and the drilling parameters of the cutting teeth are simulated and analyzed. The discrete element model of the PDC single tooth cutting concave and convex rock is established, and the influence of different rock geomorphic shapes on the PDC single tooth rock breaking effect is discussed. (4) the single wing breaking rock of the PDC bit is established. In the discrete element model, the influence of the mechanical drilling speed and speed on the cutting teeth is analyzed. The "aggressiveness" and the crushing work of the PDC single tooth in the process of cutting rock are studied. The torque and axial force of the cutting teeth increase first and then decrease with the increase of the distance between the center axis of the drill and the same mechanical drilling speed and speed. The cutting force of each cutting tooth is increased with the increase of the mechanical drilling speed, and the cutting force of the teeth near the shoulder is maximum, and the speed has little influence on the cutting force. Other conditions are not constant, the influence of the mechanical drilling speed on the "aggressiveness" is smaller; the cutting tooth "aggressiveness" increases with the speed of the cutting. (5) the PDC whole bit rock breaking rock is established. The discrete element model is used to predict the distribution trend of torque and axial force of the whole bit cutting teeth. The calculation results of the model are verified by the bench test of PDC full bit rock breaking room. The effect of the load and the crushing specific work of the cutting teeth on the whole bit on the rock breaking effect is discussed. The torque and axial force are compared and analyzed. The results show that the torque value of the cutting teeth of the bit envelope and the outer cone is larger than that of other cutting teeth in the PDC whole bit rock breaking process, and the axial force decreases gradually along the center to the outside of the bit envelope. The moment first increases and then decreases, while the axial force decreases gradually. The accuracy and feasibility of the discrete element model of PDC whole bit breaking rock is confirmed by the error of the drilling pressure and the torque value of the numerical simulation results of the full bit broken sandstone and the error of the experimental test by 9.32% and 3.64%. respectively.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE921.1

【相似文献】