钻头冠部形状对破岩效果的影响

发布时间：2018-12-27 18:28

【摘要】：用有限元方法模拟了不同形状钻头的破岩效果,研究了地层应力分布及裂缝延伸模式。按照国际钻井商协会(IADC)分类标准设计了14种钻头形状。设计了地层模型,给出了钻头尺寸、地层性质、网格划分方法和边界条件等。采用拟静态条件和质量缩放法以减少模拟时间、提高模拟精度。模拟结果表明,对于9种常用钻头形状,增加锥体高度高应力区面积会增大,而保径高度与产生的应力之间没有明显关系。减小保径高度,高应力区从鼻端和中心部位转移到保径区。对于非常用钻头形状,凸形钻头产生的应力场较大,双心钻头导眼体底部应力较集中。裂缝主要产生在保径区和鼻端,锥体高度和保径高度较大的钻头产生的垂直裂缝较长。使用平形和凸形钻头时没有产生较长的垂直裂缝。双心钻头可抑制保径区的垂直裂缝,却使地层更易出现水平裂缝,有中间段扩眼器的钻头造成的井壁损伤更小。
[Abstract]:The rock breaking effect of bits with different shapes is simulated by finite element method. The distribution of formation stress and fracture extension model are studied. According to the (IADC) classification standard of the International Association of drilling operators, 14 drill bit shapes were designed. The formation model is designed, and the bit size, stratigraphic properties, meshing method and boundary conditions are given. Quasi static condition and mass scaling method are used to reduce simulation time and improve simulation accuracy. The simulation results show that the area of high stress zone increases with the increase of cone height for nine common bit shapes, but there is no obvious relationship between the diameter preserving height and the stress generated. Reducing the diameter preserving height, the high stress region is transferred from the nasal end and the center to the diameter preserving area. For the non-common bit shape, the stress field of convex bit is larger, and the stress at the bottom of the guide hole of double core bit is more concentrated. The fractures mainly occur in the diameter preserving area and the nose end, and the vertical fractures of the drill bit with higher cone height and diameter preserving height are longer. Flat and convex bits are used without longer vertical cracks. The double core bit can restrain the vertical fracture in the diameter keeping area, but it makes the horizontal fracture appear more easily in the formation, and the hole wall damage caused by the hole reamer in the middle section is smaller.
【作者单位】： School
【分类号】：TE921.1

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