PDC钻头各向异性及对钻具组合造斜特性的影响研究

Study on Anisotropy of PDC Bit and Its Influence on Deflecting Characteristics of BHA

钻头各向异性会影响钻具组合的造斜特性。为确保钻具组合能发挥最好的井斜控制能力,达到最优的井斜控制效果,本文研究了钻头各向异性指数对钻具组合力学特性的影响规律,提出了临界钻头各向异性指数的概念,并对常规钻头各向异性指数计算新方法进行了改进。研究结果表明:钻头各向异性随着切削齿后倾角、摩擦角、钻头尺寸的增大而增大,随着外锥高度、内锥深度、保径部分摩擦面积的增大而减小,可通过改变钻头的结构参数达到增大(减小)钻头各向异性的目的,为PDC钻头的设计提供了理论基础。为了使增斜、降斜钻具组合获得较大的造斜(增斜、降斜)能力,应尽量选择钻头各向异性指数大的PDC钻头;在使用钟摆钻具纠斜时除了要合理确定稳定器的安放位置和钻井参数外,还应该选择钻头各向异性指数较大的钻头。

Anisotropy of the bit will affect the deflecting characteristics of the BHA.In order to ensure that the BHA can exert the best deviation control ability and achieve the best deviation control effect,this paper studies the influence of bit anisotropy index on the mechanical properties of the BHA,puts forward the concept of critical bit anisotropy index and improves the new calculation method of conventional bit anisotropy index.The results show that the bit anisotropy increases with the increase of the back rake of cutter,friction angle and bit size;It decreases with the increase of the height of the outer cone,the depth of the inner cone and the friction area of the diameter maintaining part.The change of structural parameters of the bit may achieve the goal of the bit anisotropy increase(decrease),which provides theoretical basis for the design of the PDC bit.PDC bit with high bit anisotropy index should be selected as far as possible in order to ob-tain greater deflection-building(hole deviation increase and hole deviation reduction)capability of the BHA for hole deviation increase and hole deviation reduction.In addition to reasonably determining the placement position and drilling parameters of the stabilizer,the bit with larger anisotropy index should also be selected when using the pendulum assembly for correcting the deviation.