PDC钻头在砾岩地层中的破岩机理与适应性分析

Analysis on Rock Breaking Mechanism and Adaptability of PDC Bit in Conglomerate Formation

PDC钻头在非均质砾岩地层钻进时,不能仅通过磨损来进行优选,应当明确其破岩机理,从而对其应用效果欠佳的情况给予指导。为此,通过有限元软件建立非均质砾岩模型,对PDC单齿破碎砾石地层进行模拟,明确破岩机理,并提出优选建议。分析结果表明:切削齿在砾岩地层切削时,对小粒径砾岩影响切削力的主控因素为胶结物和基质强度,对大粒径砾岩影响切削力主控因素为砾石本身的固有剪切强度;在砾岩地层中,切削齿齿形推荐选用斧形齿,其半径尽量与砾石尺寸相匹配,且优先选择大厚度齿,选择二级、螺旋布齿可减轻单齿的损伤;可以通过优选新型异质材料来改善切削齿力学性能。研究结论可为提高PDC钻头在砾岩地层中的适应性提供理论支撑。

When the PDC bit is used to drill in heterogeneous conglomerate formation,it cannot be optimized solely through wear and tear,and its rock breaking mechanism should be clarified to provide guidance for situations where its application effect is not satisfactory.A heterogeneous conglomerate model was built using finite element software to simulate the breaking of conglomerate formation by PDC cutter,clarify the rock breaking mechanism,and propose optimization suggestions.The analysis results show that when the cutter is working in conglomerate formation,the main control factors influencing cutting force are the strength of cement and matrix for small size conglomerate,and the inherent shear strength of gravel itself for large size conglomerate.In the conglomerate formation,the axe-shaped cutter is recommended to be used as the cutter shape,its radius should match the size of the gravel as much as possible,large thickness cutter is preferred,secondary and helical cutter arrangement can reduce the damage of single cutter.The mechanical properties of cutter can be improved by optimizing new heterogeneous materials.The research conclusions provide theoretical support for improving the adaptability of PDC bit in conglomerate formations.