气体钻井钟摆钻具组合的有限元分析法

在现行的钟摆钻具设计过程中,将第一个稳定器及其以下钻铤简化为简支梁进行计算。常规钻井液钻井时,钻压常远远大于稳定器以下钻铤浮重,忽略钻柱自身重力对轴向力的影响;而气体钻井时,钻压小,钻铤浮重大,此时钻铤自身重力的影响不得不考虑。以管单元模拟钻具的物理及几何特性,以间隙单元模拟钻具与井壁接触,采用有限元法,对气体钻井过程中下部钻具组合受力及变形进行了动态数值模拟,对单稳定器及双稳定器钟摆钻具组合进行了分析。该有限元模型不仅考虑了钻铤自身重力的影响,而且考虑了钻铤自转对其变形的影响,为钻柱力学分析提供了一种有效的手段,也为气体钻井防斜打直提供了理论依据。

Finite Element Analysis on Pendulum Bottom Hole Assembly on Gas Wells

During the design of the pendulum assembly,the first stabilizer and following collars are usually simplified as a free beam.In conventional drilling,the weight on bit(WOB) is bigger than the buoyant weight of collars,the impact of collar weight on axial force is usually ignored.While in air drilling,the WOB is lower and the buoyant weight of collars is bigger,so the impact of collar weight on axial force has to be considered.In this paper,physical and geometrical characters of drilling tools were simulated using pipe element,and the contact between drilling tools and wellbore was simulated using gap element.Using finite element method(FEM),the stress and the deformation of bottom-hole assembly(BHA) was numerically simulated to analyze the structure of the single-stabilizer and double-stabilizer pendulum assembly.In this model,the collar weight and the impact of the drilling collar rotation on its deformation were considered.This paper offered an effective method for the mechanics analysis of drilling string and the theoretical foundation for preventing well deviation in air drilling.