油气井井漏井壁与波纹管接触应力分析

基于钻井过程中的波纹管堵漏技术，采用有限元分析方法对与井壁接触情况下的堵漏波纹管膨胀过程进行了研究。模拟了井眼中波纹管的膨胀变形，得到了波纹管施工加压膨胀和井壁接触过程中的等效应力分布云图、波纹管的位移、应力变化规律，以及波纹管膨胀后和井壁的接触状况。波纹管加压膨胀变形过程中，其应力、应变对应于管体几何形状呈对称分布，管体各处的等效应力和应变不同。波纹管并非在全周长上与井壁发生接触，部分弧段没有接触压力。膨胀内压增加时，接触区域扩大，接触压力有明显升高。井壁只在波纹管与其最先接触点，以及随后接触的波峰顶点处会出现较高的Mises应力。该方法为油气井钻井过程中出现的井漏波纹管堵漏施工时膨胀内压的确定提供了依据。

Analysis of contact stress between thief zone wellbore and bellow pipe

Bellow pipe is often used for plugging during drilling. The expanding process of the bellow pipe in contact with the borehole wall was analyzed. The equivalent stress nephograms, the variation rule of pipe displacement and stress on the bellow pipe under expansion were obtained. It was found that the stress and strain of the pipe were symmetrically distributed over the geometric shape of the pipe，the equivalent stresses and equivalent strains at different points of the pipe varied with the curvature radius. The equivalent stress and strain varied at different areas. The bellow pipe does not contact the borehole along the whole circumference. There is no contact stress at some parts of the circumference curve. The contract curve and pressure increased with the internal expanding pressure. The rather high Mises stress only appeared at the most initial contact point and the wave crest coming next. This method will provide a reference for determination of expanding pressure for plugging with bellow pipe.