【摘要】 针对钻井过程中在岩盐层和塑性泥岩层经常发生井眼缩径现象,由现场的观测和变形量级的分析可知,井眼的缩径需要用有限变形理论进行研究.本文应用有限变形次弹-塑性理论,建立了井眼的缩径模型.采用对数应变和Mohr-Coulomb准则,给出变形的协调方程和岩石材料的全量本构方程;在推导出求解问题控制方程的基础上,数值计算给出井眼附近的应力和应变场;在讨论井眼收缩率与本构参数中指出,本构参数n和C0是影响收缩率的重要因素.计算结果与现场观测结果相吻合.这些结果为岩石材料本构参数的实验测定和调节钻井液密度防止井眼失稳提供理论参考依据.更多还原

【Abstract】 Shrinkage of the wellbore always appears on the halite and plastic mudrock strata in the process of drilling.According to field observation and the deformation magnitude,shrinking of the wellbore belongs to the category of finite deformation,so the model of wellbore shrinking was established here by using the hypoelasto-plastic finite deformation theory.The deformation compatibility equations of rock materials are given by choosing logarithmic strain and Mohr-Coulomb criterion;based on the derived control equation for solving problem,the stress and strain field around the wellbore is obtained by numerical calculation.In the discussion on the shrinking rate of the wellbore and its constitutive parameters,the results indicate that constitutive parameters n and C0 are key factors affecting the shrinkage ratio,and the calculation results are coincident with field observations.All of these conclusions can provide theoretical reference for the experimental determination of constitutive parameters of rock material and adjustment of drilling fluid densities to prevent wellbore instability.更多还原