弯曲井眼中柔性钻柱的屈曲问题

利用能量法，研究了弯曲井眼中柔性钻柱的屈曲问题。在力学模型中，考虑了钻柱自重和井眼曲率的影响，给出了弯曲井眼中钻柱侧向屈曲临界荷载的一般形式。钻柱临界压力不仅与钻柱的长度、截面尺寸等有关，还与井眼的曲率有关，且随着曲率的增大，其临界压力随之增大。当弯曲井眼的曲率增大到一定的数值时，钻柱由稳定问题转变为强度问题，其临界压力应由钻柱的强度条件确定。

BUCKLING OF FLEX-STEM IN CURVED WELL

Energy method is used to analyse flex stem buckling in curved well. In the given mechanical model,it is considered that dead load of stem and well curvature have effects on stability of drilling string. The expressions of critical load for flex stem in curved well are presented. The conditions of string buckling are discussed. Theoretical result shows that critical force is not only associated with the length of string and size of cross section, but also with curvature of well. The critical force is raised with increase of curvature. Stability calculation of string is converted into strength calculation,as curvature increases to some critical value,and critical force can be calculated on the strength condition at the moment. The results may give a reference to engineering calculation.