Aiming at the problem that the physical properties of the supercritical carbon dioxide drilling process change with the change of the temperature and pressure of the wellbore, the effect of the change of the supercritical carbon dioxide on the directional buckling of the directional well string under cyclic conditions is studied.The critical buckling pressure of the directional well string in the supercritical carbon dioxide was calculated by establishing the buckling formula of the temperature, pressure, viscosity, density and other physical parameters related to the supercritical carbon dioxide.Conventional drilling fluid conditions and no drilling fluid conditions under the conditions of the column are compared.The results show that the buckling critical load of the initial concave curved string in the directional well is smaller than that in the straight well, that is, it is not easy to bend.The effect of supercritical carbon dioxide on the critical buckling pressure of the column is different under different initial mass flow rate, so the change of inlet mass flow has little effect on the critical buckling load.The critical buckling pressure of the supercritical carbon dioxide is not significantly different from that of the non-drilling fluid and the conventional drilling fluid, and the critical buckling pressure of the supercritical carbon dioxide is less than that under the condition without drilling fluid Pressure, which is greater than the critical buckling pressure under conventional drilling fluids.%针对超临界二氧化碳钻井过程中其物性随井筒温压的变化而变化显著的问题,研究了在循环条件下超临界二氧化碳物性的变化对定向井管柱的屈曲影响,通过建立与超临界二氧化碳相关的温度、压力、黏度、密度等物性参数模型,结合定向井管柱的屈曲计算公式,计算出定向井管柱在超临界二氧化碳中的临界屈曲压力,并与在常规钻井液条件下和无钻井液条件下的管柱受力情况进行对比.计算结果表明:在定向井造斜段初始下凹弯曲管柱的屈曲临界载荷比直井中的大,即不易弯曲.超临界二氧化碳在不同初始质量流量下对管柱的临界屈曲压力影响较小,故入口质量流量的改变对管柱临界屈曲载荷的受力影响较小.超临界二氧化碳与无钻井液及常规钻井液相比,在上部钻杆段临界屈曲压力差别不大,在下部钻铤处区分明显,超临界二氧化碳的临界屈曲压力小于无钻井液条件下的临界屈曲压力,大于常规钻井液下的临界屈曲压力.
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