在钻井工程中，盐膏层的显著特征是井眼形成后地层易发生塑性变形和井眼缩径，造成卡钻和大量的人力、物力、财力的损失，甚至导致钻井失败。将拉格朗日元法应用于石油钻井所遇的盐膏地层，利用ＦＬＡＣ程序分析了盐膏地层的缩径变形。分析结果表明，在允许缩径率下，钻井液密度有一个临界值，正常钻进的必要条件是钻井液密度应该大于此临界值。 In the drilling engineering, the salient features of the salt-and-paste layer are that plastic deformation and borehole diameter are easy to occur in the formation after the wellbore is formed, causing the stuck pipe and a lot of manpower, material and financial losses, and even drilling failure. Applying the Lagrangian method to the salt paste formation encountered in oil drilling, the shrinkage deformation of salt paste formation was analyzed by FLAC program. The analysis results show that there is a critical value of drilling fluid density under the allowable reduction rate, and the requirement of normal drilling is that the drilling fluid density should be greater than this critical value.