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应用有限元法,考虑地层的层理性,假设地层为横观各向同性的,根据弹性理论,对下部钻具组合及地层进行三维分析。把钻柱及相关地层作为整体考虑,钻柱部分采用三维梁单元,地层部分采用六面体等参单元附以四面体单元填充,通过适当的简化和处理,解决了微机内存不够的困难。编制了相应的计算程序,应用该程序,可以得到不同的地层倾角和地层倾向变化时钻头侧向力(并斜力和方位力)的变化情况。给出地层对钻头侧向力影响的定量解答。
Using the finite element method, taking into account the layer rationality of the strata, assuming that the strata are transversely isotropic, a three-dimensional analysis of the lower hole assembly and strata is performed based on the elastic theory. Considering the drill string and related strata as a whole, the three-dimensional beam element is used for the drillstring part, and the tetrahedron is used for the stratification part. The proper simplification and handling of the drillstring part solves the problem of insufficient memory in the microcomputer. Corresponding calculation programs are compiled, and the application of this program can get the change of bit lateral force (as well as the oblique force and azimuth force) when different formation dip and formation inclination change. The quantitative solution to the effect of formation on lateral force of bit is given.