Research on dynamics model of full hole drilling-string system with three-dimensional trajectory

According to Hamilton Principle and finite element method,the dynamics model for full hole drilling-string system with three-dimensional trajectory was established by synthetically considering some factors.The factors were longitudinal vibration,trans- verse vibration and torsion vibration of drilling string,collision between drilling string and wall of well,friction between wall of well and drilling string,sticky damping between slurry and drilling string,bending effect of moved drilling string caused by slurry in drilling string,differential pressure effect of stratum,attached effect of resistance caused by buckling and interaction between drilling bit and rock.The resolution method for a large nonlinear system with uncertainty,dynamic and quasi-stochastic boundaries was in vestigated.Emulation software for emulating the dynamics characteristic parameters,including displacement,velocity,acceleration and load of drilling string element,was developed.It can be run under freewill drilling parameters,drilling tool,drilling fluid and stratum.