The Research On Dynamic Analysis Of Drillstring Solving Method

In the drilling state, the drill string is collision with the boundary wall about different direction contacts to the collision. The rotary drillstring interaction with the drilling fluid outside,it forms a complex nonlinear fluid-structure interaction system.For the drillstring to fluid-structure interaction analysis's calculation of the workload is very great,therefore, this article to carry out the analysis of drillstring dynamics method for solving research. First,considering the drillstring in the wellbore's structure and working conditions the otary drillstring is scattered to several beam elements along axial line.The hydraulic pipelines is scattered to several equal long three-dimensional hydraulic pipelines fragment. The annular flow is scattered to random eccentric annular flow fragment.Every fluid fragment is also scattered to tetrahedron and hexahedron grid.The three-dimensional numerical model is established about the fluid–structure interaction dynamic analysis of rotary drillstring in shaft.The second, the equations of the structure dynamics, fluid equation of continuity and momentum equation are coupled. The method about the fluid–structure interaction dynamic analysis is proposed. As the actual project there is a large area of the contact problem,using the traditional iterative algorithms in the solution of nonlinear dynamic equations about the rotary drillstring in shaftis is time-consuming and calculate the amount of amazing.This article is based on the original method to unite the unknowns of the equation that the reduction of degrees of freedom to reduce the iterative steps and reduce the convergence workload,to increase operational efficiency.Through examples of calculation verified the improved accuracy of solution method and feasibility.At last,in order to solve the problem great quantity element number of the hydraulic pipelines and annular flow and the disability of the PC machine, the characterization database about the hydraulic pipelines and the annular flow is established. The database is able to automatic record and extract the fluid analysis result of different flow fragment and different technological parameters.At the same time through different circumstances annulus eccentricity of a large number of spiral flow calculation, It is revealed that the variable rule about the eccentric annulus fluid flow characteristics and interfacial force with the speed and eccentricity,on this basis construct a function of fluid flow field units and through simulation,compared verify the correctness of the constructor.At this point we can not characterize the database through the fluid extraction results, but directly call the function of fluid flow field is solved,the greater the improvement of the limits of the computational efficiency of the coupling operation.This study results could be provide methods calculation.for the Fluid-structure interaction analysis problem in oil drilling engineering and chemical mechanical coupling, the solving of contact problem in petroleum chemical industry equipment.