The Analysis On The Force And Deformation Of Tubing String In Three-dimensional Curved Well Bore Based On Elastic Rod Theory

Because of the tubing string got force from different value and direction,it's impossible to make the theoretic calculation and practice fit entirely.All methods about the analysis on the force and deformation of tubing models are simplified.It's can't validate and explain the series problems in drilling operation when the considerations of factors are simplistic overly.So a ideal model are widely used in practices guidelines,not only fit the reality but also efficiency.The purpose of this research is try to establish a new model of tubing force and deformation—based on the theory of elastic rod in the force and deformation of Tubing model,combined with the tubing mechanics and emerging theory of elastic rod was used to simulate the strands of DNA,set up a series methods to simulate the force and deformation of Tubing in the 3D condition and verify some problems which could not explain by existed models.The tubing with large deformation state in higher length although it has rigid materials,and the description of elastic rod is about bent lever which has severe deformation and length,the similarity provides a basis for the combination of these two.Compared with existed methods,the significant feature of elastic rod is which establish the analyzing model in 3D condition directly and take consideration of the problem about the coupling in torque and stress.The studies of this dissertation focus on following aspects:(1)Establish a balance equation based on the theory of elastic rod,take advantage three kinds of way to solve this equation and optimize the proper one.(2)Establish a model which was used to describe the force and Deformation of single-span tubing in different boundary conditions and distributed force.Through analyze and contrast the result between the theory of elastic rod and bending beam method,demonstrate the validity of the theory of elastic rod and find the reason of the differences between the two ways.(3)Establish a model which was used to describe the force and deformation of multi-span tubing in different boundary conditions and distributed force,and combine with the in-door experiment device to verify the variation trend of torque and axial force with different hole radius,corners,string size,working conditions.(4)Through the theoretical calculation results to verify if the torque could effect on the axial force and stress.In the preliminary work of try to combine the elastic rod theory with drill string mechanics has demonstrated that elastic rod was able to simulate and analysis the deformation and the force of tubing as a new model.Due to the principal axis system tangent to the center line of the string,it's not appear to approximation error on coordinate in solving the problem of large deformation for the single span string.Through the theoretical simulations of indoor device,that the results of simulation by elastic rod model is more accurate than bent beam model under the circumstances of three-dimensional and wall constraint on tubing string.At last,the torque at the end of the string will affect the normal pressure and change the axial force further.