Mechanical Analysis Of Flexible Drill String In Radial Horizontal Well

As a new stimulation technology,the drilling technology of flexible drilling tools in radial horizontal Wells has a great prospect in the future.Due to the technical requirements of radial horizontal Wells,radial horizontal well flexible drilling tools are different from the traditional horizontal drilling tools.Its own structure is mainly composed of hemispherical hinged flexible drilling pipe connected with each other,plus the guide pipe that plays a guiding role.In the process of drilling,there are hinge constraints between the flexible drill pipe and contact collision between the drill pipe and the guide pipe,so it is difficult to carry out reasonable modeling and simulation analysis of the flexible drill pipe.According to the drilling technology of flexible drilling tool in radial horizontal well,the topological structure of flexible drilling tool system in drilling process is analyzed in this paper.In this paper,the flexible drilling tool system,which is a typical closed-loop multi-body system structure,is studied as two subsystems: the guide pipe and the flexible drill pipe by cutting off the hinges.Through finite element simulation,the constraint of guide pipe on flexible drill pipe is transformed into the force constraint of linear spring.At the same time,for the collision contact between flexible drill pipe and guide pipe,this paper deals with this kind of variable topology problem by using continuous contact model through theoretical research.In this paper,several classical modeling methods of multi-body system dynamics are compared,and the Cartesian coordinate method based on point system is selected.The point-system Cartesian coordinate model of flexible drilling tool system is derived by using semi-recursive method,and the program of formalized modeling is completed.Aiming at the topological structure problems such as the upper limit of transmission between flexible drill pipes in flexible drill tools system,this paper derives the formula of velocity change when flexible drill pipes reach the rotational limit by referring to the discrete model method for dealing with contact collision in multi-body system analysis.By using the built-in integrator in Matlab,the integral control program corresponding to the integral is written,and the multi-body dynamics simulation of the flexible drilling tool system is completed.In order to verify the rationality of the model and algorithm established in this paper,the flexible drilling tool system was simulated under different working conditions,and the results were compared with the data in relevant literature.At the same time,from the point of view of engineering examples,the advantages and disadvantages of the self-programmed calculation presented in this paper are compared with the commercial software calculation,and it is concluded that the method presented in this paper has certain advantages when calculating large curvature radius and well deviation Angle.