Safety Analysis Of Running Expansion Pipe In Horizontal Wells

The introduction of expansion tube subsidy technology in China has solved the problem of casing damage in complex wells.However,as horizontal wells have gradually become a hot topic in recent years,the problem of failure risk in the application of expansion tube subsidization technology in horizontal wells has become more and more prominent.To this end,this paper analyzes the safety of swell pipe subsidence in horizontal wells,and aims to provide a basis for analysis of swell pipe subsidence in horizontal wells.Firstly,a theoretical analysis of the safety of the downstream of the expansion pipe is conducted.A full-section trajectory fitting and well body parameters analysis are performed for horizontal wells.The micro-segments of the expansion pipe are established,and the force analysis of each micro-segment is carried out with the help of tribological theory to superimpose the influence of frictional force,so as to obtain the total value of frictional resistance of the expansion pipe in the lowering of the whole well section.The mechanical model of the expansion tube is established,and the force and deformation of the tube column in the whole well section are analyzed with the help of the theory of material mechanics and tube column mechanics.Secondly,ANSYS/ABAQUS simulation software was used to analyze the safety of the expansion pipe from the aspects of down-entry passability and reliability.A 30 m threaded expansion pipe was created,and the stress and deformation clouds of the pipe in the whole well section and the friction curves of the inclined section at different curvatures were simulated to determine the downward passability of the pipe.Further strength check analysis was conducted on the special connection threads used in the expansion pipe to determine whether the concentrated stress value at the maximum deformation of the connection threads exceeded the strength limit,and the tensile and compressive stresses were also applied to simulate the yield limit and tensile limit of the connection threads to determine the reliability of the expansion pipe down-entry.Finally,combined with the necessary indoor experiments,the negative effects of bending,tensile pressure,sealing rubber parts,expansion,bearing pressure and other loads on the expansion pipe were quantitatively evaluated,and then the reliability of the expansion pipe lowering into the horizontal well was verified.The results of the study showed that the axial bending deformation reached 623 mm and the maximum stress 257.31 MPa when the expansion tube was lowered into the slanting section,which was the maximum stress and deformation in the whole well section,but none of them exceeded the material yield limit;The frictional resistance of the expansion tube in the inclined section increases with the increase of the radius of curvature.After entering the horizontal section,the friction resistance reaches the maximum at the depth of 2693.5m in the horizontal section,which is about 6.8t.The maximum stress of the connection thread at the maximum deformation of the expansion pipe was 186 MPa,which did not exceed the allowable stress range of the thread;when a stress of 352800 N and a tensile force of 519400 N were applied to both ends of the connection thread,the thread reached the yield limit and the tensile limit respectively.