Finite Element Simulation And Analysis Of Expansion Process Of The Solid Expansion Tube

In recent years,in order to achieve the purpose of avoiding water,Tahe Oilfield has raised the kick off point(KOP)to mudstone strata during the construction process.In order to solve the collapse problem of mudstone well wall,the traditional solution is to increase the hierarchy of the casing while the normal casing will not meet the production requirement.The solid expansion tube(SET)technique is used to stabilize the mudstone well to increase the size of the hole.It is necessary to research the expansion force during the construction process.Also,it is necessary to research the factors such as expansion rate,expansion tube material mechanical properties and tool structure parameters to provide theoretical basis for the expansion of the reasonable parameters.According to the actual condition of Tahe Oilfield,this paper used elastic-plastic mechanics to solve the problem.During this period,the entity expansion pipe finite element dynamic analysis model was established.After considering the boundary conditions,the central difference method was used to solve the equations of system.The expansion ratio,the yield strength,the borehole curvature,the expansion cone angle,the expansion rate and the coefficient of friction factors on the SET was also considered to calculate the expansion force.After the expansion process,through the analysis of the influence factors of the residual stress of the SET and the strength of the casing resistance,the compressive strength of the SET was simulated by the finite element method.According to the field operation parameters of the SET of Tahe Oilfield,the theoretical model was compared with the measured data,and the rationality of the model was verified.The research results show that at the beginning of the expansion process,the maximum equivalent stress occurs in the casing internal wall.With the moving of the expansion cone,the equivalent stress decreases and approaches the residual stress at the end of expansion.The expansion force will increase with the increase of the parameters such as the borehole curvature,the expansion rate,the friction coefficient and the material yield strength.Optimizing the expansion cone angle will decrease the friction in the expansion cone.Usually,the expansion cone angle of near the 10° can cause the minimum expansion force.The expansion velocity has little effect on the expansion process.Through the analysis of the influence factors of the residual stress and the strength of the casing collapse resistance,the casing collapse strength was simulated by the finite element method.The casing collapse strength is mainly affected by residual stress,the uneven thickness of wall and the inroundness are able to affect the casing collapse strength of SET.While the SET is not uniformly deformed and the residual stress is pretty large,the casing collapse strength will greatly reduce.The research results of this paper provide reliable theoretical support for the field application of the solid expansion tube technology.