Research Of Contact Force And Fluid Simulation Based On Coiled Tubing Cleaning

With the improvement of coiled tubing operation technology,more attention has been attached to the maintenance of coiled tubing devices.Cleaning and discharging the impurities in the coiled tubing is essential to prevent tube from corrosion.Domestic status in this field is mostly in engineering practice.The cleaning is not sufficient after simple flushing or rinsing the impurity attached to the inner wall of the coiled tubings like mud,sand and acid substances.The corrosion of the coiled tubings will still happen.Furthermore the liquid remaining on the inner wall of the coiled tubing causes the burst below 0℃.The method of nitrogen gas purging also cannot conform to the standard of cleaning.This study proposes a new method for cleaning coiled tubings,and designs the high pressure gas cylinder according to it.Then according to the new method of cleaning tubings,the 3D model of rubber plugs and coiled tubings are established,and the non-dimension parameters δ and ζ are defined.A finite element analysis of the contact process is carried out by ANSYS which considers the material nonlinearity and the status nonlinearity to predict the contact force.The effect of interferences and thicknesses of cylindrical rubber and interferences of spherical rubber plugs to the cleaning is analyzed.A fluid model in turbulent status is established by FLUENT.UDF module combined with dynamic mesh is used in this FLUENT model.For predicting the cleaning process,the impact of the interference of cylindrical rubber on fluid motion is analyzed.The result obtained in this study shows that the influence of the interference of the cylindrical rubber on the contact pressure decreases with the increase of the interference.The influence of the thickness on the contact pressure is greater than the interference.This relationship is almost the same on different differential pressure.A linear relationship between the differential pressure and contact force can also be observed.In fluid simulation,as is shown in the calculation result of fluid pressure,velocity and turbulent energy,a small interference lead to a small energy loss and a smooth movement of cylindrical rubber.But it causes the insufficient cleaning.In the case of large interference,the energy loss is huge,the movement meet high resistance,the jam may occur,and the large interference will cause sharp wear.From the analysis,the interference have a great impact on cleaning process.5% interference can be a reasonable choice for cleaning.