Simulation Study On Mechanical Behavior Of Pipe String In Overhaul

the main purpose of simulating highly deviated wells overhaul work string mechanics behavior is to establish the numerical modeling theory and simulation technology about full well workover string mechanics of highly deviated well and investigate the application methods. the core technical method is finite element method. Based on general function of ANSYS software, developed highly deviated wells overhaul mechanics simulation technology and improved the efficiency of the numerical solution methods.First of all, researched on the modeling technology of highly deviated overhaul operations wells and work strings, based on the input data of borehole trajectory and workover string, three-dimensional trajectory and string visualization is achieved.Secondly, analyzed on the calculation algorithm about sticking point, back-off, fishing and stuck freezing.(1)For the prediction of sticking point location:to the specific borehole trajectory and string combination, based on the changing rule of string lift force in three-dimension nonlinear contact situation, the judge mechanism of sticking point location is established, and numerical simulation method of high deviated well sticking point prediction is generated.(2)For the parameter calculation of back-off and fishing technology:on the basis of lift force simulation, the recommended shackle location is on the neutral point, which provides theoretical basis for the reliable shackle.(3)For stuck freezing parameter calculation: for ordinary packer strings and multistage packer strings, the numerical simulation method is established to calculate the stuck freezing force. the stuck freezing force is calculated, based on actual working conditions to determine the string combination, packer unset force and its working mechanism, build simulation model and implement the calculation of the changing axial force, determine the lift force (stuck freezing force) on the critical condition.Finally, string physical quantities of each element and the load situation of each node are gained through simulation post-processing. Comparing simulation results with the field measured data shows that the model generated from the simulation can reflect main force behavior of string, which can help us design and evaluate the high deviated well workover project as well.