Nonlinear Simulation Of Well Testing Packer System

The packer for testing is the key tool to seal the downhole pressure in the testing operation,and the safety of its application in high temperature and high pressure wells is self-evident.At present,the nonlinear mechanical behavior,failure mode,failure criterion and seal integrity of the packer are not studied from the perspective of system.Therefore,the nonlinear simulation analysis and performance envelope of the packer for testing are studied.Taking the RTTS packer commonly used in testing as the research object,considering the nonlinear characteristics of material,geometry and contact,the nonlinear material model is established with Mooney Rivlin strain energy function based on the nonlinear finite element theory.The hybrid grid,nonlinear adaptive region and penalty stiffness algorithm are used to deal with the difficult convergence problems caused by geometric and contact nonlinearity.The three-dimensional finite element model of RTTS Packer is established,and the influence factors of sealing performance and anchoring performance of Packer are studied by using the method of control variables.From the perspective of packer system,the mechanical properties of sealanchor system are studied and compared with the mechanical properties of independent components.The failure mode and failure criterion of packer system considering casing are proposed.In addition,the sensitivity coefficient index of rubber is put forward.Based on the failure theory of packer system,the drawing method and application of packer performance envelope are studied.It is found that the equivalent stress and contact pressure of the rubber increase nonlinearly with the linear increase of the setting load;with the increase of the number of rubber,the contact pressure of the rubber decreases in turn along the direction away from the compression end;the contact pressure of the rubber decreases nonlinearly with the increase of the friction coefficient and the hardness of the material.The equivalent stress of casing and slip insert teeth is the basis of judging slip anchoring performance and safety.When the cone angle of slip is 12 °(compared with 10 ° and 14 °),and the tooth angle is 60 °(compared with 70 ° and 80 °),the comprehensive anchoring performance of slip is better;when the anchoring performance is satisfied,the comprehensive performance of double row double insert bit slip is better than that of double row single insert bit slip.The simulation results of packer seal-anchor system are obviously different from the simulation results of independent components.From the system perspective,a failure evaluation criterion of packer system based on the integrity of casing is proposed and evaluating the performance of rubber with the sensitivity coefficient of rubber.Based on the failure criterion of packer system,the drawing method of packer performance and its application in operation are obtained.The finite element simulation results of the system considering nonlinearity are basically consistent with the engineering practice.The application of the Packer seal integrity evaluation system based on the system makes the Packer design and use more safe.