Mechanical Characteristic Analysis And Working Behavior Simulation Of Completion Packer System In High Pressure Oil And Gas Wells

Packer is a key downhole tool in well testing and completion.In recent years,abnormal setting and failure of packer often occur during the process of high temperature and high pressure deep well completion.In order to find out the failure reason of packer more accurately,draw the performance curve of completion packer,and carry out the mechanical characteristics analysis and working behavior simulation research of high pressure oil and gas well completion packer system.Taking the 7-inch THT permanent packer commonly used in well completion operation as the research object,the safety and reliability of the packer are studied from the overall point of view of the packer system by combining theoretical research and numerical simulation.Considering the nonlinear characteristics of material,geometry and contact of completion packer system,a nonlinear material model is established by using Mooney-Rivlin strain energy function based on finite element theory to deal with the problem of difficult convergence caused by geometric and contact nonlinearity.A three-dimensional finite element model of THT packer was established to investigate the stress distribution of key components of the packer under normal setting load and critical load.The influence factors of sealing performance and anchoring performance of the packer were studied by using control variable method.The failure mode,failure criterion and sensitivity index of packer system considering casing are proposed.Based on the failure theory of packer system,the drawing method and application of packer performance envelope curve are studied.The results show that:there is a good sealing state between the three rubber cylinders and the casing of THT packer,the contact stress between the rubber cylinders and the casing is not uniform,the change from the loading end to the constraint end is approximately linear decreasing,the contact stress of the upper rubber cylinder is the largest,the middle rubber cylinder is the second,and the lower rubber cylinder is the smallest.With the increase of the number of rubber cylinders,the contact pressure of rubber cylinders decreases in turn along the direction away from the compression end;the contact pressure of rubber cylinders decreases nonlinearly with the increase of friction coefficient and material hardness.The contact stress distribution between the slips and the casing of THT packer is uneven,and the contact stress between the slips far away from the wedge and the casing is obviously smaller than that near the wedge.When the top angle of slip teeth is 80 degrees(compared with 70 degrees and 90 degrees),it can not only ensure that the slip is firmly anchored on the casing,but also avoid excessive plastic deformation of slip.When the angle of slip teeth is 70 degrees(compared with 60 degrees and 80 degrees),it can not only ensure that the casing will not be damaged because of the slip biting too deep,but also obtain good anchoring performance.Based on the failure criterion of packer system,the drawing method of packer performance curve and its application method in operation are obtained;The results show that the simulation results of the packer system are in good agreement with the engineering practice.The application of the system based on the system angle makes the packer design and use safer.