Optimization Design Of Packer Structure Based On Separate Pumping Test

At present,with the vigorous development of the national basic geological survey,the packer is more and more used in the stratified pumping test.After a period of application and improvement,it has been able to complete pumping test from several layers to dozens of layers,and the utilization rate of drilling has been greatly improved,and the obtained hydrogeological parameters are more accurate.However,during the use of the packer,there are some problems such as the rubber sleeve is vulnerable,sealing failure,and the low inflation rate.In this paper,the structure of the packer is optimized by structural design and theoretical calculation and numerical simulation methods.The structural design is based on an inflatable expansion packer developed by Hydrogeology and Environmental geology survey center,adding a protective sleeve and a two-stage sealing unit.Theoretical analysis includes the calculation of the setting pressure and the analysis of the setting process.Calculating the setting pressure required according to the actual working process and nitrogen consumption;The setting process is divided into two stages: front contact and post-contact.Before the contact,due to the nonlinear characteristics of the geometric material and the rubber material,the stress-strain relationship cannot be analyzed by elastic mechanics.Therefore,Yeoh hyperplastic rubber constitutive model with the three-parameter is adopted,analyzing the deformation characteristics of the rubber sleeve combined with finite element method;In the post-contact stage,due to the small amount of deformation,the formula of the setting condition is derived by classical mechanics.In the numerical simulation part,due to the axisymmetric structure of the packer,only a quarter arc is simulated.Through the static module of ANSYSworkbench,modelling the length,thickness,friction coefficient,internal pressure and structure of different rubber sleeve.The analysis of the setting effect is based on the contact pressure of the surface of the rubber sleeve,supplemented by the deformation of the contact surface.The model of the packer used for the simulation includes: the length of the rubber sleeve is 300 mm,400mm,500mm;the total thickness of the rubber sleeve is 14 mm,16mm,18mm;the friction coefficient between the rubber sleeves is 0.5,0.6,0.7;the given internal pressure is 5MPa,10 MPa,15 MPa,20 MPa and packers with single and double enclosed unit.Optimized to obtain an optimal solution,when the length of the rubber cylinder is 500 mm,the total thickness of the rubber cylinder is 16 mm,the friction coefficient between the double-layer rubber cylinder is 0.5,and the internal pressure is 10 MPa,and the packer with double enclosed unit,there will be having the best setting effect.At this time,the average contact pressure of setting is 8.0298 MPa,which is 0.03 MPa higher than that of the single-stage rubber sleeve,and the total radial sliding distance is 2.824 mm,which is 0.429 mm more than the single-stage rubber sleeve.