Mechanical Behavior and Structure Optimization of Compressed PHP Packer Rubber

Abstract

One of the core tools of horizontal well-staged fracturing completion technology is the compressed packer. The sealing and stability of packer rubber are key factors affecting the safe exploitation of high temperature, high pressure, and deep, complex oil and gas resources. The phenomenon of low setting pressure and early setting failure frequently occurs due to the unreasonable sealing structure. Therefore, in this paper, the tensile test of dumbbell hydrogenated nitrile butadiene rubber (HNBR) samples is conducted, and the stress-strain data of HNBR were obtained. The finite element mechanical model (FEM) of compressed PHP packer is established with consideration of material nonlinearity, geometric nonlinearity and double contact nonlinearity by adopting large-scale finite element analysis software ANSYS Workbench, verified by measured test data. Based on the verified FEM, the mechanical behavior and sealing performance of the original rubber under different setting loads are simulated. The contact pressure and its distribution, deformation, compression stroke of rubber and the relationship between them and axial loads are obtained. The mechanical behavior and sealing performance of packer rubber under different heights, thicknesses, external bevel angles, loading modes and steel-rubber friction coefficients with and without outburst prevention devices are investigated systematically using a manual-graphical optimization trial method. Results show that the packer rubber with the height of 75 mm, external bevel angle of 45°, steel-rubber friction coefficient ranging from 0.10 to 0.15 and outburst prevention devices can achieve the largest contact pressure and best sealing performance by adopting the setting method of bidirectional loading.