Abstract

Despite significant advancements in rubber finite element analysis (FEA), rubber modeling remains to be a challenge, due to incompressibility, large deformation, viscoelasticity, permanent set, and thermal aging. These challenges become more acute for rubber applications in oil and gas industry under high pressure and high temperature (HPHT) conditions. In this work we focus on two specific topics in rubber modeling under HPHT conditions, rubber failure criteria and validation of rubber FEA for a quasi-static loading. Taking advantage of a comprehensive experimental program [1] which studied the extrusion-resistance performance of of four different ISO3601-1 sized O-rings made from a single batch of rubber. The study was conducted at 400°F when subjected to three extrusion gaps, at squeezes of 4%, 10%, and 15%. A total of 160 tests were performed in which the pressures required to extrude the O-rings were measured. Using these data, we evaluated four different rubber failure criteria (strain energy density, maximum principal strain, maximum principal stress and maximum shear stress criteria, respectively) and determined the most applicable failure criterion for these applications. As the physical measurements from the O-ring test program showed that rubber properties have certain degree of variabilities, so the extrusion tests for O-rings with the same nominal size have a statistical distribution. This statistical variability dictates that validation of rubber FEA should be performed in a statistical sense. Our rubber FEA approach is validated through the large-scale O-ring experimental observations. The validated rubber FEA approach has been successfully applied in much more complicated sealing systems, including packer elements for downhole fluid isolations [2]. Reference [1] Zhong, A., Glaesman, C. (2020), O-Ring Extrusions under High Pressure High Temperature Conditions, 198th Technical Meeting of the Rubber Division, ACS Virtual Technical Meeting, October 20-22, 2020 [2] Zhong, A, Dockweiler, D. (2020), Learning Cycle-based Project Management and Its Application, SPE 201515, 2020 SPE Annual Technical Conference and Exhibition, (virtual) October, 2020