Comparison of Leakage Characteristics of Viton and Polytetrafluoroethylene Seals in Gas-Lift Valve Applications

The present research article focuses on comparing the leakage characteristics of Viton and polytetrafluoroethylene (PTFE) seals used in enhanced oil-recovery system. The objective of the study is also to validate if each sealing material met the stringent gas leakage requirements of less than 2 SCCM as required by several enhanced oil recovery systems. The present effort mainly deals with the gas-lift valve barrier check valve applications. The article describes the development of a high-pressure (HP) test rig for measuring the performance of seals in barrier check valves. The rig is capable of measuring valve leakage at pressures up to 10,000 psi with either gases or liquids. A boost pump is employed for achieving pressures greater than 2000 psi (typical nitrogen bottle pressure). Rig validation tests were conducted on a check valve that is part of an injection-pressure-operated (IPO) gas lift valve. A test chamber was fabricated to contain the check valve and was mounted inside the enclosure to evaluate the performance of each sealing material and validate the rig capabilities using water and nitrogen as the working fluid. Finite-element analysis (FEA) on each sealing composition under 100 and 10,000 psi were performed to determine contact pressures and identify appropriate contact pairs at each pressure differentials. It is observed that a brand new PTFE seal never seals efficiently unless it is subjected to a pressure sweep. Viton seals appeared to be insensitive to the pressure sweep as it effectively sealed for the entire pressure range.