Experimental investigation of elastomers in downhole seal elements: Implications for safety

摘要

One of the multiple barriers that is installed in the downhole during drilling and completion is the liner hanger seal assembly. The liner hanger is used to engage the liner, connect it to the previous casing, and seal off with cement before a pressure test is performed. Verifying the sealability of the elastomeric element in a liner hanger is a critical factor for well integrity. In this study, the performance verification process and tests were conducted based on critical reviews of literature, current regulations, and applicable industry standards. The objectives of this experimental study are to develop testing protocols to investigate the performance of common elastomeric seals that are used in a liner hanger seal assembly. Ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) were selected for the tests because they are commonly used in downhole sealing systems. The results from the experiments revealed that the elastomeric seals did not exhibit any leakage when they were subjected to a pressure test of 40 psig (275.79 kPa) under normal conditions. The sealing performance of EPDM and NBR after surfactant degradation was not impaired for the test conditions used in this study. However, both elastomers failed the pressure tests and leaked when a mechanical defect was intentionally created and after exposure to carbon dioxide. The pressure cycling results showed that elastomers energization plays a critical role in maintaining their seal integrity. The results also showed that prolonging the pressure test duration from 30 to 60 min did not affect the elastomers performance.