On the suitability of premium OCTG tubing connections for CCS CO2 injection wells – a full scale physical evaluation

Abstract

Carbon Capture and Underground Storage (CCS) is a rapidly emerging solution to significantly reduce CO2 emissions into the atmosphere. CCS aims to capture CO2 at the emission source and then transport it to an underground permanent storage location. Wells will be used to inject CO2 into these storage locations. The wells are constructed using casing and tubing strings, similar to conventional oil and gas wells. Because the downhole conditions in CCS wells can differ significantly from the conditions in conventional oil and gas wells, suitability of the components needs to be verified. This study addresses the suitability of premium threaded connections for casing and tubing tubulars for CCS wells. An experimental program was executed during which a connection and small-scale samples were exposed to realistic downhole conditions as can occur in CCS wells. No difference of sealability or surface degradation was observed between the tests performed with CO2 at low temperature and tests performed with nitrogen at higher temperatures. Based on these results it is proposed that premium OCTG connections can be used for CCS service, provided the materials are suited for CCS service.