Design Validation of Critical Wellhead and Tree Seals to Operate in Cryogenic Condition (-75°C) Throughout the Life of Carbon Capture and Storage (CCS) Injection Wells

Abstract The global drive toward decarbonization demands significant energy sector transformations to meet net-zero targets. Carbon Capture and Storage (CCS) projects aim to safely store CO2 underground. However, but technical challenges persist, particularly due to especially as CCS is not yet common and no the lack of established standard for critical well components. Wellhead and tree elements must withstand cryogenic temperatures from rapid CO2 depressurization and maintain integrity throughout injection life. This paper validates the tubing hanger and gate valves for long-term performance in Southeast Asia's offshore CCS injection wells. During CO2 injection, surface temperatures typically range from 20°C to 25°C, rising to 30°C during well shut in. However, during TRSV operating cycle function testing, rapid depressurization can occur. TRSV isolates the wellbore from surface equipment, and if tubing pressure releases quickly, CO2 expansion causes surface temperatures to drop to −52°C due to the Joule-Thomson effect. Therefore, tubing hanger and gate valves are validated for K and U temperature classes (−60°C to 121°C) with material class HH, meeting API 6A standards and supporting future projects requiring combination of extreme low and high temperature rating. API 6A PR2F validation for the tubing hanger includes load cycling, internal pressure, and thermal cycling seals tests. Gate valves undergo force and torque measurement, dynamic testing, and gas body/ seat tests. Additional resilience test was performed at −75°C to verify the composite seal limitations. For this, a custom setup was engineered for thermal cycling from −75°C to 121°C. Advanced PTFE and PEEK materials were used for tubing hanger seals ensuring reliability. The design validation confirmed that tubing hanger and gate valves met performance criteria for CCS operations under cryogenic conditions. The tubing hanger successfully passed all API 6A PR2F tests, maintaining structural integrity and pressure retention across the K+U temperature range (−60°C to 121°C). The gate valves also passed, completing 200 cycles at various temperatures and pressures, with torque values within specified limits. During gas body and seat tests, they endured temperatures from −60°C to 121°C and pressures up to 5,000 psi. The additional resilience tests conducted at −75°C showed successful results for tubing hanger and gate valves, with PEEK and PTFE seals successfully maintaining pressure without leakage. It is noteworthy that the testing process required significant time due to equipment preparation and temperature reduction to −75°C. The results achieved by the tubing hanger and gate valves, validated under a combined temperature class K and U (−60°C to 121°C), represent a forefront in the industry. The validation confirmed that both components maintain full reliability even after exposure to extreme cryogenic conditions at −75°C. This study establishes a benchmark for performance in CCS projects, ensuring operational integrity and safety in Southeast Asia's offshore environments.