Design and feasibility of acid gas reinjection with corrosion mitigation: A case study from Tahe Oilfield, China

Abstract

• First Acid Gas Injection Project in China: This study presents the first acid gas injection and geological storage project in China, targeting the Tahe Oilfield No. 2 Joint Station. It marks a significant step in addressing acid gas treatment challenges and reducing CO₂ emissions. • Compression+Propane Refrigeration Dehydration: The project employs a novel compression and propane refrigeration dehydration process, reducing the moisture content of acid gas to 2.613 g/Nm³, effectively preventing corrosion and ensuring safe transportation and injection. • Safe and Efficient Injection Process: The design includes emergency shutdown and venting systems to prevent H₂S leakage, with ground injection pressures ranging from 16.7 to 21.7 MPa. The injection process is optimized for safety and efficiency, ensuring long-term storage of acid gas. • Economic Viability: The acid gas injection solution is economically superior to traditional sulfur recovery methods, with a processing cost as low as 0.9 RMB/Nm³. The project demonstrates significant cost savings and environmental benefits over a 10-year evaluation period. • Environmental and Economic Benefits: The project eliminates the need for sulfur recovery, reducing CO₂ emissions and avoiding the production of non-marketable byproducts. It aligns with China's carbon reduction goals and offers a sustainable solution for acid gas treatment. • Technological Demonstration: As a pioneering project, it provides valuable engineering experience and technical data for future large-scale acid gas injection projects in China, setting a benchmark for environmental and economic performance. This paper presents a comprehensive overview of the pioneering acid gas reinjection and geological storage project implemented in China. The study uses acid gas dehydration via compression and propane refrigeration dehydration techniques to prevent corrosion, the water content in the acid gas mixture was effectively reduced to 2.613 g·Nm −3 . Two preventive measures, namely emergency shutdown and emergency vent combustion, were incorporated to mitigate the risk of sulfuretted hydrogen (H 2 S) leakage. The injection pressure for pure gas at the surface was carefully determined, ranging between 16.7 and 21.7 MPa. Simultaneously, the surface injection process, wellhead configuration, and pipe string design were developed. Two distinct methodologies were employed for pipeline leakage detection: an open optical path leakage detector and optical fibre pipeline leakage detection. This research encompasses an investment analysis of the project, the acid gas treatment cost per unit of the acid gas reinjection scheme can be as low as 0.9 CNY·Nm −3 , which is much lower than that in the station process modification scheme. The study shows that the acid gas reinjection technology has significant economic and environmental benefits, can effectively reduce CO 2 emissions and solve the acid gas treatment problems. The implementation of this project provides important engineering experience and technical data for large-scale acid gas reinjection projects in China and has an important demonstration role.

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