Advances in sour gas injection for enhanced oil recovery-an economical and environmental way for handling excessively produced H2S

Abstract

Proper handling of produced sour gas is a big challenge for operating companies due to the serious environmental and technical problems caused by H2S. Among various sour gas processing methods, reinjection into reservoirs is a cost-effective and environmentally-friendly technique that not only enhances oil recovery but also allows underground storage of H2S. The high safety requirements for working with toxic H2 S have suppressed extensive experimental studies, hence sour gas injection has not been adequately investigated and implemented in laboratory compared to other enhanced oil recovery (EOR) methods. Existing studies show that sour gas injection with high H2S content can bring about higher incremental oil recovery than CO2 or CH4 injection due to the highly miscible nature of H2S with a significant reduction of minimum miscibility pressure (MMP) and interfacial tension. Mineral dissolution as well as sulfur and asphaltene precipitation might occur as consequences of sour gas induced reactions, thus causing technical challenges such as low injectivity, formation damage, and poor sweep efficiency, but contrary observations were also reported. In addition, the economics of sour gas injection for EOR depends on several critical factors, such as H 2 S content in crude oil, sulfur price, and environmental impact. Overall, sour gas EOR presents far more challenges than other EOR methods, deserving full-fledged and in-depth investigations. This review comprehensively assessed the performance of the sour gas EOR method by integrating the results of laboratory experiments, simulation, field test studies, and economic analysis.