Chapter Eleven - Enhanced gas recovery technologies aimed at exploiting captured carbon dioxide

Abstract

Enhanced gas recovery by injecting CO2 into producing unconventional natural gas reservoirs is considered a promising technology to both sequester CO2 and improve recovery of unconventional natural gas. Especially for coalbed methane and shale gas reservoirs, the CO2 enhanced coalbed methane (CO2-ECBM) and CO2 enhanced shale gas recovery (CO2-ESGR) have attracted more and more attentions in recent years due to the dual benefits. Advancing the understanding of complex multi-physical coupled processes in the presence of multiphase and multicomponent gases (supercritical CO2, gaseous CO2, and CH4, etc.) via laboratory experiments, theoretical model development and field validation studies are of great importance for the engineering application of the technology. This chapter introduces the knowledge involved in the whole process, including the mechanism of supercritical CO2 fracturing and the characteristics of CO2 (especially supercritical CO2) influencing the fracturing behavior, the competition adsorption behaviors of CO2/CH4 in unconventional gas reservoir, the multicomponent CO2/CH4 diffusion, and flow behaviors, the evolution of permeability of unconventional gas reservoir during the CO2 enhanced gas recovery process, and the sequestration mechanism and safety of CO2 geological storage. The objective of this chapter is to provide some insights to understanding the whole process of CO2 enhanced gas recovery and geological sequestration in unconventional gas reservoirs, especially in coalbed methane and shale gas reservoirs.