Thermo-hydro-mechanical modeling of carbon dioxide injection for enhanced gas-recovery (CO2-EGR): a benchmarking study for code comparison

Abstract

The objective of this paper was to investigate the THM-coupled responses of the storage formation and caprock, induced by gas production, CO 2 -EGR (enhanced gas recovery), and CO 2 -storage. A generic 3D planer model (20,000 9 3,000 9 100 m, consisting of 1,200 m overburden, 100 m caprock, 200 m gas reservoir, and 1,500 m base rock) is adopted for the simulation process using the integrated code TOUGH2/EOS7C-FLAC3D and the multi-purpose simulator OpenGeoSys. Both simulators agree that the CO 2 -EGR phase under a balanced injection rate (31,500 tons/year) will cause almost no change in the reservoir pressure. The gas recovery rate increases 1.4 % in the 5-year CO 2 -EGR phase, and a better EGR effect could be achieved by increasing the distance between injection and production wells (e.g., 5.83 % for 5 km distance, instead of 1.2 km in this study). Under the considered conditions there is no evidence of plastic deformation and both reservoir and caprock behave elastically at all operation stages. The stress path could be predicted analytically and the results show that the isotropic and extensional stress regime will switch to the compressional stress regime, when the pore pressure rises to a specific level. Both simulators agree regarding modification of the reservoir stress state. With further CO 2 -injection tension failure in reservoir could occur, but shear failure will never happen under these conditions. Using TOUGH-FLAC, a scenario case is also analyzed with the assumption that the reservoir is naturally fractured. The specific analysis shows that the maximal storage pressure is 13.6 MPa which is determined by the penetration criterion of the caprock.

Worldwide Status of CCUS Technologies and Their Development and Challenges in China

“…Unlike the CO 2 -EOR technology, CO 2 -EGR technology is still at the pilot-scale stage. Its efficiency is highly dependent on reservoir type, temperature and pressure conditions, heterogeneity, production strategy, and so on [55][56][57][58][59][60]. For some CO 2 -EGR projects, the gas recovered can reach 10%, while other projects have seen less or no enhancement [61][62][63].…”

Numerical Simulations of Enhanced Gas Recovery at the Załęcze Gas Field in Poland Confirm High CO2Storage Capacity and Mechanical Integrity

“…However, only simplified hydro-mechanical numerical simulation models, e.g. for benchmarking purposes, have been published on EGR operations (Gou et al, 2014;Hou et al, 2012). As the complex geology in the Załęcze natural gas field requires more sophisticated numerical models to be employed, we implemented coupling strategies using complex hydro-mechanical models with numerous geological faults from the reservoir up to the regional scale in order to account for vertical displacements as well as reservoir, caprock and fault integrity.…”

Carbon dioxide injection and associated hydraulic fracturing of reservoir formations

“…Potential areas for CO 2 storage include depleted oil and gas reservoirs, coal bed seams and deep saline formations. Also, the environmental and geo-mechanical benefits of CO 2 injection and storage have been extended to processes such as enhanced oil recovery (EOR) (Bachu et al, 2004, Godec et al, 2013, Gozalpour et al, 2005 enhanced gas recovery (EGR) (Al-Hashami et al, 2005, Hou et al, 2012 and enhanced coal bed methane production (ECBM) (Pini et al, 2011, Zhang andSong, 2012).…”

“…Thermal effects including changes in in-situ reservoir temperature arising from heat transfer/exchanges between the injected CO 2 and the formation, contribute to the dynamics of underground activities (Hou et al, 2012, Norden et al, 2012, Singh et al, 2012. Changes in reservoir temperature are dependent on the geological structure and variations in rock thermal conductivity (Norden et al, 2012); some aspects of Joule-Thompson cooling (JTC) and viscous heat dissipation (VHD) are illustrated in Singh et al (2012), while in Hou et al (2012) the thermal process is incorporated with hydro-mechanical processes for the prediction of reservoir responses.…”