Injection, Flow, and Mixing of CO2 in Porous Media with Residual Gas

Abstract

Geologic structures associated with depleted natural gas reservoirs are desirable targets for geologic carbon sequestration (GCS) as evidenced by numerous pilot and industrial-scale GCS projects in these environments world-wide. One feature of these GCS targets that may affect injection is the presence of residual CH 4 . It is well known that CH 4 drastically alters supercritical CO 2 density and viscosity. Furthermore, residual gas of any kind affects the relative permeability of the liquid and gas phases, with relative permeability of the gas phase strongly dependent on the time-history of imbibition or drainage, i.e., dependent on hysteretic relative permeability. In this study, the effects of residual CH 4 on supercritical CO 2 injection were investigated by numerical simulation in an idealized one-dimensional system under three scenarios: (1) with no residual gas; (2) with residual supercritical CO 2 ; and (3) with residual CH 4 . We further compare results of simulations that use non-hysteretic and hysteretic relative permeability functions. The primary effect of residual gas is to decrease injectivity by decreasing liquid-phase relative permeability. Secondary effects arise from injected gas effectively incorporating residual gas and thereby extending the mobilegas plume relative to cases with no residual gas. Third-order effects arise from gas mixing and associated compositional effects on density that effectively create a larger plume per unit mass. Non-hysteretic models of relative permeability can be used to approximate some parts of the behavior of the system, but fully hysteretic formulations are needed to accurately model the entire system.

A model comparison initiative for a CO2 injection field test: an introduction to Sim-SEQ

“…These features add significant complexity when approximating the natural system, and challenges arise in dealing with boundary conditions. In addition, presence of methane has been confirmed in the brine, which can potentially exsolve and impact pressure buildup history and CO 2 plume extent (Oldenburg and Doughty, 2011).…”

Simulation of Three-Component Two-Phase Flow in Porous Media Using Method of Lines

“…As was shown in the previous section, numerical simulations of CO 2 injection into a reservoir containing CH 4 predict the accumulation of a CH 4 bank at the head of the CO 2 plume (Oldenburg and Doughty 2011;Battistelli and Marcolini 2009;Taggart 2010). The system in discussion can be differentiated into three regions (Hosseini et al 2012).…”

“…The development of the CH 4 bank ahead of the CO 2 has been explained as follows (Taggart 2010;Oldenburg and Doughty 2011;Hosseini et al 2012). As CO 2 is injected, it partitions into the gas phase and the aqueous phase.…”

“…As CO 2 is injected, it partitions into the gas phase and the aqueous phase. The initially dissolved CH 4 exsolves immediately and is then pushed ahead of the growing CO 2 plume leading to the development of a CH 4 bank (Oldenburg and Doughty 2011). Mathematically, the system is constrained to constantly enter and leave the two-phase region along the tie-lines representing the injection and initial compositions; therefore, the leading CH 4 bank is free from injected gas, CO 2 (Taggart 2010).…”

Evaluating impacts of CO2 and CH4 gas intrusion into an unconsolidated aquifer: fate of As and Cd

“…Blanco et al (2012) reported CH 4 levels as high as 6% in industrial emissions in Spain (generated by waste management); however, a study conducted by de Visser et al (2008), in agreement with the European Enhanced Capture (ENCAP) project, suggested a limit of 4% CH 4 in gas injection streams. CH 4 can also be present as a native gas prior to injection (Taggart, 2010;Oldenburg and Doughty, 2011;Hosseini et al, 2012). The production of methane by methane-producing bacteria is also a source of CH 4 within storage reservoirs (Leu et al, 2011).…”