Role of partial miscibility on pressure buildup due to constant rate injection of CO₂ into closed and open brine aquifers

Abstract

[1] This work extends an existing analytical solution for pressure buildup because of CO 2 injection in brine aquifers by incorporating effects associated with partial miscibility. These include evaporation of water into the CO 2 rich phase and dissolution of CO 2 into brine and salt precipitation. The resulting equations are closed-form, including the locations of the associated leading and trailing shock fronts. Derivation of the analytical solution involves making a number of simplifying assumptions including: vertical pressure equilibrium, negligible capillary pressure, and constant fluid properties. The analytical solution is compared to results from TOUGH2 and found to accurately approximate the extent of the dry-out zone around the well, the resulting permeability enhancement due to residual brine evaporation, the volumetric saturation of precipitated salt, and the vertically averaged pressure distribution in both space and time for the four scenarios studied. While brine evaporation is found to have a considerable effect on pressure, the effect of CO 2 dissolution is found to be small. The resulting equations remain simple to evaluate in spreadsheet software and represent a significant improvement on current methods for estimating pressure-limited CO 2 storage capacity.

Numerical simulations of pressure buildup and salt precipitation during carbon dioxide storage in saline aquifers

“…1(a). Meanwhile, 42 the injection of dry supercritical CO 2 will displace the resident brine immiscibly, combined 43 with the evaporation of water, which may eventually cause the aqueous phase dry-out and salt 44 precipitation near the injection well [7][8][9][10][11][12][13][14]. The spatial size of precipitation region is just a 45 small fraction of the plume.…”

Heat transport and pressure buildup during carbon dioxide injection into depleted gas reservoirs

“…Therefore, it can be shown that α r = (1 − θ r )θ −1 r c r . Mathias et al (2011a) previously assumed θ r = 0.8 and α r = 4.5 × 10 −10 Pa −1 . This corresponds to a value of α r = 1.125 × 10 −10 Pa −1 .…”

“…Furthermore, although there are large changes in pressure resulting from the injection process, for constant mass injection rates, these mostly occur at the beginning of injection (cf. Mathias et al 2011a). Consequently, when considering the development of analytical solutions for heat transport in this context, argue that one can additionally assume that (i) the presence of the CH 4 can be ignored and (ii) the pressure distribution is steady state.…”

“…This in turn would give rise to lower pressure gradients (cf. Mathias et al 2011a) and hence less Joule-Thomson cooling.…”

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

“…The solid lines and dashed lines represent results from the analytical solution and numerical solution, respectively. The high gas saturation around the injection well, often referred to as a dry-out zone (Mathias et al 2011), is due to the vaporization of the residual water saturation by the injected CO 2 . A CH 4 bank with about 22 % gas saturation in front of the CO 2 plume develops.…”