Dissolution Phase Diagram in Radial Geometry

Abstract

Fractures play an important role as flow paths in porous media. When an undersaturated reactive fluid is flowing in a fracture, the dissolution process will alter the flow paths locally. Dissolution patterns grow slowly, but they may lead to a dramatic reorganization of the flow. Here, we study dissolution in a radial geometry, which is relevant for a number of practical applications, e.g., the acidization of oil reservoirs. Different dissolution patterns are presented in a phase diagram with the Péclet and Damköhler numbers as parameters. We also analyze quantitatively the density of wormholes and the relation between the aperture roughness and the ramified patterns.

Transitions of Dissolution Patterns in Rough Fractures

“…For R 0 > nγ 2 l t , although the system size is large enough to develop instability, the ratio γ is large enough for reactive fluid to dissolve the whole system uniformly and to produce uniform patterns. Besides, the values of l f for the six uniform dissolution cases (Table S1 in Supporting Information S1), ranging from 4.06 to 8.11 cm, are all larger than the system size 3.75 cm, which is also both consistent with the model predicted by Da u and Da u,1 (Starchenko & Ladd, 2018;Xu et al, 2020).…”

“…The boundary curve Da u,1 in (b) is predicted by Equation8with n = 2 and <b 0 >/ R 0 = 1/200(Szymczak & Ladd, 2009) Detwiler et al (2003). performed dissolution experiments in rough fractures and observed a wormhole dissolution pattern at Pe = 54, Da = 0.018 (v = 0.029 cm/s) and a uniform pattern at Pe = 216, Da = 0.0045 (v = 0.116 cm/s), which can be described by our phase diagram Xu et al (2020). performed dissolution experiments in radial Hele-Shaw cells.…”

“…Given that the flow geometries (fractures) used in these existing works are similar to our study, the parameters γ 1 = 4 and γ 2 = 35 in Figure 5 are also used in the model prediction shown in Figures 6a and 6b (the red and black solid curve, respectively). The curve Da u,1 in Figures 6a and 6b is predicted respectively with the parameters in the experiments with <b 0 >/R 0 = 1/533 and n = 1 (Detwiler et al, 2003;Xu et al, 2020) and the simulations with <b 0 >/R 0 = 1/200 and n = 2 (Szymczak & Ladd, 2009).…”

Dissolution Hotspots in Fractures

“…This sharp front, however, is not smooth (labeled with "1" Figure h), as evidenced by the single peak (labeled with "1") of the curve 2j. Such a dissolution front is different from the observed compact dissolution pattern in Hele-Shaw cells (Xu et al, 2020), which may be attributed to the effect of surface roughness. For the highest  263.7 E Pe considered (Figure 2a), on the other hand, we observe a uniform dissolution pattern that the NaCl crystal tend to dissolve everywhere.…”

Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

“…where l R = Dc in kh 0 . Typically, to analyze dynamic processes that are governed by flow conditions and reaction rates a set of dimensionless numbers is defined (Soulaine et al, 2017;Starchenko and Ladd, 2018;Xu et al, 2020). This study is relevant to the case in which the flow rates are relatively low and the work is focused on competition between reaction and transport.…”