Pore-Scale Modeling of Nucleation and Growth in Porous Media

Abstract

During the chemical interactions between fluid and minerals in different geological processes, it is of high importance to predict where secondary precipitates form in the porous rocks as it helps correctly predict the hydrodynamic properties of the porous media. The reactive transport models developed for this purpose need to account for the nucleation process which is probabilistic by nature. To our knowledge, the probabilistic nature of nucleation based on the classical nucleation theory has not been accounted for previously in reactive transport models. In this study, we develop a new probabilistic nucleation model and incorporate it into a pore-scale reactive transport solver to simulate the mineral nucleation and growth in the porous media. Simulations are performed for different supersaturations, growth rates, and flow rates using a single-component mineral reaction. Simulations show that initial supersaturations strongly affect the pattern of secondary precipitate formation. Higher initial supersaturations lead to more uniformly dispersed nucleation on all the grains, while the lower initial supersaturations result in more isolated patterns. Decreasing the growth rate favors the formation of uniformly dispersed nuclei, whereas higher growth rates cause more isolated nucleation. Injection of fluid with a higher velocity gives rise to more precipitation. Moreover, comparison of probabilistic and deterministic nucleation showed that the isolated nucleation patterns cannot be modeled using the deterministic approach. The results showed that permeability for the porous media is influenced by the pattern of secondary precipitate growth and it is demonstrated that generally, the permeability has a direct relation with the initial supersaturation and an inverse relation with the growth rate and the flow rate. Finally, the model was applied for simulation of calcite nucleation and growth on quartz grains. The calcite nucleation and growth exhibit similar behavior to those observed for single-species simulations.

Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

“…By contrast, uniform mineral growth around the grains represents a surface reaction-controlled process [ 74 ], whereby the chemical reaction rate limits precipitation and the pore space is altered homogeneously. Both spatial precipitation patterns have been observed in several laboratory [ 19 , 21 , 56 ] and numerical studies [ 18 , 80 , 81 ], investigating mostly calcite and barite precipitation in porous media. Preferential precipitation in regions of LFV can be explained by an undisturbed growth of minerals, whereby fluid shear stresses limit precipitation.…”

“…Hence, to predict the effect of precipitation especially on the hydraulic rock behaviour, an adequate characterisation of the spatial pore alteration pattern is crucial. Of course, the process of mineral nucleation and growth is complex and depends on more factors than solely the fluid flow velocity: the location of mineral precipitation is controlled by the chemical reaction regime, which depends on fluid chemistry [ 16 , 17 ], transport properties [ 18 , 19 ], mineralogy [ 20 , 21 ], temperature [ 22 , 23 ] and pore morphology [ 24 , 25 ]. Hence, in contrast to reactive transport simulations, the presented approach cannot examine the temporal aspect of precipitation, e.g., the clogging of pores near the inlet, as can be observed in pore-scale laboratory experiments [ 16 , 98 ].…”

“…In general, precipitation reduces the porosity, but the effect on transport properties may be either negligible or significant depending on the specific location within the pore network ( Figure 1 ). The spatial distribution of mineral nucleation and growth is complex and controlled by various factors including chemistry [ 16 , 17 ], transport properties [ 18 , 19 ], mineralogy [ 20 , 21 ], temperature [ 22 , 23 ] and pore morphology [ 24 , 25 ], whereby the impact of each factor depends on the particular process. Moreover, several studies discuss a pore size dependency of precipitation.…”

Probabilistic nucleation governs time, amount, and location of mineral precipitation and geometry evolution in the porous medium

“…Alterations in porosity and connectivity lead to pore space morphology changes, affecting properties such as tortuosity and permeability of the altered medium, and therefore, changes in fluid flow and solute transport 6 – 8 . Mineral precipitation may partially or entirely clog pores and throats in the porous medium and change pore size distribution 4 , 9 , 10 . Even small amounts of solid accumulation may render the pore structure impermeable 3 .…”

“…Even small amounts of solid accumulation may render the pore structure impermeable 3 . Additionally, precipitation reshapes the available surface area for growth, leading to changes in the system’s reactivity, reaction progress, and reaction rates 6 , 10 .…”