Effect of CO₂ Phase States and Flow Rate on Salt Precipitation in Shale Caprocks—A Microfluidic Study

Abstract

Fracture networks inside the caprock for CO storage reservoirs may serve as leakage pathways. Fluid flow through fractured caprocks and bypass conduits, however, can be restrained or diminished by mineral precipitations. This study investigates precipitation of salt crystals in an artificial fracture network as a function of pressure-temperature conditions and CO phase states. The impact of CO flow rate on salt precipitation was also studied. The primary research objective was to examine whether salt precipitation can block potential CO leakage pathways. In this study, we developed a novel microfluidic high-pressure high-temperature vessel to house geomaterial micromodels. A fracture network was laser-scribed on the organic-rich shales of the Draupne Formation, the primary caprock for the Smeaheia CO storage in Norway. Experimental observations demonstrated that CO phase states influence the magnitude, distribution, and precipitation patterns of salt accumulations. The CO phase states also affect the relationship between injection rate and extent of precipitated salts due to differences in solubility of water in CO and density of different CO phases. Injection of gaseous CO resulted in higher salt precipitation compared to liquid and supercritical CO. It is shown that micrometer-sized halite crystals have the potential to partially or entirely clog fracture apertures.

Experimental mechanical compaction of reconstituted shale and mudstone aggregates: Investigation of petrophysical and acoustic properties of SW Barents Sea cap rock sequences

“…For decades, lab-on-chip experiments and micromodels have provided researchers in various research areas the opportunity to observe fluid flow and solute transport within the pore space (Karadimitriou and Hassanizadeh, 2012). However, majority of the microfluidic studies use engineered material, simple geometries, and ambient pressure-temperature conditions, which makes relevance and applicability of their results limited in the context of deep subsurface conditions in CCS and petroleum sectors (Porter et al, 2015;Nooraiepour et al, 2018b). In CCS, particularly, CO 2 is injected underground in supercritical state, which implies elevated pressure and temperature conditions.…”

“…We are making use of the HPHT microfluidic pressure vessel for a variety of research purposes. The first publication using the developed experimental setup and laboratory technique for sample preparation was on the physics of salt precipitation (Nooraiepour et al, 2018b). The second manuscript is in the final stage of preparation on the effect of mineral heterogeneity on geometry evolution and mineral dissolution in fractured carbonate-rich caprocks.…”

Micro- and Macroscale Consequences of Interactions between CO2 and Shale Rocks

“…More specifically, fractures serving as flow conduits may be clogged by the precipitating salts. Nooraiepour et al [97] studied how fractures in Draupne shale (primary caprocks for Smeaheia CO 2…”

“…Miri et al [92,93] demonstrated the importance of capillary forces on salt precipitation. It has been suggested that drying-induced salt precipitation may have fracture sealing potential [97]. However, it remains unknown whether salt precipitation has any effect on the mechanical properties of shale rocks close to fractures and to to what extent it influences fracture propagation.…”

Contribution of Pore-Scale Approach to Macroscale Geofluids Modelling in Porous Media

“…(2) Validation with 4D Experiments. Challenges should also be focused on validation of numerical predictions [6] on pore-scale processes using wellcontrolled laboratory experiments [7,8]. It has been extremely difficult to visualize 3D time-series (i.e., 4D) data during laboratory experiments that investigate reactive transport through a porous and/or fractured medium at sufficient spatial and temporal resolutions, because the processes of interest occur (deep) inside the medium of interest.…”