Changes in Pore Geometry and Connectivity in the Basalt Pore Network Adjacent to Fractures in Response to CO₂‐Saturated Fluid

Abstract

Basalt formations are often fractured, which poses the risk of CO 2 leakage from a geological CO 2 storage reservoir. Despite their fractured nature, basalts are considered for large-scale CO 2 injection and storage due to large potential storage capacity and rapid carbon mineralization (Matter et al., 2016;McGrail et al., 2016;Xiong et al., 2018). The advantage of fractures is the connectivity to a larger pore network adjacent to fracture surfaces, which provide a large mineral reactive surface area for chemical reactions, and may play a dominant role in changing the porosity of basaltic rock. Mineral precipitation in fractures and connected pores could act as a self-sealing process in the case of a CO 2 leakage from a CO 2 storage reservoir, thus reducing the risk of the longterm leakage of CO 2 . Mineral precipitation in basalt fractures has been observed in natural analogue systems where hydrothermal fluids have migrated upwards through basalts over geological time (Eggleton et al., 1987;Goldberg et al., 2008;Rogers et al., 2006). However, a range of factors including the flow velocity of the CO 2 -enriched plume, fluid chemistry, pressure and temperature conditions, and the fracture aperture size need to be considered in order to predict the rate and extent of the potential self-sealing of fractures (Brunet et al., 2016).Several laboratory studies have been performed to understand the influence of transport limitations on the extent of mineral formation and pore network alterations in natural basalt cores when exposed to acidic CO 2 -rich fluids under relevant geologic storage conditions (

Comparison of Petrophysical Properties of Porous Rocks Using NMR, Micro-CT, and Fluid Flow Simulations

“…This is carried out by computing watershed lines on the binarized image. This method is a high-level combination of the watershed, distance transform, and numerical reconstruction algorithm [58][59][60][61]. The first step is constructing a chamfer distance map, which represents the minimal distance of a voxel from the pore boundary.…”

“…The ideal pore is a sphere with an equivalent volume of the irregular shaped real pore, and the ideal throat is a cylinder with an equivalent surface area as the irregular shaped real throat. The output from this analysis was categorized into known bin ranges and frequency of the pore and throat size distributions were quantified [61]. Pores can be irregular in shape, so the total volume of all the voxels in a pore cluster results in estimating the total volume of the irregular shaped pore clusters.…”

“…The idealized pores are centered according to the actual position of the real pores. The output from the porenetwork model consists of the number of pore and throats in the rock and their equivalent radius [61].…”

A Pore-Scale Phase Field Model for CO2–Fluid–Basalt Interactions

“…Due to the promising potential of basalt for carbon fixation, numerous scholars have extensively investigated the mineral composition and fluid chemical evolution during CO 2 –water–basalt interactions through hydrothermal experiments and/or numerical simulations, revealing the dissolution–precipitation path. − Concurrently, as CO 2 –water–rock interactions induce mineral dissolution and precipitation processes that alter the pore structure of the rock, thereby influencing the subsequent fluid flow behavior, it becomes crucial to elucidate the pore structure evolution during CO 2 geological storage engineering. At present, a large number of experimental observations have revealed the pore structure evolution characteristics of rocks during CO 2 –water–basalt interactions. − However, there are few pore-scale numerical models that describe the evolution of the fluid–solid interface during CO 2 –water–basalt interactions.…”

“…At present, a large number of experimental observations have revealed the pore structure evolution characteristics of rocks during CO 2 –water–basalt interactions. 14 − 18 However, there are few pore-scale numerical models that describe the evolution of the fluid–solid interface during CO 2 –water–basalt interactions.…”