Volatile-consuming reactions fracture rocks and self-accelerate fluid flow in the lithosphere

Abstract

Hydration and carbonation reactions within the Earth cause an increase in solid volume by up to several tens of vol%, which can induce stress and rock fracture. Observations of naturally hydrated and carbonated peridotite suggest that permeability and fluid flow are enhanced by reaction-induced fracturing. However, permeability enhancement during solid-volume–increasing reactions has not been achieved in the laboratory, and the mechanisms of reaction-accelerated fluid flow remain largely unknown. Here, we present experimental evidence of significant permeability enhancement by volume-increasing reactions under confining pressure. The hydromechanical behavior of hydration of sintered periclase [MgO + H2O → Mg(OH)2] depends mainly on the initial pore-fluid connectivity. Permeability increased by three orders of magnitude for low-connectivity samples, whereas it decreased by two orders of magnitude for high-connectivity samples. Permeability enhancement was caused by hierarchical fracturing of the reacting materials, whereas a decrease was associated with homogeneous pore clogging by the reaction products. These behaviors suggest that the fluid flow rate, relative to reaction rate, is the main control on hydromechanical evolution during volume-increasing reactions. We suggest that an extremely high reaction rate and low pore-fluid connectivity lead to local stress perturbations and are essential for reaction-induced fracturing and accelerated fluid flow during hydration/carbonation.

Rift-inversion orogens are potential hotspots for natural H2 generation

“…Other limitations to our models concern the omission of detailed sedimentary history (i.e., timing and availability of reservoirs and seals), as well as detailed natural H2 migration pathways to these reservoirs (e.g., 21; 22). In this context, the impact of density changes during serpentinization also requires attention, since the volumetric expansion of serpentinizing mantle material may either clog water and hydrogen pathways (52) or induce new fracturing and increase permeability (67). Finally, H2 gas is highly reactive and may easily be consumed by (bio)chemical reactions on its way to, or within reservoirs (e.g., 57; 68).…”

A coupled phase-field and reactive-transport framework for fracture propagation in poroelastic media

“…www.nature.com/scientificreports/ chemical weathering (e.g., carbonation and serpentinization) is widely observed in nature [69][70][71] . However, it is a major challenge to reproduce reaction-driven fracture propagation in a lab setting 72,73 . Uno et al 72 studied the hydration of periclase to brucite under confining pressure experimentally in a lab setting.…”

“…However, it is a major challenge to reproduce reaction-driven fracture propagation in a lab setting 72,73 . Uno et al 72 studied the hydration of periclase to brucite under confining pressure experimentally in a lab setting. The volume-increasing hydration reaction resulted in fracture development and enhanced fluid flow.…”

“…The volume-increasing hydration reaction resulted in fracture development and enhanced fluid flow. The experimental setup and data by 72 are a good candidate for future validation and demonstration of our framework. Another example of interest is the potential fracturing during CO 2 mineralization in reactive mafic rock.…”

Decoding the nanoscale porosity in serpentinites from multidimensional electron microscopy and discrete element modelling

“…Recent experiments on a serpentinization-analogue system, involving the hydration of periclase to brucite (MgO + H 2 O → Mg(OH) 2 ), have demonstrated that under conditions of high reaction rates and low pore-fluid connectivity, hydration reactions may increase permeability by approximately three orders of magnitude (Uno et al 2022 ) and reaction-induced stresses could potentially reach gigapascal-levels (Plümper et al 2022 ). These findings differ from previous flow-through serpentinization experiments, which showed a decrease in permeability over several orders of magnitude, mainly caused by the clogging of fluid pathways due to mineral precipitation (Godard et al 2013 ; Farough et al 2016 ).…”