Fluid-Driven Instabilities in Granular Media: From Viscous Fingering and Dissolution Wormholes to Desiccation Cracks and Ice Lenses

Abstract

Single and multi-phase fluids fill the pore space in sediments; phases may include gases (air, CH4, CO2, H2, and NH3), liquids (aqueous solutions or organic compounds), and even ice and hydrates. Fluids can experience instabilities within the pore space or trigger instabilities in the granular skeleton. Then, we divided fluid-driven instabilities in granular media into two categories. Fluid instabilities at constant fabric take place within the pore space without affecting the granular skeleton; these can result from hysteresis in contact angle and interfacial tension (aggravated in particle-laden flow), fluid compressibility, changes in pore geometry along the flow direction, and contrasting viscosity among immiscible fluids. More intricate fluid instabilities with fabric changes take place when fluids affect the granular skeleton, thus the evolving local effective stress field. We considered several cases: 1) open-mode discontinuities driven by drag forces, i.e., hydraulic fracture; 2) grain-displacive invasion of immiscible fluids, such as desiccation cracks, ice and hydrate lenses, gas and oil-driven openings, and capillary collapse; 3) hydro-chemo-mechanically coupled instabilities triggered by mineral dissolution during the injection of reactive fluids, from wormholes to shear band formation; and 4) instabilities associated with particle transport (backward piping erosion), thermal changes (thermo-hydraulic fractures), and changes in electrical interparticle interaction (osmotic-hydraulic fractures and contractive openings). In all cases, we seek to identify the pore and particle-scale positive feedback mechanisms that amplify initial perturbations and to identify the governing dimensionless ratios that define the stable and unstable domains. A [N/m] Contact line adhesion

Fingering and strain localization in porous media during imbibition processes

“…The idea is not just to consider the porous network as a sequence of rigid obstacles to the fluid flux but also to account, in the framework of continuum poromechanics and therefore adopting a purely macroscopic point of view, for the effect of this heterogeneous flux on the deformation of the solid skeleton and potential strain localization. As mentioned by several authors, see among others Li and Vanapalli 16 and recently Liu and Santamarina, 17 not just drainage but also imbibition processes can cause fabric changes in fine-grained sediments, which could be associated to contractant behavior (capillary collapse), as proven by Bruchon et al, 18 but also to swelling, because of the alteration of the yield surface and consequently of the reversibility domain. 19 To this purpose the present study develops a poromechanical model based on a phase field approach to partial saturation, 20 in order to overcome the above mentioned weakness of the formulation based on Richards' equation, endowed with an elasto-plastic model taking in due account the effect of saturation on the reduction of strength in a similar way as done by Tamagnini 21 and Rotisciani et al 22 In particular the two above mentioned features of a fine-grained soil (a loamy sand), say its capability to contract or swell under hydraulic imbibition, are discussed as a consequence of the initial state of stress and the rate of change of the yield surface due to saturation.…”

“…Accordingly, the van Genuchten or the simpler Leverett form of k(S r ) can be adopted. 36 Comparison of Equations ( 7) and ( 27), and taking in due account the state equations (17), yield the following generalized form of the isotropic Darcy law:…”

Pore-scale phenomena in carbon geological storage (Saline aquifers—Mineralization—Depleted oil reservoirs)

“…The stress field induced by the crystallization pressure in neighboring pores may trigger an opening mode fracture (Anderson, 2017). Similarly, precipitation may form graindisplacive nodules and lenses in sediments when the crystallization pressure exceeds the in situ effective stress (Shin and Santamarina, 2011;Liu and Santamarina, 2022). Note that precipitated carbonates usually occupy a larger volume than the dissolved source minerals (Snaebjörnsdóttir et al, 2018;Snaebjörnsdóttir et al, 2020), therefore volume Recurrent precipitation in the matrix: Liesegang band formation…”