Dissolution and Seepage Coupling Effect on Transport and Mechanical Properties of Glauberite Salt Rock

Abstract

Potential high rates of aqueous dissolution are characteristic of salt rocks, and solute and mass flux through a soluble porous medium are functions of solute concentration gradients and pressure gradients. Due to different dissolution properties for different mineral components in glauberite salt rock, an interaction between mineral dissolution and solvent seepage arises, driven by the hydraulic pressure gradient in the rock. The originally almost impermeable glauberite rock becomes an increasingly permeable porous medium with dissolution, changing the transport and mechanical properties because of the progressive removal of solid sodium sulfate (Na 2 SO 4 ), one of the constitutive components of glauberite salt rock. Glauberite is often found in bedded salt rock deposits, and the mineral glauberite has economic value and has been mined for many years in China. More economic and safe technologies, such as controlled solution mining, are inherently attractive. Thus, investigations into relevant physical and mechanical properties of glauberite in the context of solution mining have value, and to clarify glauberite behaviour, a series of experiments were performed. It is observed through experiments that the permeability of the rock mass during dissolution of glauberite is a function of the dissolution duration and the hydraulic pressure gradient applied to the system. For example, in laboratory tests, after 49, 53 and 70 h of dissolution, the relationships between permeability (k-cm 2 ) and pressure gradient ( p-MPa across the specimen of length 100 mm) of the glauberite specimens were observed to be k = 0.24 for a p of 0.10, k = 0.30 for a p of 0.12, and k = 0.41 for a p of 0.18, with the empirical functional relationship becoming gradually steeper with pressure. Also, the triaxial compression (mechanical) characteristics of glauberite salt rock change substantially after a period of dissolution: the compressive strength under a confining stress of σ 3 = 2.0 MPa changes initially from 46 to 11 MPa after 70 h of dissolution and seepage. Along with strength degradation, the Young's 123 186 W. Liang et al. modulus (stiffness) changed from 4.6 to 0.5 GPa. Evidently, coupled dissolution and seepage rate greatly impact both transport and mechanical properties of the rock as fabric evolves in a time-dependent manner.

Experimental investigation on the seepage property of saturated broken red sandstone of continuous gradation

“…This makes the porosity and permeability of rock vary with time due to the change of their microstructures (Liang et al 2007;Yuan et al 2016). Some scholars (Chen et al 2014a, b;Wang et al 2014) modified the variable mass seepage experimental system for broken rock tests and conducted a series of variable mass seepage experiments on broken mudstone.…”

Problems of Evolving Porous Media and Dissolved Glauberite Micro-scopic Analysis by Micro-Computed Tomography: Evolving Porous Media (1)

“…Henares et al (2014) studied the effect of pore evolution of Triassic strata caused by chemical dissolution and seepage on oil and gas reservoirs. Liang et al (2008) studied the chemical dissolution and seepage characteristics of glauberite salt rock. Hoefner and Fogler (1988) and Zhang et al (2012) studied pore evolution and channel formation during flow and reaction.…”

A Study of Analytical Solution for the Special Dissolution Rate Model of Rock Salt

“…Liang et al [1] developed a coupling theory for the effects of dissolution and seepage and the mass transfer and mechanical properties of rock salt. Fairchild et al [2] completed a field-test study of the dissolution characteristics 2 Advances in Materials Science and Engineering of NaCl, and they found a positive correlation between the dissolution rate and the surface area of exposure.…”