A modified true triaxial apparatus for measuring mechanical properties of sandstone coupled with CO₂‐H₂O biphase fluid

Abstract

Mechanical behaviors of rock under biphase or multiphase fluids conditions are key scientific issues currently in geomechanics and geotectonics. In this work, we conducted a series of triaxial experiments using a semipermeable separator method to form a specific composition pressure; we comparatively investigated the mechanical behaviors of sandstone in the conditions of monophase fluids CO2/N2/H2O and biphase fluid CO2‐H2O; and we analyzed the strength, elasticity modulus and brittleness of sandstones at different porous fluid conditions. The results showed that the selective adsorption of mineral compositions of sandstone on CO2/N2/H2O has obvious effects on mechanical behaviors. The linear elastic modulus of CO2‐H2O coupled sandstone was slightly greater than that of H2O‐bearing sandstone, but significantly less than that of CO2‐ or N2‐bearing sandstone. Compared to H2O, CO2 or N2 containing sandstones are mainly subjected to the brittle failure and exhibit no obvious plastic deformation. Overall, the study analyzed the mechanisms of physicochemical interactions of fluid with sandstone minerals from the micro‐scales, and revealed the mechanical mechanism between fluids and mineral particles, and established a new effective stress model of sandstone under CO2‐H2O biphase condition. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.

A review of geochemical–mechanical impacts in geological carbon storage reservoirs

“…The early decrease in compaction rate was linked to the suppression of pressure solution creep (stress‐driven mass transfer); meanwhile, the increase was linked to an increase in subcritical microcracking. Recent results by Hu et al . confirm the strong influence of the pore fluid chemistry for sandstones.…”

“…The early decrease in compaction rate was linked to the suppression of pressure solution creep (stress-driven mass transfer); meanwhile, the increase was linked to an increase in subcritical microcracking. Recent results by Hu et al 167 confirm the strong influence of the pore fluid chemistry for sandstones. These changes underscore the importance of a thorough characterization of the rock lithology, morphology, and geological CO 2 storage conditions to understand the impact of CO 2 -induced geomechanical alterations on heterogeneous rocks such as sandstone.…”

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

“…We have already used the same cores to study the influence of the intermediate principal stress (σ 2 ) on the permeability evolution during true triaxial compression [41]. Although this paper emphasizes the effect of confining pressure (P c ) on the strain-permeability behavior of mudstone, which can be tested by a conventional triaxial apparatus with a cylindrical specimen, the true triaxial apparatus for rocks [41][42][43][44][45] at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, which can exert three stresses independently, was still employed in this study because the specimen usually failed with a relatively flat fault parallel to σ 2 [42,[46][47][48]; the flow in the σ 2 direction can still be regarded as a one-dimensional flow. In contrast, the fault of the specimen in the CTC is not only very rough but also oblique to the flow direction [40,49] and the fluid flow inside the specimen near or after failure cannot be approximated as a one-dimensional flow; therefore, the cores in this study were also processed into cuboid specimens of 5 cm square by 10 cm long ( Figure 1) and the permeability in the σ 2 direction was monitored during deviatoric loading.…”

Impact of Chemical Environment on Compaction Creep of Quartz Sand and Possible Geomechanical Applications

“…The observed effects may be extended to the compaction creep of sandstones, when subcritical crack growth controls deformation. Previous workers have shown that microcracking is an important mechanism in sandstone deformation high stresses and strains (Heap et al, ; J. Zhang et al, ) and the presence of water leads to a pronounced weakening effect (Baud et al, ; Hu et al, , ). This suggests that, compared to the behavior of quartz sands, sandstones respond similarly to changes in water content and solution pH and presumably to the introduction of additives such as those studied here.…”