Nanoscale detection of metastable states in porous and granular media

Abstract

Microseismicity in subsurface geologic environments, such as sandstone gas reservoirs, is expected in the presence of liquid or gas injection. Although difficult to predict, the potential for microseismic events is important to field-scale projects, such as geologic storage of CO2 whereby the gas is injected into natural sandstone formations. We conjecture that a primary factor causing microseismicity is the existence of metastable states in granular porous medium and provide experimental evidence for its validity. External perturbation trigger abrupt relaxation events, which, with a certain probability, can grow into macroscopic microseismic events. Here the triggering perturbation is produced by cooling to a cryogenic temperature. As the "sensor" for the abrupt relaxation events we use thin Al films deposited on the sandstone surface. We show that as the temperature is varied, the films' resistance exhibits sharp jumps, which we attribute to mechanical restructuring or microfractures in the fabric of the sandstone. We checked the superconducting characteristics of the Al thin films on the sandstone and found microwave-induced Shapiro steps on the voltage-current diagrams. Such quantized steps provide indicates that the film is made of a network of nanobridges, which makes it ever more sensitive to abrupt relaxation events occurring in the substrate, i.e., in the underlying sandstone.

Supervision and Assistance Based on Mobile Information System in Art Video Teaching

“…e important role of multimedia teaching began to be realized by many schools and teachers, and multimedia teaching was taken as the main research direction of teaching and research, and it was also introduced into the teaching of various disciplines. When talking about the future teaching, it was generally believed that individualization has become one of the directions of teaching development due to the development of technology [13]. Some scholars have also made positive affirmation on the significance and advantages of multimedia teaching and put forward some problems that need attention on the integration of multimedia and art [14].…”

Failure processes of cemented granular materials

“…Experimental studies [17,18] have also used X-rays to measure more details of brittle faulting of rocks. Similarly, a conductivity-based method was recently used to detect microcracks in sandstone under strong temper-ature variations rather than direct mechanical loading [19]. In general, the statistical properties of the microcrack events, for a range of porosities and materials, have been studied experimentally (see e.g.…”

Pore-Scale Dynamics of Liquid CO2–Water Displacement in 2D Axisymmetric Porous Micromodels Under Strong Drainage and Weak Imbibition Conditions: High-Speed μPIV Measurements

“…Each micromodel consisted of a heterogeneous porous region, an inlet, and an outlet, as shown in Figures 1B,C. The micromodels were fabricated from silicon and glass using microfabrication techniques (Chomsurin and Werth, 2003;Kazemifar et al, 2015;Ilin et al, 2020), with the porous matrix formed with irregularly patterned 2D poly-disperse cylinders mimicking a natural porous medium, inspired by a previous study (Zhao et al, 2016). The porous pattern was based on an irregular mesh created using the pdemesh tool in MATLAB.…”