scholarly journals Induced microearthquakes predict permeability creation in the brittle crust

Author(s):  
Ziyan Li ◽  
Derek Elsworth ◽  
Chaoyi Wang

Abstract Fracturing controls rates of mass, chemical and energy cycling within the crust. We use observed locations and magnitudes of microearthquakes (MEQs) to illuminate the evolving architecture of fractures reactivated and created in the otherwise opaque subsurface. We quantitatively link seismic moments of laboratory MEQs to the creation of porosity and permeability at field scale. MEQ magnitudes scale to the slipping patch size of remanent fractures reactivated in shear - with scale-invariant roughnesses defining permeability evolution across nine decades of spatial volumes – from centimeter to decameter scale. This physics-inspired seismicity-permeability linkage enables hybrid machine learning (ML) to constrain in-situ permeability evolution at verifiable field-scales (~10 m). The ML model is trained on early injection and MEQ data to predict the dynamic evolution of permeability from MEQ magnitudes and locations, alone. The resulting permeability maps define and quantify flow paths verified against ground truths of permeability.

2016 ◽  
Author(s):  
Jamie I. Farquharson ◽  
Patrick Baud ◽  
Michael J. Heap

Abstract. Active volcanoes are mechanically dynamic environments, and edifice-forming material may often be subjected to significant amounts of stress and strain. It is understood that porous volcanic rock can compact inelastically under a wide range of in situ conditions. In this contribution, we explore the evolution of porosity and permeability – critical properties influencing the style and magnitude of volcanic activity – as a function of inelastic compaction of porous andesite under triaxial conditions. Progressive strain accumulation is associated with progressive porosity loss. The efficiency of compaction was found to be related to the effective confining pressure under which deformation occurred: at higher effective pressure, more porosity was lost for any given amount of strain. Permeability evolution is more complex, with small amounts of stress-induced compaction ( 0.20) where samples may undergo a reduction in permeability by two orders of magnitude relative to their initial values. A physical limit to compaction is discussed, which we suggest is echoed in a limit to the potential for permeability reduction in compacting volcanic rock. Compiled literature data illustrate that at high strain (both in the brittle and ductile regimes), porosity ϕ and permeability k tend to converge towards intermediate values (i.e. 0.10 ≤ ϕ ≤ 0.20; 10–14 ≤ k ≤10–13 m2). These results are discussed in light of their potential ramifications for impacting edifice outgassing – and in turn, eruptive activity – at active volcanoes.


Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Cong Hu ◽  
Franck Agostini ◽  
Yonggang Jia

Porosity and permeability are the two most important characteristics of underground gas storage in sandstone reservoirs. Injection of gas into reservoir rocks will cause rock deformation. The deformation will influence the porosity and permeability properties of the rocks. We investigate the evolution of these two properties of storage sandstone by triaxial compression tests and a uniaxial in situ compression CT test. As the deviatoric stress increases, the sandstone is compressed firstly (porosity reduction) and then dilates (porosity enhancement). With the increase in confining stress, the occurrence of volumetric dilation will be delayed. Trapped porosity of this sandstone at different deviatoric stresses is very small (0.122%-0.115%) which indicates that nearly all pores are connected. During the compression stage, the decrease in permeability is related to compression of pores and microcracks. During the volumetric dilation stage, it is related to increase in tortuosity. This interpretation can be confirmed by observations of in situ compression CT. The permeability evolution estimated by pore network modeling is consistent with macroscopic testing results.


Science ◽  
2019 ◽  
Vol 366 (6464) ◽  
pp. 475-479 ◽  
Author(s):  
Guohua Dong ◽  
Suzhi Li ◽  
Mouteng Yao ◽  
Ziyao Zhou ◽  
Yong-Qiang Zhang ◽  
...  

Ferroelectrics are usually inflexible oxides that undergo brittle deformation. We synthesized freestanding single-crystalline ferroelectric barium titanate (BaTiO3) membranes with a damage-free lifting-off process. Our BaTiO3 membranes can undergo a ~180° folding during an in situ bending test, demonstrating a super-elasticity and ultraflexibility. We found that the origin of the super-elasticity was from the dynamic evolution of ferroelectric nanodomains. High stresses modulate the energy landscape markedly and allow the dipoles to rotate continuously between the a and c nanodomains. A continuous transition zone is formed to accommodate the variant strain and avoid high mismatch stress that usually causes fracture. The phenomenon should be possible in other ferroelectrics systems through domain engineering. The ultraflexible epitaxial ferroelectric membranes could enable many applications such as flexible sensors, memories, and electronic skins.


1994 ◽  
Vol 29 (10) ◽  
pp. 1251-1274 ◽  
Author(s):  
Céser Gómez-Lahoz ◽  
James M. Rodríguez-Maroto ◽  
David J. Wilson∗
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