The permeability properties of bedded coal and rock: Review and new insights

Abstract

It is beneficial to understand deeply the permeability properties of coal and rock for the stability control of mining engineering, underground engineering, oil and gas engineering, nuclear waste storage engineering, and so on. Therefore, new insights for the permeability properties of bedded coal and rock are summarized and proposed. (1) "Five guarantees" coring technology is worth for vigorous promotion and application. (2) The internal spatial fabric has the significant effect on the mechanical behavior evolution law of (bedded) coal and rock, but the effect is not dominant. (3) The permeability‐energy evolution models of (bedded) coal and rock should be constructed considering the idea of initial high in situ stress reduction, which is helpful for the energy visualization characterization of (bedded) coal and rock. Meanwhile, it can be combined with the structural evolution theory for in‐depth characterization and disclosure. (4) Researches on the permeability properties of (bedded) coal and rock under multi‐field or multi‐phase or phase‐field coupling conditions should be strengthened based on considering the initial damage produced and the distribution characteristics of in situ stress under the coring environment. (5) More accurate and scientific permeability evolution models of (bedded) coal and rock should be vigorously constructed based on the above insights.

Evolution law and application of permeability in gob without coal pillar and self‐formed roadway

“…Many scholars regard Darcy's law as the laminar flow law of porous media and use hydrodynamic theory and methods to study the relationship between permeability, porosity, and particle size of porous media bodies 28 . The formula of permeability in the extraction zone can be obtained as follows: $$$e=\frac{{D}_{P}^{2}}{C}\times \frac{{n}^{3}}{{(1-n)}^{2}},$$$where, e is the permeability (m 2 ); n is the porosity of porous media; c is constant; D p is average particle diameter (m), hereby the field observations were taken 0.3 m.…”

“…Many scholars regard Darcy's law as the laminar flow law of porous media and use hydrodynamic theory and methods to study the relationship between permeability, porosity, and particle size of porous media bodies. 28 The formula of permeability in the extraction zone can be obtained as follows:…”

Mohr–Coulomb and Modified Hoek–Brown Strength Criteria of Layered Sandstone Considering the Unloading Effect and Anisotropy

“…Furthermore, there exists the obvious evolution process of the stress state of roadway surrounding rocks before excavation, during excavating and after excavation (see Figure 1b). Therefore, the stress path TLUT considering the unloading effect was proposed [36,37]. Furthermore, it was expected to improve the accuracy of the applicability of the strength criteria.…”

“…Furthermore, it was expected to improve the accuracy of the applicability of the strength criteria. [36,37]. Note: H, σ1 and σ3 represent the buried depth, axial stress and confining pressure, respectively; σx, σy, σz, σx' and σz' represent the minimum principal stress, the intermediate principal stress, the maximum principal stress, the minimum principal stress after unloading and the maximum principal stress after re-loading.…”

Critical drawdown pressure prediction for sanding production of underground gas storage in a depleted reservoir in China

“…As a clean, low-carbon, stable, efficient and economic fossil energy, natural gas plays an important role in heating supply, electricity generation, industry and national energy strategic reserve. [1][2][3][4] Underground gas storage (UGS), as the optimal choice for seasonal peak shaving, emergency gas supply and energy strategic reserve, is characterized by significant advantages of large storage capacity, wide regulation range and low operating costs. [5][6][7] UGS can be classified as: depleted oil and gas reservoir, aquifer, salt cavern, and abandoned pit.…”