scholarly journals Hydraulic and Mechanical Relationship of Individual Fracture in Rock under Compression and Shearing: Theoretical Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Zhiqiang Zhou ◽  
Yu Zhao ◽  
Chaolin Wang
Keyword(s):  
Normal Stress ◽  
Fractured Rock ◽  
Fracture Propagation ◽  
Nonlinear Behavior ◽  
Fracture Aperture ◽  
Fracture Permeability ◽  
Energy Principle ◽  
Permeability Model ◽  
Shear Dilation ◽  
Relationship Of

In this paper, a new approach has been developed for predicting the hydraulic and mechanical relationship of individual fractures subjected to normal stress and compression-shear stress. Considering that the closure process of rough fracture subjected to normal stress can be divided into two phases (linear behavior and nonlinear behavior), a relationship between normal stress and fracture aperture is derived through the minimum potential energy principle. Then, a formulation for calculating fracture permeability during shearing and compression processes is developed. Furthermore, a formulation for determining fracture aperture during the crack growth process is obtained, which is further implanted into the permeability model to predict the hydraulic behavior of fractured rock during fracture propagation. This new model not only considers the normal deformation of the fracture but also, and more importantly, integrates the effect of fracture propagation and shear dilation. Theoretical studies demonstrate that fracture permeability increases nonlinearly during fracture propagation. At last, experimental results and analytic results are compared to demonstrate the usefulness of the proposed models, and satisfactory agreements are obtained.

scholarly journals Experimental Investigation of the Permeability Measurement of Radial Flow through a Single Rough Fracture under Shearing Action

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Ran Tan ◽  
Junrui Chai ◽  
Cheng Cao
Keyword(s):  
Grain Size ◽  
Fracture Surface ◽  
Normal Stress ◽  
Flow Direction ◽  
Fractured Rock ◽  
Shear Velocity ◽  
Test Case ◽  
Fracture Permeability ◽  
Rough Fracture ◽  
Flow Through

Water flow is commonly observed in rock fractures, and this flow has considerable significance in many aspects of rock engineering. In this study, seepage-stress coupled tests were performed on fractured rock masses using a computer-controlled direct shear device for rock with seepage control. The flow direction was radial. Eight types of test case were designed, and subgroup tests with varied normal stress, shear velocity, and roughness of fracture surface were conducted. The failure state of the fracture surface after the shear test, changes in shear stress, and fissure width and permeability under the above conditions were analyzed. The results include the following: the grain size of gouge fragments produced in rough fracture decreased with an increase in normal stress during shearing; the grain size of gouge fragments affected the fracture permeability; and the influence of shear velocity on the test results was mainly reflected after the peak strength. Additionally, a new expression describing fluid flow through fracture gouge is proposed.

scholarly journals Baseflow analysis using master recession curves and numerical algorithms in mountain basins: Suratá's river and Oro's river (Santander, Colombia)

DYNA ◽  
2016 ◽  
Vol 83 (196) ◽  
pp. 213-222
Author(s):  
Sully Gomez Isidro ◽  
Viviana Lucía Gómez-Ríos
Keyword(s):  
River Basin ◽  
Fractured Rock ◽  
Numerical Algorithms ◽  
Mathematical Expression ◽  
Groundwater Inflow ◽  
Additional Information ◽  
Recession Curves ◽  
Master Recession Curve ◽  
Mountain Basins ◽  
Relationship Of

<p>The interaction between groundwater inflow and outflow is complex in streams connected from aquifers located in fractured rock media. The recession curves of hydrographs provide information about these hydrogeological processes and they are useful to assess an insight in the storage-discharge relationship in subsurface reservoirs. In this study, the physic base and the nonlinearity relationship of storagedischarge were analyzed through a mathematical expression which describe a master recession curve. Four numerical algorithms were applied to estimate the baseflow of the Suratá's River basin and the high Oro's River basin, Santander-Colombia. In both cases, master recession curves showed the nonlinearity relationship in storage-discharge. Furthermore, the exponent values and the proportionality constants give additional information about the aquifers in contact to the river and the special scale of recharges that may occur in these aquifers.</p>

A FRACTAL PERMEABILITY MODEL FOR POROUS–FRACTURE MEDIA WITH THE TRANSFER OF FLUIDS FROM POROUS MATRIX TO FRACTURE

Fractals ◽  
2019 ◽  
Vol 27 (06) ◽  
pp. 1950121 ◽  
Author(s):  
TONGJUN MIAO ◽  
AIMIN CHEN ◽  
YAN XU ◽  
SUJUN CHENG ◽  
BOMING YU
Keyword(s):  
Fractal Dimension ◽  
Geothermal Energy ◽  
Theoretical Foundation ◽  
Flow Behavior ◽  
Porous Matrix ◽  
Fracture Aperture ◽  
Permeability Model ◽  
Microstructural Parameters ◽  
Dimension Formula ◽  
Proposed Model

The transfer of fluids from porous matrix to fracture is a key issue to accurately predict the fluid flow behavior in porous–fracture media. In this work, to take into account the transfer of fluids, the analytical model of dimensionless permeability is proposed based on the fractal geometry theory for porous media. The proposed model is expressed as a function of microstructural parameters of the porous matrix and fracture, such as the pore area fractal dimension [Formula: see text], fractal dimension [Formula: see text] for tortuosity of tortuous capillaries, the ratio [Formula: see text] of the maximum pore size in porous matrix to fracture aperture, as well as the ratio [Formula: see text] of the pressure difference along the fracture to that along the porous matrix layers. The model reveals that the ratios [Formula: see text] and [Formula: see text] have significant influences on the permeability contribution from the porous matrix to the seepage behavior of the fracture. While the contribution of porosity of leak-wall porous surface of the fracture to the permeability is less than 10%. The present results may provide an important theoretical foundation for exploration of petroleum, gas and geothermal energy extraction systems.

A new fracture permeability model: Influence of surrounding rocks and matrix pressure

2020 ◽  
Vol 193 ◽  
pp. 107320 ◽  
Author(s):  
Peng Yu ◽  
Yuetian Liu ◽  
Jun Wang ◽  
Chuixian Kong ◽  
Wenhuan Gu ◽  
...  
Keyword(s):  
Fracture Permeability ◽  
Permeability Model

Impact of Various Parameters on the Production of Coalbed Methane

SPE Journal ◽  
2013 ◽  
Vol 18 (05) ◽  
pp. 910-923 ◽  
Author(s):  
Zhongwei Chen ◽  
Jishan Liu ◽  
Akim Kabir ◽  
Jianguo Wang ◽  
Zhejun Pan
Keyword(s):  
Time Constant ◽  
Coalbed Methane ◽  
Dominant Role ◽  
Gas Production ◽  
Fracture Permeability ◽  
Permeability Model ◽  
Gas Desorption ◽  
Desorption Time ◽  
Matrix Blocks ◽  
Cbm Production

Summary Coalbed-methane (CBM) reservoirs are naturally fractured formations, comprising both permeable fractures and matrix blocks. The interaction between fractures and matrix presents a great challenge for the forecast of CBM reservoir performance. In this work, a dual-permeability model was applied to study the parameter sensitivity on the CBM production, because the dual-permeability model incorporates not only the influence from matrix and fractures but also that between adjacent matrix blocks. The mass exchange between two systems is defined as a function of desorption time constant at the standard condition, coal matrix porosity, and the difference of gas pressure between two systems. Correspondingly, gas diffusivity in matrix is considered as a variable and represented by a function of shape factor, gas desorption time, and reservoir pressure. These relations are integrated into a fully coupled numerical model of coal geomechanical deformation and gas desorption/gas flow in both systems. This numerical approach demonstrates the important nonlinear effects of the complex interaction between matrix and fractures on CBM production behaviors that cannot be recovered without rigorously incorporating geomechanical influences. This model was then used to investigate the sensitivity of CBM extraction behavior to different controlling factors, including gas desorption time constant, initial fracture permeability, fracture spacing, swelling capacity, desorption capacity, production pressure, and fracture and matrix porosities. Modeling results show that the peak magnitudes of gas-production rate increase with initial fracture permeability, sorption and swelling capacities, and matrix porosity, and decrease with gas desorption time constant and production pressure. These results also show dramatic increase in gas-production efficiency with decreasing magnitudes of fracture spacing. The comparison of the transient contributions of the desorbed gas and the free phase gas from the matrix system to gas production shows that the free phase gas plays the dominant role at the early stage, but diminishes when the adsorption phase gas takes over the dominant role, indicating the necessity of incorporating free phase gas impact in simulation models. The numerical model was also applied to match the history data from a gas-production well. A better matching result than that for the single-permeability model demonstrates the potential capability of the dual-permeability model for the forecast of CBM production.

Electrical conductivity of brine‐saturated fractured rock

Geophysics ◽  
1986 ◽  
Vol 51 (8) ◽  
pp. 1585-1593 ◽  
Author(s):  
R. M. Stesky
Keyword(s):  
Electrical Conductivity ◽  
Fracture Surface ◽  
Contact Area ◽  
Fractured Rock ◽  
Flow Path ◽  
Fracture Plane ◽  
Fracture Aperture ◽  
Height Distribution ◽  
Surface Geometry ◽  
Path Tortuosity

A theoretical analysis shows that electrical conductivity along fractures in a saturated porous rock is a function of many factors: fluid and rock conductivities, initial fracture aperture and contact area, fracture surface geometry (asperity height distribution and tip curvature), elastic moduli of the rock, and confining pressure or normal stress acting across the fracture. The conductivity in the fracture plane decreases approximately in proportion to log pressure, but the conductivity is influenced by the increased contact area, and hence flow‐path tortuosity, along the fracture surface at elevated pressures. Electrical conductivity in fractures is more affected by flow‐path tortuosity than is permeability. The dependence on pressure was tested using laboratory measurements of conductivity through split cores containing ground, saw‐cut surfaces in a variety of rocks under confining pressures to 200 MPa. The conductivity decreased approximately in proportion to log pressure (there was little effect of increased contact area, and hence tortuosity), which suggests that the contact area may not exceed a few percent of the total apparent area. Measurements of gas permeability through the same split cores showed that when the asperity deformation remained largely elastic, permeability and conductivity had a power of 3 relationship. When asperity collapse occurred, as in a dolomitic marble, the powerlaw relation no longer held; permeability decreased more rapidly under pressure than did conductivity. The different influences of porosity and flow aperture may account for the different behaviors of the two transport properties. The theory suggests a number of ways in which fracture parameters may be extracted from field data. Some of the methods rely on the scale dependence and pressure dependence of the fractured‐rock conductivity; other methods require correlating between different physical properties, such as seismic velocity, which are influenced by the presence of fractures.

scholarly journals Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Xue-wei Liu ◽  
Quan-sheng Liu ◽  
Shi-bing Huang ◽  
Lai Wei ◽  
Guang-feng Lei
Keyword(s):  
Fractured Rock ◽  
Fracture Propagation ◽  
Propagation Characteristic ◽  
Propagation Path ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Microdamage Accumulation ◽  
Macroscopic Fracture ◽  
Crack Tips ◽  
Ae Location

This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C). On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the propagation paths are affected by the loading condition obviously. Then, by adopting acoustic emission (AE) location technique, AE event localization characteristics in the process of loading are investigated. The locations of AE events are in good agreement with the macroscopic fracture propagation path. Finally, the micromechanism of macroscopic fracture propagation under uniaxial and biaxial compression conditions is analyzed, and the fracture propagation can be concluded as a result of microdamage accumulation inside the material. The results of this paper are helpful for theory and engineering design of the fractured rock mass.

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