scholarly journals Study on Permeability Characteristics of Rocks with Filling Fractures Under Coupled Stress and Seepage Fields

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2782
Author(s):  
Zhende Zhu ◽  
Zihao Niu ◽  
Xiangcheng Que ◽  
Cheng Liu ◽  
Yanxin He ◽  
...  
Keyword(s):  
Fractured Rock ◽  
Great Influence ◽  
Filling Material ◽  
Rigid Spheres ◽  
Coupling Condition ◽  
Permeability Model ◽  
True Triaxial ◽  
Seepage Pressure ◽  
Permeability Characteristics ◽  
Mineral Particles

Infilling fractured rock masses are widely distributed in the deeply buried oil reservoirs and surrounding rocks of mine caves. The internal filling material has a great influence on the mechanical properties and seepage characteristics of fractured rock mass. In this paper, through theories and experiments, the mechanism of permeability changes of infilling fractured rock under a coupling condition is studied. In terms of theory, the fracture compaction effect coefficient δ is added to the classical matchstick model, and the volume strain principle is used to propose a permeability model for fractured rock. Furthermore, based on the Hertz contact theory, mineral particles are generalized into rigid spheres, and the mechanism of crack development between mineral particles under seepage pressure is analyzed. In terms of experiment, a true triaxial seepage test was carried out on rock-like specimens to obtain the change law of the permeability characteristics of fractured rock. The test results are largely consistent with the theoretical calculation results of the theoretical model, which verifies the applicability of the model proposed in this paper. After the loading failure of the specimen, the internal filling material was taken out and analyzed, and by observing the distribution of cracks on the surface, it is verified that the seepage pressure promotes the development of cracks in the filling fracture.

scholarly journals Experimental Study on Nonlinear Seepage Characteristics and Particle Size Gradation Effect of Fractured Sandstones

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Xuyang Shi ◽  
Wei Zhou ◽  
Qingxiang Cai ◽  
Xiang Lu
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Fractured Rock ◽  
Average Pore Size ◽  
Fractured Rock Mass ◽  
Average Pore ◽  
Seepage Pressure ◽  
Seepage Characteristics ◽  
Fractured Sandstone ◽  
Particle Size Gradation

Seepage mutation of fractured rock mass is one of the main inducements of dump slide and other disasters. Pore structure is a significant factor affecting the seepage characteristics of fractured rock mass, while particle size gradation has an important effect on the distribution of pore structure. Through the self-developed experimental system, the nonlinear seepage test on the fractured sandstones of the coalseam roof was conducted to investigate the influence of seepage pressure, porosity, and fractal dimension. Besides, the nonlinear seepage model was established by Barree–Conway theory. The results showed that, during the seepage process of fractured sandstone, there were significant nonlinear characteristics, which increased with the increase of the seepage pressure. With the increasing porosity, there was greater average pore size of fractured sandstone, stronger permeability, and weaker nonlinear seepage. The seepage characteristics approximated to that of Darcy model. However, with increasing grading fractal dimension, there were smaller average pore size of fractured sandstone, weaker permeability, and stronger nonlinear seepage. The seepage characteristics approximated to that of Forchheimer model.

Connectivity Evaluation of Water Curtain System of Underground Oil Storage Caverns

2014 ◽  
Vol 711 ◽  
pp. 566-570
Author(s):  
Wen Sheng Yu ◽  
Yang Ping
Keyword(s):  
Fractured Rock ◽  
Underground Water ◽  
Fractured Rock Mass ◽  
Permeability Characteristics ◽  
Engineering Research ◽  
Water Curtain ◽  
Oil Storage ◽  
Seal Oil ◽  
Water Seal ◽  
Artificial Water

The connectivity of water curtain between holes must be known to ensure water seal effect of artificial water curtain system of the underground oil storage caverns. The permeability characteristics of the fractured rock mass is analysed based on packer test and validity test of the water curtain holes of the China's HuangDao’s national petroleum reserve underground water seal oil engineering, puts forward the connectivity judgment criterion of water curtain holes, and evaluate the connectivity of water curtain system of underground oil storage caverns. This criterion has been used in the connectivity evaluation of water curtain system of the HuangDao’s national petroleum reserve underground water seal oil engineering. Research provides a basis for the dynamic design of water curtain system of underground oil storage caverns, reduce project cost.

Elasto-Plastic Cellular Automaton Simulation of Fracturing Process in Single Pre-Fractured Rocks under Uniaxial Compression

2010 ◽  
Vol 34-35 ◽  
pp. 383-386 ◽  
Author(s):  
Hua Yan Yao ◽  
Peng Zhi Pan
Keyword(s):  
Cellular Automaton ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Fractured Rock ◽  
Failure Process ◽  
Great Influence ◽  
Rock Fracturing ◽  
Rock Heterogeneity ◽  
Fracturing Process ◽  
Rock Specimens

Rock is a natural heterogeneous material and presents complicated behaviors in the fracturing process. It is prevail to study the basic failure mechanism of rocks via numerical simulation. Based on the elasto-plastic cellular automaton (EPCA) model, this paper simulates single pre-fractured rock fracturing process with consideration of rock heterogeneity on the meso-scale. In this model, the Weibull’s distribution, which characterizes heterogeneity with the homogeneous index m and the random seed parameter s, is adopted to describe the distribution of mechanical parameters of rock specimens such as cohesive strength, Young’s modulus, etc. Pre-existing crack rock specimens with different homogeneous index or the different random seed are simulated by EPCA under uniaxial compression. Numerical results show that heterogeneity has great influence on pre-fractured rock failure process, final failure modes, and the uniaxial compressive strength.

scholarly journals Experimental Study on Seepage Characteristics of Fractured Rock Mass under Different Stress Conditions

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ma Haifeng ◽  
Yao Fanfan ◽  
Niu Xin’gang ◽  
Guo Jia ◽  
Li Yingming ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Permeability Coefficient ◽  
Fractured Rock ◽  
Axial Strain ◽  
Strain Curve ◽  
Confining Pressure ◽  
Strain Effect ◽  
Permeability Evolution ◽  
Hoop Strain ◽  
Permeability Characteristics

In order to obtain the mechanical behavior and permeability characteristics of coal under the coupling action of stress and seepage, permeability tests under different confining pressures in the process of deformation and destruction of briquette coal were carried out using the electrohydraulic servo system of rock mechanics. The stress-strain and permeability evolution curves of briquette coal during the whole deformation process were obtained. The mechanical behavior and permeability coefficient evolution response characteristics of briquette coal under stress-seepage coupling are well reflected. Research shows that stress-axial strain curve and the stress-circumferential strain curve have the same change trend, the hoop strain and axial strain effect on the permeability variation law of basic consistent, and the permeability coefficient with the increase of confining pressure and decreases, and the higher the confining pressure, the lower the permeability coefficient, the confining pressure increases rate under the same conditions, and the permeability coefficient corresponding to high confining pressure is far less than that corresponding to low confining pressure. The confining pressure influences the permeability of the briquette by affecting its dilatancy behavior. With the increase of the confining pressure, the permeability of the sample decreases, and the permeability coefficient decreases with the increase of the confining pressure at the initial stage, showing a logarithmic function. After failure, briquette samples show a power function change rule, and the greater the confining pressure is, the more obvious the permeability coefficient decreases.

Shale permeability model considering bedding effect under true triaxial stress conditions

2019 ◽  
Vol 68 ◽  
pp. 102908 ◽  
Author(s):  
Chao Liu ◽  
Guangzhi Yin ◽  
Minghui Li ◽  
Bozhi Deng ◽  
Zhenlong Song ◽  
...  
Keyword(s):  
Stress Conditions ◽  
Triaxial Stress ◽  
Permeability Model ◽  
True Triaxial ◽  
True Triaxial Stress ◽  
Shale Permeability

scholarly journals A Novel Porous Media Permeability Model Based on Fractal Theory and Ideal Particle Pore-Space Geometry Assumption

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 510 ◽  
Author(s):  
Yongquan Hu ◽  
Qiang Wang ◽  
Jinzhou Zhao ◽  
Shouchang Xie ◽  
Hong Jiang
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Fractal Theory ◽  
Great Influence ◽  
Particle Radius ◽  
Particle Model ◽  
Permeability Model ◽  
Minimum Value ◽  
Pore Area ◽  
The Impact

In this paper, a novel porous media permeability model is established by using particle model, capillary bundle model and fractal theory. The three-dimensional irregular spatial characteristics composed of two ideal particles are considered in the model. Compared with previous models, the results of our model are closer to the experimental data. The results show that the tortuosity fractal dimension is negatively correlated with porosity, while the pore area fractal dimension is positively correlated with porosity; The permeability is negatively correlated with the tortuosity fractal dimension and positively correlated with the integral fractal dimension of pore surface and particle radius. When the tortuosity fractal dimension is close to 1 and the pore area fractal dimension is close to 2, the faster the permeability changes, the greater the impact. Different particle arrangement has great influence on porous media permeability. When the porosity is close to 0 and close to 1, the greater the difference coefficient is, the more the permeability of different arrangement is affected. In addition, the larger the particle radius is, the greater the permeability difference coefficient will be, and the greater the permeability difference will be for different particle arrangements. With the increase of fractal dimension, the permeability difference coefficient first decreases and then increases. When the pore area fractal dimension approaches 2, the permeability difference coefficient changes faster and reaches the minimum value, and when the tortuosity fractal dimension approaches 1, the permeability difference coefficient changes faster and reaches the minimum value. Our research is helpful to further understand the connotation of medium transmission in porous media.

scholarly journals Analysis on rock fracture signals and exploration of infrared advance prediction under true triaxial loading

2021 ◽  
Author(s):  
jiawang hao ◽  
lan qiao ◽  
zhanjin li ◽  
Qingwen Li
Keyword(s):  
Strain Energy ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Prediction Method ◽  
Triaxial Tests ◽  
Sudden Increase ◽  
True Triaxial ◽  
High Temperature Area ◽  
Infrared Monitoring ◽  
Temperature Area

To predict the fractured rock failure under deep triaxial stress in advance, the true triaxial tests were carried out using thermal infrared monitoring and acoustic emission (AE). This paper proposes “infrared temperature jumping rate (ITJR)” to reflect the “jumpiness” of the temperature field matrix, and establishes an infrared advance prediction method. The results show that the high temperature area will converge and expand gradually, and cracks propagate along a certain direction. In the sudden temperature reduction area, the rock stripping is easy to occur. At the boundary between high-low temperature areas, it is easy to produce breakage cracks and form rock spalling. In the short quiet period, the rock gradually gathers strain energy, which will be released in the fracture period. By comparing the time of AE sudden increase with the time of ITJR mutation, it shows that the method has a good advance prediction effect for rock fracture.

Hydraulic fracturing in an unconventional naturally fractured reservoir: a numerical and experimental study

2011 ◽  
Vol 51 (1) ◽  
pp. 507 ◽  
Author(s):  
Mohammad Sarmadivaleh ◽  
Vamegh Rasouli ◽  
Noufal Kakode Shihab
Keyword(s):  
Hydraulic Fracturing ◽  
Numerical Models ◽  
Interaction Mechanism ◽  
Triaxial Stress ◽  
Natural Fracture ◽  
Particle Flow Code ◽  
Filling Material ◽  
Fractured Reservoir ◽  
Natural Fractures ◽  
True Triaxial

Natural fractures play a vital role in the production of low permeability reservoirs when no stimulation techniques are used. The characteristics of natural fractures, together with their pattern that defines how they communicate with each other and to the wellbore, will govern how effectively they can contribute in production enhancement. In most occasions, however, hydraulic fracturing must be used as a remedy to have an economical production rate. Fraccing itself is a complicated process, but would be further complicated when it is practiced in a discontinuous medium. Depending on the properties of the natural fracture(s) and operational condition of the fraccing job, opening, offsetting, crossing or arresting are possible interactions that may happen when an induced fracture reaches a natural discontinuity. In this study, the simplest interaction case with an angle of approach of 90° was studied through both laboratory experiments and numerical modelling. The experiments were carried out under real-triaxial stress conditions using a true-triaxial stress cell (TTSC). Two cement blocks of 20 cm with artificially-made natural fractures were used in this study. The cuts in one sample were filled with weak glue, whereas stiff cement was used in the second sample. The results indicate the importance of interface filling material properties in dominating the interaction mechanism. The numerical models built to simulate these two lab scenarios used particle flow code 2D (PFC2D). The model was tuned and validated against the experimental observations and a good agreement observed between the results of the two approaches.

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