scholarly journals Study on the Fractal Characteristics of Coal Body Fissure Development and the Law of Coalbed Methane Migration of around the Stope

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
He Yang ◽  
Zhen Liu ◽  
Danliang Zhu ◽  
Wenzhi Yang ◽  
Dawei Zhao ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Coal Seam ◽  
Coalbed Methane ◽  
Fractal Theory ◽  
Return Flow ◽  
Extraction Technology ◽  
Extraction Field ◽  
Gas Desorption ◽  
Fracture Development ◽  
The Relationship

Due to the complicated coalbed methane (CBM) occurrence conditions and the diverse geological structures in China, the promotion and application of the coal and gas simultaneous extraction technology have been seriously restricted. In view of this, this paper chooses Qingdong Coal Mine protection layer mining and CBM extraction field practice as the research background. Firstly, based on the similar material simulation experiment that simulates coal mining, the dynamic changing pattern of a mining field’s overburdened strata and corresponding stress are obtained, the relationship between gas desorption and stress can then be clarified. Further, with the help of the fractal theory and box counting method, the fracture development characteristics of the overlying strata are quantitatively described on the basis of experimental images. Finally, by building a model for calculating the penetrability coefficient of coal seam based on fractal dimension of mining fissure and analyzing the relationship between fissure development and fractal dimension, the gas migration law and the fissure development areas of #7 and #8 overburden strata where CBM concentrates can be revealed and determined. According to the orientation of the area mentioned above, the location of the CBM pumping field in relation to the coal seam roof and the arrangement of CBM extraction boreholes can be optimized, which make CBM extraction efficient. Meanwhile, the risk of coal and gas outburst is significantly reduced when the CBM concentration is controlled within 0.2% to 0.6% outside the corner of the working face and 0.1% to 0.35% in return flow, which is lower than 0.8%, the threshold of CBM concentration.

scholarly journals Quantify Coal Macrolithotypes of a Whole Coal Seam: A Method Combing Multiple Geophysical Logging and Principal Component Analysis

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 213
Author(s):  
Chao Cui ◽  
Suoliang Chang ◽  
Yanbin Yao ◽  
Lutong Cao
Keyword(s):  
Principal Component Analysis ◽  
Coal Seam ◽  
Coalbed Methane ◽  
Principal Component ◽  
Component Analysis ◽  
Gas Production ◽  
Index Model ◽  
Geophysical Logging ◽  
The Relationship ◽  
Observation Results

Coal macrolithotypes control the reservoir heterogeneity, which plays a significant role in the exploration and development of coalbed methane. Traditional methods for coal macrolithotype evaluation often rely on core observation, but these techniques are non-economical and insufficient. The geophysical logging data are easily available for coalbed methane exploration; thus, it is necessary to find a relationship between core observation results and wireline logging data, and then to provide a new method to quantify coal macrolithotypes of a whole coal seam. In this study, we propose a L-Index model by combing the multiple geophysical logging data with principal component analysis, and we use the L-Index model to quantitatively evaluate the vertical and regional distributions of the macrolithotypes of No. 3 coal seam in Zhengzhuang field, southern Qinshui basin. Moreover, we also proposed a S-Index model to quantitatively evaluate the general brightness of a whole coal seam: the increase of the S-Index from 1 to 3.7, indicates decreasing brightness, i.e., from bright coal to dull coal. Finally, we discussed the relationship between S-Index and the hydro-fracturing effect. It was found that the coal seam with low S-Index values can easily form long extending fractures during hydraulic fracturing. Therefore, the lower S-Index values indicate much more favorable gas production potential in the Zhengzhuang field. This study provides a new methodology to evaluate coal macrolithotypes by using geophysical logging data.

STUDY ON EVOLUTION OF FRACTAL DIMENSION FOR FRACTURED COAL SEAM UNDER MULTI-FIELD COUPLING

Fractals ◽  
2020 ◽  
Vol 28 (04) ◽  
pp. 2050072 ◽  
Author(s):  
GUANNAN LIU ◽  
BOMING YU ◽  
DAYU YE ◽  
FENG GAO ◽  
JISHAN LIU
Keyword(s):  
Fractal Dimension ◽  
Coal Seam ◽  
Pore Structure ◽  
Fractal Theory ◽  
In Situ Stress ◽  
Volume Strain ◽  
Fracture Length ◽  
Field Coupling ◽  
Pore Evolution ◽  
Fractured Coal

In the process of gas extraction, fracture-pore structure significantly influences the macroscopic permeability of coal seam. However, under the multi-field coupling, the mechanism of coal seam fracture-pore evolution remains to be clarified. In this paper, considering the effect of adsorption expansion, the fractal theory for porous media coupled with the multi-field model for coal seam is considered, and a multi-field coupling mechanical model is constructed by considering the influence of fracture-pore structure. Furthermore, the evolution mechanism of fractal dimension with physical and mechanical parameters of coal seam is studied. It is found that the fractal dimension for coal seam is inversely proportional to mining time and in situ stress, proportional to elastic modulus, Langmuir volume constant and Langmuir volume strain constant, and inversely proportional to Langmuir pressure constant. Compared with other factors, Langmuir pressure constant and Langmuir volume strain constant have the significance influence on the fractal dimension for the fracture length.

EFFECT OF FRACTAL FRACTURES ON PERMEABILITY IN THREE-DIMENSIONAL DIGITAL ROCKS

Fractals ◽  
2019 ◽  
Vol 27 (01) ◽  
pp. 1940015 ◽  
Author(s):  
WEIFENG LV ◽  
GUOLIANG YAN ◽  
YONGDONG LIU ◽  
XUEFENG LIU ◽  
DONGXING DU ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Fractal Theory ◽  
Fractured Reservoirs ◽  
Three Dimensional ◽  
Absolute Permeability ◽  
Fracture Aperture ◽  
Fracture Networks ◽  
Discrete Fracture Networks ◽  
Discrete Fracture ◽  
The Relationship

The fracture has great impact on the flow behavior in fractured reservoirs. Fracture traces are usually self-similar and scale-independent, which makes the fractal theory become a powerful tool to characterize fracture. To obtain three-dimensional (3D) digital rocks reflecting the properties of fractured reservoirs, we first generate discrete fracture networks by stochastic modeling based on the fractal theory. These fracture networks are then added to the existing digital rocks of rock matrixes. We combine two low-permeable cores as rock matrixes with a group of discrete fracture networks with fractal characteristics. Various types of fractured digital rocks are obtained by adjusting different fracture parameters. Pore network models are extracted from the 3D fractured digital rock. Then the permeability is predicted by Darcy law to investigate the impacts of fracture properties to the absolute permeability. The permeability of fractured rock is subject to exponential increases with fracture aperture. The relationship between the permeability and the fractal dimension of fracture centers is exponential, as well as the relationship between permeability and the fractal dimension of fracture lengths.

scholarly journals Review about the Application of Fractal Theory in the Research of Packaging Materials

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 860
Author(s):  
Qingshan Duan ◽  
Jiejie An ◽  
Hanling Mao ◽  
Dongwu Liang ◽  
Hao Li ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Fractal Analysis ◽  
Fractal Theory ◽  
Inorganic Materials ◽  
Packaging Materials ◽  
Analysis Method ◽  
Characteristic Parameters ◽  
Fractal Characteristic ◽  
Fractal Characteristics ◽  
The Relationship

The work is intended to summarize the recent progress in the work of fractal theory in packaging material to provide important insights into applied research on fractal in packaging materials. The fractal analysis methods employed for inorganic materials such as metal alloys and ceramics, polymers, and their composites are reviewed from the aspects of fractal feature extraction and fractal dimension calculation methods. Through the fractal dimension of packaging materials and the fractal in their preparation process, the relationship between the fractal characteristic parameters and the properties of packaging materials is discussed. The fractal analysis method can qualitatively and quantitatively characterize the fractal characteristics, microstructure, and properties of a large number of various types of packaging materials. The method of using fractal theory to probe the preparation and properties of packaging materials is universal; the relationship between the properties of packaging materials and fractal dimension will be a critical trend of fractal theory in the research on properties of packaging materials.

Study about Characteristics of Cement Paste on Fractal Theory

2013 ◽  
Vol 423-426 ◽  
pp. 1051-1054
Author(s):  
Tian Yang Zhai
Keyword(s):  
Compressive Strength ◽  
Fractal Dimension ◽  
Cement Paste ◽  
Permeability Coefficient ◽  
Fractal Theory ◽  
Fractal Model ◽  
Concrete Compressive Strength ◽  
Internal Pore Structure ◽  
The Relationship ◽  
Internal Pore

A fractal model to simulate cement paste internal pore structure, and on this basis deduce that fractal dimension is D and the corresponding pore is r, the relationship between porosity is P. MIP was measured test. Then calculated the different ages of the fractal dimension of cement and concrete compressive strength, tensile strength and permeability coefficient. The results showed that: compressive strength, permeability and fractal dimension has a good correlation. Whey in cement in the process of hydration of cement products continue to fill the pores, making the compressive strength increased 70%, permeability is declining.

Particles Gradation Optimization of Blasting Rockfill Based on Fractal Theory

2011 ◽  
Vol 366 ◽  
pp. 469-473 ◽  
Author(s):  
Sheng Zhu ◽  
Yan Ming Feng ◽  
Shu Rong Feng ◽  
Wu Yi Chen
Keyword(s):  
Fractal Dimension ◽  
Test Data ◽  
Fractal Theory ◽  
Average Diameter ◽  
Optimization Method ◽  
Dry Density ◽  
Rock Blasting ◽  
Rockfill Dam ◽  
Under Construction ◽  
The Relationship

Based on fractal theory, used the index of rockfill compaction characteristics(granularity fractal dimension) which conforms to Talbot curve distribution, combined with blasting schemes and rolling test data of several domestic rockfill dams, the relationship is established between compacted rockfill’s dry density and rock blasting parameters by rockfill granularity fractal dimension and its average diameter, and that provided the basis for rockfill particle grading optimization method. The method is applied by rockfill of JIANGPINGHE dam under construction, and the results show that this method can well reflect the intrinsic relation between rock blasting and rockfill compaction, which can be applied to particle grading design of rockfill dam.

Quantitative Identification of Reservoir Fracture with the Variable Scale Fractal Technique in Su53 Gas Field, Ordos Basin

2014 ◽  
Vol 1010-1012 ◽  
pp. 1723-1726
Author(s):  
Hua Wen
Keyword(s):  
Fractal Dimension ◽  
Ordos Basin ◽  
Horizontal Wells ◽  
Gas Field ◽  
Gas Well ◽  
Response Characteristics ◽  
Vertical Heterogeneity ◽  
Fracture Development ◽  
Single Well ◽  
The Relationship

Typical tight gas reservoirs in the Su53 Gas Field, Ordos Basin, are the demonstration region for deploying horizontal wells. In order to provide foundation for evaluating the volume fracturing adaptability of horizontal wells, through using the amplitude difference data between deep investigate double lateral resistivity (Rd) and shallow investigate double lateral resistivity (Rs), and other conventional logging data, in combination with the response characteristics of fracture in the logging curve, reservoir fracture was quantitatively identified with the variable scale fractal technique, the vertical heterogeneity of fracture distribution was analyzed, and the relationship between fractal dimension value of fracture and initial deliverability of gas well was researched. The results indicate that, this method is applied to quantitatively identify and evaluate the fracture development degree of single-well is feasible; the relationship between fractal dimension value and fracture development degree is positively relative, fractal dimension value is bigger, the fracture is more developed; there is a good corresponding relationship between fractal dimension value and deliverability of gas well, fractal dimension value decreases with a decrease of deliverability.

scholarly journals A study on the effects of the fractal characteristics of aggregates on the mechanical behavior of cemented sand and gravel

2021 ◽  
Vol 71 (342) ◽  
pp. e250
Author(s):  
L. Guo ◽  
S. Li ◽  
L. Zhong ◽  
L. Guo ◽  
L. Wang ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Elastic Modulus ◽  
Fractal Theory ◽  
Peak Stress ◽  
Aggregate Gradation ◽  
Cemented Sand ◽  
Ordinary Concrete ◽  
Fractal Characteristics ◽  
Sand And Gravel ◽  
The Relationship

Owing to complex aspects of cemented sand and gravel (CSG), such as included unscreened aggregates, CSG properties differ from those of ordinary concrete. Fractal theory is introduced to study the effects of aggregate characteristics on CSG properties, quantifying aggregate gradation and shape. Numerical simulation and analyses show that: (1) improved aggregate gradation decreases the gradation fractal dimension and increases the CSG peak stress and elastic modulus; (2) more irregularly shaped aggregates increase the shape fractal dimension and decrease the CSG peak stress and elastic modulus; (3) the relationship quantified between aggregate characteristics and CSG mechanical properties provides a theoretical basis for aggregate allocation in engineering design and construction. Mixing artificial aggregates can improve aggregate gradation but reduces CSG performance. Appropriately blending artificial and on-site aggregates achieves optimal CSG performance; in this study, this is attained using 20% artificial aggregates added under standard gradation.

A STUDY ON GAS DRAINAGE CONSIDERING COUPLING PROCESS OF FRACTURE-PORE MICROSTRUCTURE AND COAL DEFORMATION

Fractals ◽  
2021 ◽  
Vol 29 (02) ◽  
pp. 2150065
Author(s):  
LIU GUANNAN ◽  
YE DAYU ◽  
YU BOMING ◽  
GAO FENG ◽  
CHEN PEIJIAN
Keyword(s):  
Fractal Dimension ◽  
Coal Seam ◽  
Fractal Theory ◽  
Coupling Model ◽  
Coal Bed ◽  
Gas Migration ◽  
Gas Drainage ◽  
Field Coupling ◽  
Distribution Rule ◽  
Coal Deformation

Coal seam contains a large number of fractures, whose shape and structure of fissures are complicated, and they are the main channels for gas migration. Therefore, the quantitative analysis of the internal relationship between the microstructure and the macroscopic permeability is the key issue to increase the drainage volume. Some investigators discussed the permeability of coal seams based on the fractal theory, but the mechanisms of gas migration under the influence of fissure microstructures and coal deformation are still unclear. Moreover, most of the multi-process coupling analysis in the stage of Coal Bed Methane (CBM) mining was not taken into account. In this paper, the effects of fissure structures on the coal gas drainage rate in multi-field coupling are studied. Aiming at the mechanisms of gas drainage under the joint action of fracture structure, in-situ stress and adsorption deformation, we propose a two-scale multi-field coupling model, which takes into account the influences of micro fracture and pore structure. On this basis, we obtained the pressure evolution rule of coal seam pore system and fissure system and the distribution rule of coal seam displacement with drilling positions. Meanwhile, the effects of coal seam maximum fracture length, maximum pore diameter, the fractal dimension for fractures and fractal dimension for pores on coal seam extraction are discussed.

Study on the Distribution Law of the Crashed Coal Fragmentation

2011 ◽  
Vol 189-193 ◽  
pp. 1834-1839
Author(s):  
Jia Jia Zhang ◽  
Chang Long Du ◽  
Song Yong Liu ◽  
Hao Jiang
Keyword(s):  
Fractal Dimension ◽  
Weibull Distribution ◽  
Fractal Theory ◽  
Mathematic Model ◽  
Distribution Functions ◽  
Distribution Law ◽  
Characteristic Index ◽  
Fractal Distribution ◽  
The Relationship ◽  
Fragmentation Degree

In order to find the distribution law of coal fragmentation, mathematic model of size distribution was built according to fractal theory. Based on this, the experiments of impactive crash were carried out under different impact rate and different Protodikonov's hardness. The comparison between Weibull distribution and fractal distribution was done so as to find the relationship between the influence parameters and the coal fragmentation characteristic index, the coal fragmentation degree coefficient and the fractal dimension. The results indicate that both two types of distribution functions are suitable for the distribution discipline of coal fragmentation, but the relationship of the coal fragmentation degree and impact parameter is not reacted correctly by the coal fragmentation characteristic index and coal fragmentation degree coefficient in the Weibull distribution while the coal fragmentation degree could be expressed by the fractal dimension in fractal distribution. The relationships between the fractal dimension and the rate, the Protodikonov's hardness of coal are linear.

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