Top PDF Study on the fracture mode of low permeability shale under different confining pressures

Study on the fracture mode of low permeability shale under different confining pressures

Study on the fracture mode of low permeability shale under different confining pressures

Abstract: Rock fracture is a complicated none quilibrium and nonlinear evolution process. There are important theoretical significance and engineering value for the research on fracture process of rock and soil engineering materials, to reveal the material failure process of nonlinear macroscopic mechanical behavior, evaluation of rock and rock engineering safe state to understand the stability of rock and soil engineering structure and take reasonable nursing measures. And the cracks can reflect directly the failure process of rock in the quantitative research on fracture. We usually need to choose a rupture criterion to determine rock modes under the action of force, such as the crack formation time and the direction of crack. Structural fracture often not appears as the single patterns. there is a crack, a conjugate shear fractures, and mix the two shear fracture. Therefore, actual research focus on criterion of tension fractures and shear fracture. In this paper, based on the analysis of the rock stress state, the fracture behavior of rock is analyzed from the theory of the Coulomb failure criterion and the Griffith fracture criterion. Then four different layers of silty mudstone were selected to carry out three axial compressive rock mechanics experiments. The fracture characteristics of rock under different confining pressures were studied. Finally, based on the stress strain test data, the fracture parameters of rock (cohesive force, internal friction angle) are calculated by using MATLAB software.
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An experimental study of micro-scale deformation in a soft sandstone

An experimental study of micro-scale deformation in a soft sandstone

Predicting the occurrence of failure in cohesive geomaterials by strain localisation is a key aspect in many geotechnical applications, e.g., drilling technology, nuclear waste disposal and sequestration of carbon dioxide. Previous studies have shown that the failure mechanisms in porous soft rocks are highly dependent on the stress level (e.g., Sulem and Ouffroukh, 2006; Bésuelle et al., 2000). Deformation bands have mechanical and structural evolutions that distinguish them from fractures and slip surfaces and in the case of permeability reduction, these bands could act as barriers to fluid flow in otherwise more permeable rock, impacting extraction and storage of fluids (e.g., Issen and Rudnicki, 2000; Fossen et al., 2007). This study investigates the deformation of a soft sandstone tested in triaxial compression at different confining pressures and the micro-scale mechanisms associated to the macroscopic behaviour.
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Numerical study of fracture network evolution during nitrogen fracturing processes in shale reservoirs

Numerical study of fracture network evolution during nitrogen fracturing processes in shale reservoirs

Several numerical models have been developed to investigate fracture behaviors during the hydraulic fracturing process. These models include the boundary element method [28], finite element method [29–31], and discrete element method [32,33]. Wang et al. [29] applied a new mathematical model to investigate fracture network evolution of multi-stranded fractures with pre-existing natural fractures. Shalev and Lyakhovsky [31] studied the damage evolution and seismicity phenomenon in hydraulic fracturing using an improved damage model based on the finite element method. However, there are still only a few studies on a numerical model for nitrogen fracturing and the comparison between water fracturing and nitrogen fracturing. On the other hand, shale reservoirs occur at different depths and are subject to different tectonic stress patterns. The in-situ stress state has important effects on hydraulic fracturing, which has been investigated since 1961 [28,34,35]. The breakdown pressure increases with confining pressure [36], and decreases with deviatoric stress during hydraulic fracturing [4]. Furthermore, vertical and horizontal geostresses vary with the stratum depth [37]. The concept of stress ratio is introduced to define the ratio of vertical geostress to horizontal geostress, which gradually decreases with the stratum depth [38]. It is found that the stress ratio plays an important role in fracture behavior during hydraulic fracturing [34,39,40]. Fractures generally initiate and propagate normal to the maximal principal stress. Thus, the evolution and effectiveness of fracture networks are related to the changing stress ratio [29,41]. However, most of these studies focused on the hydraulic fracturing and the impact of stress ratio on nitrogen fracturing has not been well studied.
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A Technical Review on Shale Gas Production and Unconventional Reservoirs Modeling

A Technical Review on Shale Gas Production and Unconventional Reservoirs Modeling

Unconventional resources inherent several specific characteristics, such as very low porosity, permeability, non-Darcy flow, rock surface desorption. All of this affects different aspects of shale from recovery to modeling, simulation and enhancing recovery methods. Most important parameter in shale is considered rock surface de- sorption that must be well established through experimental data since it makes a big different if it would have been ignored through reserve estimation and future production forecasting [2] [3]. Some studies have suggested that gas desorption from shale rock surface may contribute to extra gas production for EUR from shale gas re- servoirs. Cipolla et al. [4] [5] has reported that gas desorption contain up to 22% of the total gas production in 30-year period of production for two major producer in the US, Barnett shale and Marcellus shale. The signifi- cant impact of natural gas desorption is primarily seen during the later time of shale horizontal well production that mainly depends on, among other factors, shale reservoir permeability, flowing bottom hole pressure, and hy- draulic fracture spacing. State of the art of literature has shown in average that gas desorption contributes to 20% increase in the EUR during 30-year production performance forecasted for Marcellus shale well that is com- pleted with 12 stages of hydraulic fracturing [6].
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A Study on Effect of Fly Ash and Glass Powder...

A Study on Effect of Fly Ash and Glass Powder...

All the experimental data shows that the addition of the industrial wastes improves the physical and mechanical properties. These results are of great importance because this kind of innovative concrete requires large amount of fine particles . Due to its high fines of quarry dust it provided to be very effective in assuring very good cohesiveness of concrete. From the above study it is concluded that the mixture of fly ash and glass powder may be used as a partial replacement material for cement. Mixture of fly ash and glass powder has been used for different activities in the construction industry such as for road construction and manufacture of building materials such as light weight aggregates, bricks, tiles and auto clave blocks. However its use as rigid payment is very much limited. Thorough reaction with the concrete admixture, mixture of fly ash and glass powder, improved pozzolanic reaction, micro aggregate filling and concrete durability. As the properties are good as, the mixture of fly ash and glass powder is used as partial replacement of cement in the cement concrete.
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COMPARISON OF FRACTURE RESISTANCE OF CAD/CAM INTERIM BRIDGE AND CONVENTIONAL INTERIM RESIN BRIDGE

COMPARISON OF FRACTURE RESISTANCE OF CAD/CAM INTERIM BRIDGE AND CONVENTIONAL INTERIM RESIN BRIDGE

Background: Interim fixed restorations are important to protect pulp, protect abutment after preparation, assess the parallelism, preventing migration of abutments and improve esthetic appearance in anterior region. Moreover interim prostheses could assist in periodontal therapy, orthodontic therapy, occlusal treatment and implant therapy. Essentially, it should have good resistance to fracture, especially when used for extended treatment periods. Objective: evaluate and compare the fracture resistance between Cad/ Cam interim bridges and conventional interim bridges. Material and Method: Ideal model of full dental arch was used as a pattern to simulate three Units Bridge with (maxillary first molar and maxillary first premolar) as abutments. This model was then duplicated and resulted cast sectioned by cutting disk to produce a small cast that limited to the prepared bridge area only. This cast was then duplicated and poured by molten wax to produce wax pattern that was modified before casting with the use of radial shoulder finishing line design instead of chamfer finishing line that came with the original ideal model. From this wax pattern, metal master model was produced by lost wax technique. Thirty two impressions for master model with two stage putty- wash impression technique were taken and poured with die stone to produce thirty two stone models. The stone models then divided into four groups with eight models per group, according to the material and fabrication technique used to produce interim bridge and as follow: Group 1: Ivoclar CAD CAM (Telio CAD); Group 2: Ivoclar conventional (Telio Lab); Group 3: Vita CAD CAM(Vita CAD-Temp) and Group
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Quantitative Characterization and Dynamic Law of Interlayer Interference for Multilayer Commingled Production in Heavy Oil Reservoirs by Numerical Simulation

Quantitative Characterization and Dynamic Law of Interlayer Interference for Multilayer Commingled Production in Heavy Oil Reservoirs by Numerical Simulation

DOI: 10.4236/wjet.2019.73028 381 World Journal of Engineering and Technology will be shielded along the high permeability layer, and the residual oil is formed, which seriously affects the efficiency of water flooding and the recovery of oil field [7] [8] [9]. Yu Huili et al . [10] qualitative analysis the main controlling fac- tors of interlayer interference at different water cut stages, with the application of various data of dynamic production, coring inspection chamber, log interpre- tation data and fined reservoir research. Xian Bo et al . [11] obtained the degree of interlayer interference, technical countermeasures of eliminating the interfe- rence and corresponding technical chart for commingled production in thin re- servoirs by using dual model without interlayer channeling, numerical simula- tion and analysis of single and orthogonal factors. However, the effect of different pressure coefficient and formation permeability is only considered. Wang Shibo et al . [12] through the numerical simulation test, the influence degree of various factors on recovery can be obtained, and the oil recovery of various factors can be obtained by regression. When there is no interlayer interference well testing, Liu Hongjie [13] proposed using reservoir engineering method to calculate in- terlayer interference coefficient with DST test data, dynamic performance data, pressure buildup test interpretation results, PVT and core analysis results, and so on. In view of the present few theoretical researches on the quantitative charac- terization of interlayer interference in multi-layer commingled sandstone reser- voirs, Su Yanchun et al . [14] proposed a new concept of interlayer dynamic in- terference, and established a mathematical model for the quantitative characte- rization of the dynamic interference coefficient between layers. The quantitative relationship between the dynamic interference coefficient of the multi-layer com- bined production sandstone reservoir and the water content of the longitudinal layers, the permeability and the pressure difference of the combined production pressure is deduced by the seepage theory. However, the research only analyzed the influence of formation permeability and formation crude viscosity on pro- duction capacity interference factor ( PIIF ), the oil recovery interference factor ( RIIF ) is not analyzed.
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Chemical Structure of Kerogen of Shale Formations. (By the Example of the Shale Formations of the East European Platform)

Chemical Structure of Kerogen of Shale Formations. (By the Example of the Shale Formations of the East European Platform)

The study of the chemical structure of kerogenes of J3v2 oil shales (II-S type) and D3dm carbon rocks (II type) of the EEP allowed identifying the main distinctive features in the structure of individual structural components of these types of kerogen and refining the models of the fragment of their chemical structure. The J3v2 kerogen of oil shales is more highly aliphatic (H/QF = 1.32), the n-alkyl constituents of which are bound to the matrix predominantly through sulfur and oxygen atoms, compared to D3dm kerogen with an average atomic ratio (H/Qp) = 1.19. Some of the oxygen- containing structures are found to be present in the Middle Volga kerogen as carbohydrate moieties and algaenan components, the alkyl chains in which are interlinked by ether bonds, and the structure of the sulfur-containing components can be represented as sulfide(polysulfide)bound n-alkyl structures, in pyrolysis of which low-molecular and high-molecular alkyl-substituted thiophenes, thienyl- and phenylthiophenes are formed. The average S/C value exceeding 0.04 classifies the Upper Jurassic kerogen as Type II-S.
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Study of Concrete under the Action of Hydraulic fracturing in Ⅰ - Ⅱ mixed mode fracture criterion

Study of Concrete under the Action of Hydraulic fracturing in Ⅰ - Ⅱ mixed mode fracture criterion

Abstract: This paper simulates the concrete under the action of hydraulic fracturing in Ⅰ-Ⅱ mixed mode fracture. Double-K fracture criterion results in two different loading modes, that is, crack initiation and instability. According to Prefabricated crack and width of the specimen, experimental study of hydraulic fracturing, and the two different loading modes fracture of the specimen were fitted by making the angle formed by the four batches of 24 specimens to be 0°, 30°, 45° and 60° respectively. Axial tensile specimens is applied using hydraulic pressure loading, the crack tip paste the half-bridge strain gages and mounted clip-on extensometer for measurement of crack initiation, extension length and crack opening displacement, the specimen on the two side of water pressure sensor for measuring the extension of the fracture pressure. The total fracture toughness is calculated using overlay method from double-K fracture parameters that is water pressure and axial loads. Study found that, Ⅰ-Ⅱ mixed mode fracture study used two
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AF4A9648C8A1D3FE385AFBCA4DD1B4C pdf

AF4A9648C8A1D3FE385AFBCA4DD1B4C pdf

Shakespear demonstrated that the permeability of a gas is independent of the presence of other permeating gases for rubbery polymers at low pressures.19 This result has been verified by [r]

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Modeling and Simulation of Natural Gas Production from Unconventional Shale Reservoirs

Modeling and Simulation of Natural Gas Production from Unconventional Shale Reservoirs

The aim of this study is proposed a new reservoir model with incorporating all the flow mechanisms. We veri- fied our model with actual field data. Moreover, it is also essential to identify different mechanisms effect on production in long-term. For this purpose the history matched model is employed in our parameter sensitivity analysis, since it perfectly represents in-situ conditions. Langmuir and BET adsorption models, gas slippage and existence of natural fractures effects on cumulative production are evaluated independently in this section. 25 years of production time is selected for each condition, and our newly developed semi-analytical model is used to predict cumulative production performance. Table 3 includes the parameters and their ranges used in the pa- rameter analysis.
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Evaluation of Gas Reservoir of the Meghna Gas Field, Bangladesh Using Wireline Log Interpretation

Evaluation of Gas Reservoir of the Meghna Gas Field, Bangladesh Using Wireline Log Interpretation

greater than 1.0, then hydrocarbon will not move within the well. If the saturation index is less than 0.7 (for sandstone), hydrocarbon is moveable [29]. Hydrocarbons are moveable in the study well because all the calculated values are less than 0.7. It is important to know that BVW whether the formation is at irreducible water saturation or not using Morris and Biggs [26] equation. If The BVW ranges from 0.035 to 0.07, the grain size is fine to very fine-grained sand [30]. Bulk volume of water is nearly constant with some minor scattering in the hydrocarbon-bearing zones which indicate that the water free hydrocarbon (Table 4).
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Study of Weak Electric Current Emissions on Cement Mortar under Uniaxial Compressional Mechanical Stress up to the Vicinity of Fracture

Study of Weak Electric Current Emissions on Cement Mortar under Uniaxial Compressional Mechanical Stress up to the Vicinity of Fracture

An experimental technique that deals with the detection of weak electric signals emitted during the application of temporal uniaxial stress on solid materials has been applied on cement mortar samples. These electric signals are met in the literature as Pressure Stimulated Currents (PSC). Two different stress techniques were applied: uniaxial compressional stress at a) a low and b) at a high rate. Both qualitative and quantitative characteristics of the PSC are correlated with the mechanical state of the samples with respect to crack creation and propagation in the bulk of the material and consequently with the stages of composite damage.
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Properties Investigation on Chip on Film (COF) Thermosonic Bonding Using Anisotropic Conductive Films (ACFs)

Properties Investigation on Chip on Film (COF) Thermosonic Bonding Using Anisotropic Conductive Films (ACFs)

COF TS bonding was carried out using an ultrasonic bonder (Model: Fineplacer-LAMDA, FINETECH Co., Germany). Figure 2 shows the COF TS bonding process. The Si chip and PI fl exible substrate were carefully cleared using an organic solvent in order to remove any contaminants before the bonding process. The ACF was attached onto the cleaned PI flexible substrate and pre-bonding was carried out with 1 MPa of light pressure and a low temperature of approximately 353 K. After the pre-bonding process, the protecting film on the ACF was removed. The Si chip and PI flexible substrate were aligned and the mounted Si chip was then bonded at the predetermined temperature and pressure with ultrasonic vibrations. The frequency and amplitude of the ultrasonic vibrations were 40 kHz and 2 µm, respectively. In order to investigate the mechanical electrical properties of the COF assembly, the bonding temperature and dwell time of the ultrasonic vibrations were explored as bonding parameters. The three kinds of bonding temperature con- ditions of 413, 433 and 453 K had been determined. The two kinds of dwell time of ultrasonic vibrations of 0.5 and 1 s were applied to each of the temperature conditions. Table 2 shows the experimental conditions for the COF TC and TS
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Simultaneous measurements of elastic wave velocities and electrical conductivity in a brine-saturated granitic rock under confining pressures and their implication for interpretation of geophysical observations

Simultaneous measurements of elastic wave velocities and electrical conductivity in a brine-saturated granitic rock under confining pressures and their implication for interpretation of geophysical observations

We firstly consider the shape of pores in granite rock samples on the basis of the confining pressure depend- ence of velocities. For simplicity, a pore is supposed to have a spheroidal shape. The closure pressure given by Eq. (1) depends on its aspect ratio and elastic properties of the solid matrix. Since the influence of pores on elas- tic properties is sufficiently suppressed at high pressures, elastic properties of the solid phase are estimated from velocities in a dry rock sample (AJG02) at 177 MPa (Table 2). The pores closed below 125 MPa must thus have aspect ratios less than 2 × 10 − 3 . Such oblate spher- oidal pores can be treated as circular cracks, and their influence on velocities are formulated in terms of the crack density parameter defined by
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Damaged Concrete Wall and Leak Rate under Simulated Conditions

Damaged Concrete Wall and Leak Rate under Simulated Conditions

The experimental instantaneous transposition ratio (6) between the air flow at ambient temperature (noted ) and the air plus vapour plus liquid flow during accidental conditions (noted ) can be theoretically defined at any moment, the origin of the time being the beginning of the tests, in both cases the mass flow was considered (kg/h). The level of applied pressure was an essential element for the mass transfers. So to compare the two situations with the same historic of pressure, a special scenario T1 bis (air permeability test) was applied on the A and B specimens, the effective pressure following the pressure given on Figure 7 for scenario T2. Obviously, the scenario T1 bis was realized before the scenario T2.
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Studies of Fracture Damage Caused by Proppant Embedment Phenomenon in Shale Rock

Studies of Fracture Damage Caused by Proppant Embedment Phenomenon in Shale Rock

Effective packed fracture with the proppant for cylindrical steel plugs and shale rock 449. 450[r]

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Evaluation of glass fibre post with varying ferrule lenghts

Evaluation of glass fibre post with varying ferrule lenghts

post showed higher mean fracture resistance than teeth restored in group I GFR post and these findings are similar to study done by Sreedevi and Sanjeev (2015). The cast post showed the higher mean fracture resistance because it reproduces the morphology of the post space leading to maximum adaptation to canal (Zhi-Yue and Yu-Xing, 2003) (Gluskin et al., 1995). In each group there was significantly increase in fracture resistance with increase of ferrule length from 0mm to 1mm because of the crown ferrule formation which provides resistance to dislodgement and prevents fracture by bracing the tooth. Sorensen and Engelman (1990), Loney et al. (1990), Table 1. Fracture resistance of various ferrule lengths in Group A restored with glass fibre post and composite core and group B
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Elastic brittle plastic behaviour of shale reservoirs and its implications on fracture permeability variation: an analytical approach

Elastic brittle plastic behaviour of shale reservoirs and its implications on fracture permeability variation: an analytical approach

in horizontal effective stress, which can be defined as the mean of the change in the radial and tangential components of effective stress. As illustrated in Fig. 2a, any element of rock (i.e. at a specific value of r ) can be conceptualised as a hybrid of fractures and matrix blocks and any change in stress state (due to pore pressure reduction and swelling/ shrinkage effects) results in a change in the aperture size of the fractures within that element. Equation 12 therefore provides an efficient method for relating the response of frac- tures and their permeability at fracture scale to the changes in effective stress at field scale. The use of mean horizontal effective stress implies a matchstick matrix model, which is consistent with the plane-strain assumption. Closed-form solutions of permeability and porosity can then be obtained by substituting the stress and strain equations for different loading and boundary conditions into the above equations. It should be noted, however, that experimental results have shown that the relationship between post-failure permeabil- ity and the stress–strain state can be much more complex than what these models offer (e.g. Carey et al. 2015). How- ever, due to the lack of dedicated post-failure models, this widely used simplified approach was adopted in this paper. Limitations of the model are discussed later in the paper.
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Evaluation of curing condition on the high Strength concrete durability: Bangladesh perspective

Evaluation of curing condition on the high Strength concrete durability: Bangladesh perspective

A vast quantity of OPC (Ordinary Portland Cement) is produced in every year and utilized for the edifice of building, highways, roads and many other purposes but in constructional works and structural low quality cement may source of properties and lives loss So, quality guarantee of OPC is an critical and important concern. Chemical apparatus in Portland cement are made from diverse potential composites. The quantity of these potential composites are liable for diverse material properties of those cement. Four major composites of Portland cement are C 2 S, C 3 S, C 3 A, and C 4 AF but most important composites are the C 2 S, silicates, C 3 S
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