Letteratura scientifica selezionata sul tema "Fracture mechanics"
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Articoli di riviste sul tema "Fracture mechanics"
1
Zhang, Hai Yong, Shun Li He, Guo Hua Luan, Qiao Lu, Shao Yuan Mo, Zhang Zhang e Gang Lei. "Influence of Fracture Parameters on the Productivity of Fractured Horizontal Well Based on Fluid Mechanics in Tight Gas Reservoir". Advanced Materials Research 886 (gennaio 2014): 452–55. http://dx.doi.org/10.4028/www.scientific.net/amr.886.452.
Testo completoAbstract (sommario):
Multiple fractures are needed by hydraulic fracturing in order to improve the horizontal well productivity of a single well in tight gas reservoir. The calculation accuracy of productivity influences on the fracturing optimization results and the success ratio and effectiveness of fracturing treatment. This work focuses on analyzing the influence of fracture parameters on fractured horizontal well productivity in tight gas reservoir through establishing a productivity prediction model of fractured horizontal well, considering the interference between fracture and fracture and the wellbore pressure drop. Results show that the fracture parameters, such as fracture number, fracture interval, fracture conductivity and fracture length, have different influences on the productivity of fractured horizontal well and thus, the effects of fracture parameters should be taken into account when designing the fracturing treatment.
2
Shi, Di, Liping Li, Jianjun Liu, Mingyang Wu, Yishan Pan e Jupeng Tang. "Effect of discrete fractures with or without roughness on seepage characteristics of fractured rocks". Physics of Fluids 34, n. 7 (luglio 2022): 073611. http://dx.doi.org/10.1063/5.0097025.
Testo completoAbstract (sommario):
This study proposes a new fractal permeability model for fractured rocks that comprehensively accounts for the geometric fracture characteristics and the fluid transport mechanism. Then, the permeability changes of fractured rocks are analyzed using discrete fracture networks (DFNs) with or without roughness and different geometry parameters in the DFN modeling and finite element simulation. The results show that the proposed permeability model well agrees with the experimental data, and the established DFN numerical model more realistically reflects the fracture network in fractured rocks. Fluctuation of tortuous fracture lines (rough fractures) increases the fracture intersection probability, consequently increasing the fracture intersection area or connecting adjacent fractures. Moreover, permeability increases with the fractal dimension Df, porosity ϕ, maximum fracture length lmax, and proportionality coefficient β, and it decreases with increasing fractal dimension DTf of fracture tortuosity. When the fracture proportionality coefficient is 0.001 ≤ β ≤ 0.01, different DFNs yield similar simulation results for permeability. However, with increasing fracture network complexity, the predictive model created using conventional DFN (C-DFN) increasingly overestimates the fractured rock permeability. Thus, building a permeability model for a fractured rock using rough DFN (R-DFN) is more effective than that using C-DFN. Our findings are helpful for real permeability predictions via DFN and analytical modeling.
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VanCourt, RB, SE Byron, SJ Ali e BD Caldwell. "Fracture mechanics. A comparison study of torsional stress on bone". Journal of the American Podiatric Medical Association 90, n. 4 (1 aprile 2000): 167–74. http://dx.doi.org/10.7547/87507315-90-4-167.
Testo completoAbstract (sommario):
Fractures that result from torsional loading of shafts in mechanical systems of nonbiologic materials generate a fracture line that forms a 45 degrees angle to an axis that is perpendicular to the direction of torsional loading on the shaft. As tension and compression are applied to these isotropic substances, the angle of fracture increases and decreases, respectively. Understanding how these forces, particularly compressive forces, generate elongation of a spiral fracture increases the ability to predict the extent of injury to bone. Fibular and metatarsal fractures are of primary importance to the podiatric physician, but any spiral fracture may be subject to torsional loading. Thus the principles stated here apply to the entire skeletal system. The purpose of this article is to provide a better understanding of the mechanics behind the causes and characteristics of fractures and to explore whether these same factors apply to the fracture mechanics of bone.
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Yuan, Yingzhong, Wende Yan, Fengbo Chen, Jiqiang Li, Qianhua Xiao e Xiaoliang Huang. "Numerical Simulation for Shale Gas Flow in Complex Fracture System of Fractured Horizontal Well". International Journal of Nonlinear Sciences and Numerical Simulation 19, n. 3-4 (26 giugno 2018): 367–77. http://dx.doi.org/10.1515/ijnsns-2017-0135.
Testo completoAbstract (sommario):
AbstractComplex fracture systems including natural fractures and hydraulic fractures exist in shale gas reservoir with fractured horizontal well development. The flow of shale gas is a multi-scale flow process from microscopic nanometer pores to macroscopic large fractures. Due to the complexity of seepage mechanism and fracture parameters, it is difficult to realize fine numerical simulation for fractured horizontal wells in shale gas reservoirs. Mechanisms of adsorption–desorption on the surface of shale pores, slippage and Knudsen diffusion in the nanometer pores, Darcy and non-Darcy seepage in the matrix block and fractures are considered comprehensively in this paper. Through fine description of the complex fracture systems after horizontal well fracturing in shale gas reservoir, the problems of conventional corner point grids which are inflexible, directional, difficult to geometrically discretize arbitrarily oriented fractures are overcome. Discrete fracture network model based on unstructured perpendicular bisection grids is built in the numerical simulation. The results indicate that the discrete fracture network model can accurately describe fracture parameters including length, azimuth and density, and that the influences of fracture parameters on development effect of fractured horizontal well can be finely simulated. Cumulative production rate of shale gas is positively related to fracture half-length, fracture segments and fracture conductivity. When total fracture length is constant, fracturing effect is better if single fracture half-length or penetration ratio is relatively large and fracturing segments are moderate. Research results provide theoretical support for optimal design of fractured horizontal well in shale gas reservoir.
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Kubeyev, Amanzhol, Nathaniel Forbes Inskip, Tomos Phillips, Yihuai Zhang, Christine Maier, Kevin Bisdom, Andreas Busch e Florian Doster. "Digital Image-Based Stress–Permeability Relationships of Rough Fractures Using Numerical Contact Mechanics and Stokes Equation". Transport in Porous Media 141, n. 2 (gennaio 2022): 295–330. http://dx.doi.org/10.1007/s11242-021-01719-7.
Testo completoAbstract (sommario):
AbstractFlow in fractures is sensitive to their geometrical surface characteristics. The surface can undergo deformation if there is a change in stress. Natural fractures have complex geometries and rough surfaces which complicates the modelling of deformation and fluid flow. In this paper, we present a computational model that takes a digital image of a rough fracture surface and provides a stress–permeability relationship. The model is based on a first-principle contact mechanics approach at the continuum scale. Using this first principle approach, we investigate numerically the effect of fracture surface roughness and shifting of surfaces on the permeability evolution under applied stress and compare the results with laboratory experiments. A mudrock core fracture surface was digitalized using an optical microscope, and 2D cross sections through fracture surface profiles were taken for the modelling. Mechanical deformation is simulated with the contact mechanics based Virtual Element Method solver that we developed within the MATLAB Reservoir Simulation Toolbox platform. The permeability perpendicular to the fracture cross section is determined by solving the Stokes equation using the Finite Volume Method. A source of uncertainty in reproducing laboratory results is that the exact anchoring of the two opposite surfaces is difficult to determine while the stress–permeability relationship is sensitive to the exact positioning. We, therefore, investigate the sensitivity to a mismatch in two scenarios: First, we assess the stress–permeability of a fracture created using two opposing matched surfaces from the rock sample, consequently applying relative shear. Second, we assess the stress–permeability of fractures created by randomly selecting opposing surfaces from that sample. We find that a larger shift leads to a smaller drop in permeability due to applied stress, which is in line with a previous laboratory study. We also find that permeability tends to be higher in fractures with higher roughness within the investigated stress range. Finally, we provide empirical stress–permeability relationships for various relative shears and roughnesses for use in hydro-mechanical studies of fractured geological formations.
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Wang, Yonggang, Xuejuan Zhang, Jie Zhang, Yali Zeng, Lei Zhang, Han Wang e Ruolin Li. "Comparative Study on Artificial Fracture Modeling Schemes in Tight Reservoirs—For Enhancing the Production Efficiency of Tight Oil and Gas". Energies 17, n. 20 (21 ottobre 2024): 5235. http://dx.doi.org/10.3390/en17205235.
Testo completoAbstract (sommario):
In order to improve the reliability of the deployment of production schemes after artificial fracturing in tight reservoirs, it is urgent to carry out research on the description of fractures after artificial fracturing. In this study, taking the Chang 61 oil formation group in the Wangyao South area of Ordos Basin as an example, three different fracture modeling schemes are used to establish the geological model of fractured reservoirs, and the fitting ratios of the respective reservoir models are calculated by using the method of reservoir numerical simulation of the initial fitting, and the optimal fractured reservoir modeling scheme is screened in the end. The research area adopts three types of fracture prediction results based on FMI fracture interpretation data, seismic fracture prediction data, and rock mechanics artificial fracturing simulation data. On this basis, geological models of fractured reservoirs are established, respectively. The initial fitting of reservoir values of each geological model are compared, and the highest initial fitting rate of reservoir values is 88.44%, which is based on rock mechanics artificial fracturing simulation data. However, the initial fitting rate of the reservoir model was the lowest at 75.76%, which was established based on the fracture random modeling results of FMl fracture interpretation data. Under the constraints of seismic geostress prediction results and microseismic monitoring data, the simulation results of rock mechanics artificial fracturing fracture are used as the basis, on which the geological model of artificially fractured reservoirs is thus established, and this scheme can more realistically characterize the characteristics of fractured reservoirs after artificial fracturing in the study area.
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Yu, Chaoyun, Bin Gong, Na Wu, Penglei Xu e Xiankai Bao. "Simulation of the Fracturing Process of Inclusions Embedded in Rock Matrix under Compression". Applied Sciences 12, n. 16 (11 agosto 2022): 8041. http://dx.doi.org/10.3390/app12168041.
Testo completoAbstract (sommario):
Typical parallel fractures are often observed in the outcrops of inclusions in the field. To reveal the failure mechanism of inclusions embedded in rock matrix, a series of heterogeneous models are established and tested based on the damage mechanics, statistical strength theory, and continuum mechanics. The results show that, with the spacing between two adjacent fractures decreasing, the stress is firstly transferred from negative to positive, then from positive to negative. Stress transition is profound for the fracture spacing. Meanwhile, three types of fractures, i.e., consecutive fracture, non-consecutive fracture, and debonding fracture, are found, which are consistent with the observed modes in the field. Multiple inclusions are often fractured easier than an isolated inclusion due to the stress disturbance between inclusions and newly generated fractures. Either in single or multiple inclusions, tensile stresses inside the inclusions are the main driving force for fracture initiation and propagation. Besides, although the material heterogeneity has a small effect on the stress variation, it has an evident impact on the fracturing mode of inclusions. The stiffness ratio is critical for the stress transition and failure pattern; the interface debonding occurs earlier than the fracture initiation inside the inclusion when the stiffness ratio is relatively high. Additionally, the inclusions content only affects the sequence of fracture initiation rather than the final fracture spacing pattern.
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Abass, Hazim Abass, Chris Lamei Lamei, Kaveh Amini Amini e Tadesse Teklu Teklu. "Hydraulic Fracturing Tight Reservoirs: Rock Mechanics and Transport Phenomena". Journal of Petroleum Research and Studies 8, n. 2 (6 maggio 2021): 122–43. http://dx.doi.org/10.52716/jprs.v8i2.239.
Testo completoAbstract (sommario):
Conventional reservoirs have been fracture stimulated using acid fracturing and proppant fracturing.Acid fracturing is performed to improve well productivity in acid-soluble formations such aslimestone, dolomite, and chalk. Hydrochloric acid is generally used to create an etched fracture,which is the main mechanism for maintaining the fracture open during the life of a well. Proppantfracturing is an alternative option that has been applied in carbonaceous and siliceous formations.There is no quantitative method to provide an answer of whether acid fracturing or proppantfracturing is an appropriate stimulation method for a given carbonate formation. How rockmechanics can be applied to decide on what method is more effective? Laboratory experiments havebeen performed to simulate acid etched to study the effect of elastic, plastic and viscoelastic rockbehavior and their effects on fracture conductivity. Comparison of acid vs. proppant fracturingconductivity in carbonate formation is presented.Fracturing low permeability reservoirs is totally different than fracturing tight formations. Thefracture geometry required in low permeability reservoirs need to be planar, conductive andpenetrating deep in the reservoir. Fracture complexity in these reservoirs is to be avoided foroptimum stimulation treatment. However, in fracturing tight formation, a complex fracture networkis desirable for better recovery. Creating multiple fractures in horizontal wells without the use ofmechanical intervention, is becoming essential especially in tight gas reservoirs. We have learnedhow to initiate hydraulic fractures into a specific direction and place as many fractures as desired inhorizontal wells but with casing and perforation. The challenge now is to initiate weak point acrossthe horizontal well such that fracturing fluid will initiate a fracture there. How rock mechanics hasbeen applied to achieve this objective? We are fracturing tight gas sand in harsh environment, atdepth more than 18000 ft, of temperature close to 400 °F, and one can figure out the extreme in-situstresses relevant to this depth.When the reservoir pressure decreases, the elastic displacement in response to the increase ineffective stress will cause natural fractures to close leading to a decline in reservoir productivity.
The matrix medium feeds the natural tensile fractures which carry the fluids to the wellbore. Thedecline in conductivity with increasing effective stress should follow a logical declining rate tosupport a given production rate. How the concept of effective stress has been applied to understandthe stress-dependent conductivity of various conductive components of a given reservoir? Rockmechanics testing of these stress sensitive reservoirs becomes vital to optimize fracturing tightformations.Economical production from tight reservoirs, including shale gas and shale oil formations, requireshorizontal well drilling and massive proppant hydraulic fracturing stimulation. The stimulationinvolves generating sufficient fractures network or stimulated reservoir volume (SRV), which isachieved by placing optimized stimulation treatments along the horizontal section of wellboresideally drilled from multi-well pads to increase the production rate and ultimate recovery. Hydraulicfracturing in naturally fractured formations is characterized by generating a fractures’ network thatshould be designed for in extremely low permeability of unconventional reservoirs. Fractures shouldextensively reach shale matrix to achieve commercial gas production. Therefore, production rate andultimate recovery depend on the size of the created SRV.The transport phenomena controlling fluid flow through tight formation is no longer sufficient to bemodeled by Darcy’s flow. Diffusion and imbibition are important transport mechanisms. The conceptof osmosis and flow through a semi-permeable membrane component are critical. Additionally,diffusion and a special case of molecular flow due to Knudson effect will be discussed. Conventionalreservoir simulation collapses when trying to simulate fluid flow through tight reservoirs. Numericalstudies on a hydraulically fractured well to simulate the dynamic processes during fracturinginjection, following well shut-in (soaking), and production are discussed.
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Chen, Peng, Shuhan Yang, Xinyu Chen, Zeyu Li, Chuanbo Shen e Huaning Qiu. "Multiscale Characterization of Fractures and Analysis of Key Controlling Factors for Fracture Development in Tight Sandstone Reservoirs of the Yanchang Formation, SW Ordos Basin, China". Applied Sciences 14, n. 21 (23 ottobre 2024): 9676. http://dx.doi.org/10.3390/app14219676.
Testo completoAbstract (sommario):
Tight sandstone reservoirs, despite their low porosity and permeability, present considerable exploration potential as unconventional hydrocarbon resources. Natural fractures play a crucial role in hydrocarbon migration, accumulation, and present engineering challenges such as late-stage reformation in these reservoirs. This study examines fractures in the seventh member of the Triassic Yanchang Formation’s tight sandstone within the Ordos Basin using a range of methods, including field outcrops, core samples, imaging and conventional logging, thin sections, and scanning electron microscopy. The study clarifies the characteristics of fracture development and evaluates the relationship between dynamic and static rock mechanics parameters, including the calculation of the brittleness index. Primary factors influencing fracture development were quantitatively assessed through a combination of outcrop, core, and mechanical test data. Findings reveal that high-angle structural fractures are predominant, with some bedding and diagenetic fractures also present. Acoustic, spontaneous potential, and caliper logging, in conjunction with imaging data, enabled the development of a comprehensive probabilistic index for fracture identification, which produced favorable results. The analysis identifies four key factors influencing fracture development: stratum thickness, brittleness index, lithology, and rock mechanical stratigraphy. Among these factors, stratum thickness is negatively correlated with fracture development. Conversely, the brittleness index positively correlates with fracture development and significantly influences fracture length, aperture, and linear density. Fractures are most prevalent in siltstone and fine sandstone, with minimal development in mudstone. Different rock mechanics layer types also impact fracture development. These insights into fracture characteristics and controlling factors are anticipated to enhance exploration efforts and contribute to the study of similar unconventional reservoirs.
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McClure, Mark W., Mohsen Babazadeh, Sogo Shiozawa e Jian Huang. "Fully Coupled Hydromechanical Simulation of Hydraulic Fracturing in 3D Discrete-Fracture Networks". SPE Journal 21, n. 04 (15 agosto 2016): 1302–20. http://dx.doi.org/10.2118/173354-pa.
Testo completoAbstract (sommario):
Summary We developed a hydraulic-fracturing simulator that implicitly couples fluid flow with the stresses induced by fracture deformation in large, complex, 3D discrete-fracture networks (DFNs). The code is efficient enough to perform field-scale simulations of hydraulic fracturing in DFNs containing thousands of fractures, without relying on distributed-memory parallelization. The simulator can describe propagation of hydraulic fractures and opening and shear stimulation of natural fractures. Fracture elements can open or slide, depending on their stress state, fluid pressure, and mechanical properties. Fracture sliding occurs in the direction of maximum resolved shear stress. Nonlinear empirical equations are used to relate normal stress, fracture opening, and fracture sliding to fracture aperture and transmissivity. Fluid leakoff is treated with a semianalytical 1D leakoff model that accounts for changing pressure in the fracture over time. Fracture propagation is modeled with linear-elastic fracture mechanics. The Forchheimer equation (Forchheimer 1901) is used to simulate non-Darcy pressure drop in the fractures because of high flow rate. A crossing criterion is implemented that predicts whether propagating hydraulic fractures will cross natural fractures or terminate against them, depending on orientation and stress anisotropy. Height containment of propagating hydraulic fractures between bedding layers can be modeled with a vertically heterogeneous stress field or by explicitly imposing hydraulic-fracture-height containment as a model assumption. Limitations of the model are that all fractures must be vertical; the mechanical calculations assume a linearly elastic and homogeneous medium; proppant transport is not included; and the locations of potentially forming hydraulic fractures must be specified in advance. Simulations were performed of a single propagating hydraulic fracture with and without leakoff to validate the code against classical analytical solutions. Field-scale simulations were performed of hydraulic fracturing in a densely naturally fractured formation. The simulations demonstrate how interaction with natural fractures in the formation can help explain the high net pressures, relatively short fracture lengths, and broad regions of microseismicity that are often observed in the field during stimulation in low-permeability formations, and that are not predicted by classical hydraulic-fracturing models. Depending on input parameters, our simulations predicted a variety of stimulation behaviors, from long hydraulic fractures with minimal leakoff into surrounding fractures to broad regions of dense fracturing with a branching network of many natural and newly formed fractures.
Tesi sul tema "Fracture mechanics"
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Srivastava, Ankit. "Mechanics and Mechanisms of Creep and Ductile Fracture". Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283799/.
Testo completoAbstract (sommario):
The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-based superalloy specimens have shown size dependent creep response termed as the thickness debit effect. To investigate the mechanism of the thickness debit effect, isothermal creep tests were performed on uncoated Ni-based single crystal superalloy sheet specimens with two thicknesses and under two test conditions: a low temperature high stress condition and a high temperature low stress condition. At the high temperature, surface oxidation induced microstructural changes near the free surface forming a layered microstructure. Finite element calculations showed that this layered microstructure gave rise to local changes in the stress state. The specimens also contained nonuniform distribution of initial voids formed during the solidification and homogenization processes. The experiments showed that porosity evolution could play a significant role in the thickness debit effect. This motivated a basic mechanics study of porosity evolution in single crystals subjected to creep for a range of stress states. The study was performed using three-dimensional finite deformation finite element analysis of unit cells containing a single initially spherical void in a single crystal matrix. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for both primary and secondary creep. The effect of initial void spacing and creep exponent was also explored. Based on the experimental observations and results of finite element calculations a quantitative mechanistic model is proposed that can account for both bulk and surface damage effects and assess their relative roles in the observed thickness debit effect. Another set of calculations aim at relating the crack growth resistance and fracture surface morphology to material microstructure for ductile structural metals. The process that governs the ductile fracture of structural materials at room temperature is one of nucleation, growth and coalescence of micron scale voids, and involves large plastic deformations. Experimental studies have shown that fracture surfaces in a wide variety of materials and under a wide variety of loading conditions have remarkable scaling properties. For thirty years, the hope to relate the statistical characterization of fracture surfaces to a measure of a material's crack growth resistance has remained unfulfilled. Only recently has the capability been developed to calculate sufficient amounts of three dimensional ductile crack growth in heterogeneous microstructures to obtain a statistical characterization of the predicted fracture surfaces. This development has enabled the exploration of the relation of both fracture toughness and fracture surface statistics to material properties and microstructure when the fracture mechanism is one of void nucleation, growth and coalescence. The relation of both toughness and the statistical properties of fracture surfaces in calculations of heterogeneous microstructures to various microstructural features is discussed and a remarkable correlation between fracture surface roughness and fracture toughness is shown for the first time.
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Mansfield-Williams, H. D. "Mode 11 fracture mechanics in solid wood and fracture mechanics in laminated veneer lumber". Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390815.
Testo completo
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Tiernan, Declan Martin. "Collocation studies in fracture mechanics and quantum mechanics". Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318739.
Testo completo
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Denning, Shawn Patrick. "Fracture mechanics of sandwich structures". Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6809.
Testo completoAbstract (sommario):
Over the past few decades both the demand for knowledge as well an increase in the application of composite materials has boomed. This has led to an intensive focus by the research community to gather information and validate the use of such materials. Sandwich composites have been a particular interest and an intense demand for further understanding was sparked by the catastrophic rudder failure of Air Transat 961. This thesis focuses on understanding fracture mechanics and damage tolerance within sandwich composites. Facesheet disbond has severe impacts on the material systems strength and stiffness, and large disbonds can often lead to catastrophic component failure. Understanding how these disbonds grow is paramount to recognizing the limitations of sandwich composites.
This thesis has several objectives. First, determine the fracture toughness of various sandwich composite material systems under going quasi-static loading. Second, determine how variations within the material systems such as facesheet thickness, core type, cell size and core density effect the results. Third, determine how the failure modes such as adhesive, pullout and core alter the results. Fourth, determine how fluid ingression effects fracture toughness. Fifth, provide baseline data for further testing and modeling.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Matthews, C. "Fracture mechanics of volcanic eruptions". Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16280/.
Testo completoAbstract (sommario):
Seismology is a key tool in the forecasting of volcanic eruptions. The onset of an eruption is often preceded and accompanied by an increase in local seismic activity, driven by fracturing within the edifice. For closed systems, with a repose interval of the order of a century or more, this fracturing must occur in order to create a pathway for the magma to reach the surface. Time-to-failure forecasting models have been shown to be consistent with seismic acceleration patterns prior to eruptions at volcanoes in subduction zone settings. The aim of this research is to investigate the patterns in seismic activity produced by a failure model based on fundamental fracture mechanics, applied to a volcanic setting. In addition to the time series of earthquake activity, statistical measures such as seismic b-value are also analysed and compared with corresponding data from the field and laboratory studies. A greater understanding of the physical factors controlling fracture development and volcano-tectonic activity is required to enhance our forecasting capability. The one dimensional, fracture mechanics grid model developed in this work is consistent with the theory of growth and coalescence of multi-scale fractures as a controlling factor on magma ascent. The multi-scale fracture model predicts an initial exponential increase in the rate of seismicity, progressing to a hyperbolic increase that leads to eruption. The proposed model is run with variations in material and load properties, and produces exponential accelerations in activity with further development to a hyperbolic increase in some instances. In particular, the model reproduces patterns of acceleration in seismicity observed prior to eruptions at Mt. Pinatubo (1991) and Soufriere Hills (1995). The emergence of hyperbolic activity is associated with a mechanism of crack growth dominated by interaction and coalescence of neighbouring cracks, again consistent with the multi-scale fracture model. The model can also produce increasing sequences of activity that do not culminate in an eruption; an occurrence often observed in the field. Scaling properties of propagating fractures are also considered. The seismic bvalue reaches a minimum at the time of failure, similar to observations from the field and measurements of acoustic emissions in the laboratory. Similarly, the fractal dimension describing the fracture magnitude distribution follows trends consistent with other observations for failing materials. The spatial distribution of activity in the model emerges as a fractal distribution, even with an initially random location of fractures along the grid. Significant shifts in the temporal or spatial scaling parameters have been proposed as an indication of change in controlling factors on a volcanic system, and therefore represent a relatively unexplored approach in the art of eruption forecasting.
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Richardson, James Bruce. "The mechanics of fracture healing". Thesis, University of Aberdeen, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290866.
Testo completoAbstract (sommario):
The mechanics applied to healing fractures vary widely. At one extreme rigid internal fixation is advocated, while at the other early mobilisation is recommended using external splints. Kuhn's method of paradigm orientated research was used to define the historical context of current assumptions regarding fracture healing. Conflict between the various schools of thought is the main evidence for failure of these assumptions and the need to evolve a new perspective on fracture healing. A paradigm is presented which proposes healing by external callus as an early stage and 'primary healing' as the later stage as of one continuous but changing process. A fundamental hypothesis was tested: that mechanics is the major control of fracture healing in man. A multicentre study of 102 patients with serious fractures were treated with external skeletal fixation. In 60 patients rigid external fixation was applied. In the remaining 42 the same fixation device was used, but adapted to apply 1 to 2mm of cyclic axial micromovement across the fracture. A piston applied 500 cycles of movement over a 30 minute period each day until this could be achieved by the patient on weight-bearing. Objective assessment required development of new techniques of measuring fracture stiffness and defining the point of healing. This objective measure, and clinically defined healing, were significantly faster in the group treated with micromovement (two-way analysis of variance, p = 0.005 and 0.03, respectively). Repeated injury by plastic deformation is proposed to maintain callus growth in the first phase of healing. Evidence for the required parameters of movement was gathered from the trial of micromovement, from measurements in 4 cases of epiphyseolysis and also 8 patients undergoing arthrodesis. It would appear appropriate to apply cyclic axial displacement of 2mm within the first two weeks from injury and of consistent direction until sufficient bulk of callus is formed. Thereafter axial compaction is appropriate in a second phase where callus matures. The mechanics that govern remodelling were considered to apply to the final phase. Failure of a cell culture model to display obvious results from cyclic loading may indicate that the response to mechanical loading is indirect. Intermediate and mechanically dependent biochemical and bioelectrical factors are discussed.
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MacLennan, Iain James. "Two parameter engineering fracture mechanics". Thesis, University of Glasgow, 1996. http://theses.gla.ac.uk/6756/.
Testo completoAbstract (sommario):
The object of this work was to investigate and expand on previously carried out research into elastic-plastic crack tip fields using the first two terms of the Williams expansion to characterise the degree of crack tip constraint. As a precursor to this research a history of fracture mechanics is also presented. In the present work crack tip fields in small scale yielding have been detennined using modified boundary layer formulations in an attempt to model the influence of the second order term of the Williams expansion, the T -stress. The prime object of this thesis was to investigate and expand on previously carried out research into a two parameter characterisation of elastic-plastic crack tip fields using the second parameter of the Williams expansion(T), which attempts to characterise the degree of crack tip constraint. Modified Boundary Layer formulations in conditions of plane strain were implemented to derive a suitable reference solutions, against which the effects of out of plane strains can be compared and the validity of presently established reference fields can be gauged. The effect of out of plane non-singular stress, S, on the crack tip stress field were also considered, where constraint was largely determined by T. A wide range of analyses have been carried out, from the microstructural scale to complete engineering components in an attempt to characterise crack tip stress fields. The ability to apply two parameter fracture concepts to real engineering structures requires methods for calculating T for complex components with realistic semi-elliptical defects. A simple engineering method for achieving this was developed making use of linespring elements in the finite element package ABAQUS. This approach was validated by the calculation of T for semi-elliptical cracks at the chord-brace intersection of a tubular welded joint, modelled using the mesh generation program PATRAN. The micromechanics of cleavage, using the Ritchie-Knott-Rice model have also been constructed. This work relates the ratio of J for unconstrained and constrained geometries to critical microstructural distance, critical cleavage stress and the toughness ratio on the strainhardening effect. The elastic-plastic behaviour of short and deeply cracked bend bars has previously been described by Betegon and Hancock based on the first two terms of the Williams expansion. A local cleavage criterion has been applied to these fields to indicate the effect of loss of constraint on lower shelf toughness of shallow cracked bend bars. The work models the maximum temperature at which cleavage can occur in these geometries to show the effect of constraint and aJW ratio of cracked bend bars on the ductile-brittle transition temperature. This has also been backed by a significant experimental research program. Finally constraint dependent toughness has been considered in relation to failure assessment methodologies. A simple engineering method for modifying these Failure Assesssment Diagrams has been presented, this consists of considering the constraint matched toughness of the strucutre. This procedure recovers the original Failure Assessment Line and unifies the constraint dependent fracture toughness within defect assessment schemes which utilise Failure Assessment Diagrams.
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Jonsson, Anders. "Integral equation methods for fracture mechanics and micro-mechanical problems". Doctoral thesis, KTH, Solid Mechanics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3336.
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Stehn, Lars. "Tensile fracture of ice : test methods and fracture mechanics analysis". Doctoral thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 1993. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18394.
Testo completoAbstract (sommario):
This thesis is concerned with several aspects of fracture of both brackish (low salinity) sea ice and freshwater ice. The tests and analyses are confined to tensile, or in fracture mechanics language, Mode I, fracture. A large part of this thesis is dedicated to demonstrate that Linear Elastic Fracture Mechanics (LEFM) can be applicable on ice by laboratory and in-situ tests of defined specimens. All interpretations are made using the dicipline of LEFM.First, the development of a field test equipment called FIFT ( a Field Instrument for Fracture toughness Tests on ice) is described. The FIFT is used in both field and laboratory fracture toughness tests on brackish sea ice from the Gulf of Bothnia to describe porosity effects on the apparent fracture toughness, KQ, and estimate crack velocities. An appropriate speciment size, in terms of notch sensitivity, is then provided valid for grain sizes ranging from 1.6 to nearly 100 mm.An augmented use of the FIFT is then described where fracture toughness tests are performed on S1 type freshwater ice to investigate if similarities exist in the local KI fields for three different fracture geometries. The results indicate that, under comparable conditions, KQ is similar for all of the geometries. However, the type of specimen, has a marked influence on the character of the fracture surface.Then, the influence of structural anisotropy on the fracture toughness of S1 ice is investigated by fabricating and testing three different fracture geometries from a single ice core. This approach is suitable for both field and, as in this work, laboratory studies. There is a wide scatter in the KQ values. Possible explanations to the results are discussed in terms of the microstructural influences and specimen size effects.Finally, crack growth resistance measurements on large grained S1 ice is conducted. A new fracture geometry is used which is found to be extremely favorable of promoting stable, stick-slip, crack growth over a large portion of the uncracked ligament. Now a complete characterization of the fracture resistance curve is therefore possible, A negative fracture resistance KR-curve is evaluated for the S1 ice at -16°C.Godkänd; 1993; 20070426 (ysko)
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Liu, Guoning. "Application of fracture mechanics in electrical/mechanical failures of dielectrics /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LIU.
Testo completoLibri sul tema "Fracture mechanics"
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Zehnder, Alan T. Fracture Mechanics. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-94-007-2595-9.
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Miannay, Dominique P. Fracture Mechanics. New York, NY: Springer New York, 1998. http://dx.doi.org/10.1007/978-1-4612-1740-4.
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Gdoutos, Emmanuel E. Fracture Mechanics. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8158-5.
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Gdoutos, Emmanuel E. Fracture Mechanics. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-35098-7.
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Gross, Dietmar, e Thomas Seelig. Fracture Mechanics. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-71090-7.
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Perez, Nestor. Fracture Mechanics. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-24999-5.
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Papadopoulos, George A. Fracture Mechanics. London: Springer London, 1993. http://dx.doi.org/10.1007/978-1-4471-1992-0.
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Gross, Dietmar, e Thomas Seelig. Fracture Mechanics. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19240-1.
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J, Zuidema, e Wanhill R. J. H, a cura di. Fracture mechanics. 2a ed. Delft: DUP Blue Print, 2002.
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Zehnder, Alan T. Fracture Mechanics. Dordrecht: Springer Netherlands, 2012.
Cerca il testo completoCapitoli di libri sul tema "Fracture mechanics"
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Zhao, Yu, Yongfa Zhang e Pengfei He. "Formation of Complex Networks". In Hydraulic Fracturing and Rock Mechanics, 231–65. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2540-7_9.
Testo completoAbstract (sommario):
AbstractWhen a hydraulic fracture interacts with multiple natural fractures (such as bedding planes, faults, weak interlayers, and formation interfaces) in the formation, arrests, bifurcations, crossings, and openings may occur, contributing to forming a complex fracture network (referred as CFN). Shale differs from other types of rocks due to its apparent bedding anisotropy, making it easier to form complex fracture networks during hydraulic fracturing. A mass of field hydraulic fracturing data and laboratory studies have confirmed that the hydraulic fractures generated in shale reservoirs are not bi-wing planar fractures in homogeneous media, but multi-dimensional, asymmetric, and non-planar complex hydraulic fractures (as shown in Fig. 9.1) (Liu et al. in Guti Lixue Xuebao/Acta Mech Solida Sin 37:34–49, 2016; Xiao in Research of hydraulic fracturing dynamic propagation in fractured reservoirs, 2014; Guo and Wang in J Eng Geol 26:118–128, 2016).
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Cruse, T. A. "Fracture Mechanics". In Mechanics: Computational Mechanics, 7–15. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-1385-1_2.
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Zhao, Yu, Yongfa Zhang e Pengfei He. "Fracture Interaction Behaviors". In Hydraulic Fracturing and Rock Mechanics, 199–227. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2540-7_8.
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AbstractProblems arising from hydraulic fracturing involve the nonlinear coupling of rock deformation and fluid flow, the nonlocal character of the fracture elastic response, the time dependence of fracture propagation and the interacting interference between the pre-existing and induced fractures.
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François, Dominique, André Pineau e André Zaoui. "Fracture Mechanics". In Mechanical Behaviour of Materials, 7–102. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-94-007-4930-6_2.
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Munz, Dietrich, e Theo Fett. "Fracture Mechanics". In Ceramics, 19–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-58407-7_3.
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Kinloch, A. J., e R. J. Young. "Fracture Mechanics". In Fracture Behaviour of Polymers, 74–106. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-017-1594-2_3.
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Narasimhan, R. "Fracture Mechanics". In Lecture Notes in Engineering, 556–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83535-3_22.
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Öchsner, Andreas. "Fracture Mechanics". In Continuum Damage and Fracture Mechanics, 85–127. Singapore: Springer Singapore, 2015. http://dx.doi.org/10.1007/978-981-287-865-6_5.
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Leevers, P. S. "Fracture Mechanics". In Polymer Science and Technology Series, 96–101. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-015-9231-4_22.
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Gooch, Jan W. "Fracture Mechanics". In Encyclopedic Dictionary of Polymers, 324. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_5270.
Testo completoAtti di convegni sul tema "Fracture mechanics"
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Backers, T., e O. Stephansson. "Fracture Mechanics - Fracture Toughness Determination". In 70th EAGE Conference and Exhibition - Workshops and Fieldtrips. European Association of Geoscientists & Engineers, 2008. http://dx.doi.org/10.3997/2214-4609.20147956.
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McLean, M. L., D. N. Espinoza e B. Ahmmed. "Evolution of Hydraulic Fracture Permeability in EGS Considering Natural Fracture Compressibility and Strength of the Surrounding Rock". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0853.
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ABSTRACT: The long-term success of an Enhanced Geothermal System (EGS) project requires distributed fluid flow in created fractures, ideally each with uniform and moderate permeability to avoid early thermal breakthrough. Yet, thermal depletion causes fracture opening, increasing the likelihood of flow channeling in areas with high fracture permeability. Furthermore, the effective reservoir rock stiffness (including natural fracture compliance) has a first-order impact on thermally induced stress changes, and thus fracture permeability. The objective of this work is to explore the role of thermal depletion on hydraulic fracture permeability considering a non-linear elastoplastic geothermal reservoir response. We utilize three-dimensional numerical simulations based on effective medium theory of fractured rocks to implicitly account for natural fracture compressibility and strength. Results demonstrate that a portion of the thermal strain-induced by cooling- is absorbed by natural fracture compressibility, which reduces the overall stress change, and tends to attenuate hydraulic fracture opening. Critically stressed natural fractures can yield during operation and decrease the likelihood of flow channeling. Lastly, the modeling results indicate that linear elastic models tend to overpredict fracture opening compared to models that account for effective properties of fractured rock masses. 1 INTRODUCTION Predictions of recoverable heat energy from Enhanced Geothermal Systems (EGS) reservoirs with models that neglect stress-dependent and non-linear fracture permeability are conservative estimates (Kohl et al., 1995). Flow channeling and thermal short-circuiting caused by thermo-poroelastic coupled feedback is often observed early on in field tests and would limit the installed capacity unless efforts were made to improve the flow distribution (MIT, 2006). Localized fracture opening increases injectivity and decreases the geothermal effective reservoir volume by localizing injected flow (Hicks et al., 1996). Hence, reservoir stresses (in-situ and any changes during operation) play a significant role in the distribution of EGS circulation fluid and evolution of fracture permeability (McLean and Espinoza, 2023). Spatial heterogeneity in the initial fracture aperture may further decrease reservoir performance from the beginning because preferential flow paths may exist prior to injection (Guo et al., 2016).
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He, Yongsheng, Xuanhe Tang, Haiyan Zhu, Kuidong Li, Wei Liu, Feng Zheng, Jialin Xiao e Yuan You. "Research on Productivity Recovery Mechanism of Fractured Parent Well of Interwell Stereodimensional Infill Well in Fuling Shale Gas Reservoir, Sichuan Basin". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0432.
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ABSTRACT During the fracturing process of infill wells in the Fuling shale gas reservoir, it was found through real-time monitoring of fracturing that the monitored pressure of the parent well increased to different degrees when each fractured stage of the adjacent infill wells was fractured, and a significant increase in production following the re-opening of the well. To study the production and pressure recovery mechanisms of parent well associated with the infill well fracturing, a coupled flow and geomechanics model was established based on the comprehensive work flow of four-dimensional in-situ stress during the devolopement of multi-layer three-dimensional infill horizontal well in shale gas reservoir. In the integrated modeling, a natural fractures network was embedded in the geological model firstly. Second, a fracturing model is developed to simulate hydraulic fracture propagation of parent wells. Thirdly, a coupling flow and geomechanics model was established to simulate the spatiotemporal stress evolution in a multilayer shale gas reservoir with complex fracture geometry. Finally, the complex hydraulic fractures propagation of the infill well was stimulated. It can be concluded from the simulation results that: (1) Reservoir stress changes are influenced by fracture modification, but the range of stress evolution is greater than the range of fracture modification; (2) The natural fracture zone connects the fractured wells to the producing wells, and the fluid can be run long distances through the natural fracture zone to the fracture modification edge of the old wells to achieve the fracturing of more wells and to increase the production of the old wells (3) The fractures(tennsile fractures, shear fractures) communicating between the fractured edges of the tightened wells and the old wells are able to transfer fracturing fluids and add production to the old wells. This discovery is beneficial to the production of fractured encrypted wells and the continued high production of old wells.
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Mei, Z., W. Li, W. Jin, G. Neupane e T. Atkinson. "Fluid Flow in a Fracture Network Under Changing Stresses: A Laboratory Study". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0170.
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ABSTRACT: Fluid flow in fractured rocks is ubiquitous in natural and human-induced subsurface processes. Subsurface technologies, such as in-situ mining, CO2 storage and geothermal exploitations, require large contact areas between the flowing fluid and the rock to facilitate efficient heat and mass transport and, therefore, ensure the effectiveness of these technologies. Much of the experimental research on fluid flow in fractures has focused on a single fractures in a rock specimen, which leaves the fluid flow in fracture networks under changing stresses largely unexplored. Here, we study fluid flow in a fracture network under changing stresses using a triaxial system. We create the fracture network composed of five orthogonal fractures in rock specimens by assembling six saw-cut rock parts. We measure the overall permeability of the fracture networks under changing vertical and horizontal stresses. We find that the fracture network permeability decreases when the vertical and horizontal stresses both increase. A greater reduction of permeability is observed with increasing horizontal stress than that with increasing vertical stress. We show that this phenomenon results from the larger total area of the vertical fractures than that of the horizontal fractures, making the fracture network more sensitive to horizontal stress changes. Our study shows the importance of the relative orientations between the fractures and the stresses in determining the permeability of the fracture network. This insight can be incorporated to improve the discrete and continuum modeling of fracture networks. 1 INTRODUCTION Fracture networks are the "highways" for the fluid flow in subsurface rock-fluid systems. They provide a fast path for contaminant transport in fractured aquifers (Tsang and Tsang, 1987; Grisak and Pickens, 1980; Grisak et al., 1980). They could increase the permeability of a geothermal reservoir and, at the same time, reduce the heat extraction efficiency by inducing short-circuiting (Gee et al., 2021). They can also localize the dissolution of porous rocks to the fracture along and induce larger cavities earlier (Li et al., 2021). The overall permeability of a fracture network is affected by the fracture orientation, stress conditions, and fluid pressure. Understanding and predicting the the fracture network permeability as the stresses and pore pressure changes are important for many engineering applications in the subsurface rock-fluid systems.
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Cao, Meng, e Mukul M. Sharma. "Creation of a Data-Calibrated Discrete Fracture Network of the Utah FORGE Site". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0822.
Testo completoAbstract (sommario):
ABSTRACT Three single-cluster hydraulic fracture stages were pumped at the Frontier Observatory for Research in Geothermal Energy (FORGE) site in Milford, Utah. Our goal was to develop a robust model to accurately represent the formation of fracture networks in this naturally fractured geothermal reservoir. To begin this process, we used geological and geophysical data and data from one-dimensional Fullbore Formation MicroImager (FMI) to build a discrete fracture network model for the natural fractures. The natural fracture network (DFN) was built stochastically with areal density, length, and orientation distribution of natural fractures. We then took one-dimensional synthetic cores to ensure that the number and density of fractures per unit length of the core matched with the actual measurements (for each fracture set) until the best statistical description of natural fractures was found. The length distribution of natural fractures was simulated using a power law distribution. INTRODUCTION Utah Frontier Observatory for Research in Geothermal Energy (FORGE) is a dedicated laboratory for developing, testing, and accelerating breakthroughs in EGS technologies to advance the use of geothermal resources (Department of Energy, 2022). Natural fractures have been indicated by outcrop data and Fullbore Formation MicroImager (FMI) log data. Most of the data can be found directly or indirectly in the Geothermal Data Repository (GDR), which includes data from Utah FORGE, as well as all data collected from other researchers funded by the Geothermal Technologies Office (GTO) (Department of Energy, 2022). Fig. 1 shows the locations of the vertical pilot well (58-32), the highly deviated injection well (16A(78)-32), and another deep vertical well (56-32). In this paper, based on the data provided by these wells, a discrete fracture network (DFN) was developed to characterize the natural fracture network. Fractures are explicitly expressed in the form of planes of weakness. A DFN realization (Fig. 2) is built with a specified distribution of fracture orientation, length, and density (Cao et al., 2023). A model that can simulate fracture propagation in naturally fractured reservoirs can be found in Cao and Sharma (2023, 2022a, 2022b).
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Urbancic, T. I., e S. C. Maxwell. "Microseismic Imaging of Fracture Behavior in Naturally Fractured Reservoirs". In SPE/ISRM Rock Mechanics Conference. Society of Petroleum Engineers, 2002. http://dx.doi.org/10.2118/78229-ms.
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Liu, Xiongwei, Bing Zhao, Zikang Wang, Yaoyao Sun, Xiaoguang Wu, Xu Zhang e Wenchao Zou. "Numerical Simulation on Fracture Propagation Behaviors in Grid-like Fractured Carbonate Reservoirs in Shunbei". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0888.
Testo completoAbstract (sommario):
ABSTRACT: The carbonate formations are characterized by developing continuous grid-like fractured structures, which pose a great challenge on effective hydraulic fracturing. In order to investigate the fracture propagation behavior in such grid-like fracture carbonate reservoirs and the interaction between hydraulic fracture and grid-like fracture, we employed a Unconventional Fracture Model (UFM) based on the boundary element approach in this paper to simulate the fracturing process in fractured carbonate reservoirs. The effects of key geological and engineering parameters such as fracture approach angle, pump displacement, and stress difference on stimulated reservoir volume were analyzed, and well trajectories were also optimized. Under the condition of Shunbei carbonate reservoir, when the angle α between the grid-like fracture and the horizontal well is 90°, the hydraulic fracture tends to extend parallel to the direction of the grid-like fracture, when α is 45°, the hydraulic fracture tends to penetrate the grid-like fracture and then propagate along the maximum principal stress, and when α is less than 45°, the hydraulic fracture tends to penetrate the grid-like fracture and then be captured by the natural fracture. In the Shunbei reservoirs, with a local stress difference of 40 MPa, the optimal pump displacement is 4∼6 m3/min. 1. INTRODUCITON Marine carbonate reservoirs are rich for oil and gas resources. In world's proven oil and gas reserves, 60% in the marine carbonate reservoirs, that has become a key area of oil and gas exploitation. Among the marine carbonate reservoirs, grid-like fractured reservoirs is a special structure. Marine carbonate reservoirs are stretched and shear by geological processes, forming deep faults and grid-like fractured zones, that are grid-like fractured reservoirs. Which generally exist in ultra-deep, high-temperature and high-pressure geologic environments, and have received focused attention in recent years (Wang W et al., 2023; LI Y et al., 2022). Currently, hydraulic fracturing is the main means for exploiting grid-like fracture reservoirs. However, hydraulic fracturing communication large grid-like fractures and many natural fractures has limited, and the classical theory of fracture propagation is not applicable (Hui G et al., 2023). Therefore, to study the propagation law of hydraulic fracture in grid-like fracture reservoirs is important. So far, many scholars have conducted a lot of research on the interaction between hydraulic fracture and grid-like fracture (Zhang Q et al., 2021). However, fracture propagation in grid-like fracture Still have not theoretical support, and the mechanism of hydraulic fracture propagation in grid-like fractured reservoirs is not clear. Based on the UFM model and with the help of Kinetix (Kresse O et al., 2013), which is an integrated software platform for geo-engineering. The authors modeled the grid-like fractured reservoirs, and studied the propagation of hydraulic fracture under the condition of grid-like fracture medium (Ma D C et al., 2023).
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Luo, Pandeng, Chunyue Li, Yaoyao Sun, Zhongwei Huang, Xiaoguang Wu, Xu Zhang, Ruiyue Yang e Zikang Wang. "Laboratory Study of Fracture Propagation Behaviors in Fractured-Cavity Carbonate Reservoirs in Shunbei Oilfield". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0884.
Testo completoAbstract (sommario):
ABSTRACT: In order to determine the interaction behaviors between artificial fracture and nature fracture-cavity, we performed a laboratory true tri-axial fracturing experiment on natural carbonate outcrops with Mico-fracture and pores, and the natural fracture-cavity are simulated by pre-existing fracture-cavity. The propagation of artificial fractures is investigated by changing the approach angle for fracture and maximum horizontal stress, and arrangement of pre-existing cavity. Moreover, re-injection experiments are used to evaluate the conductivity of fractures. The results indicate that the extension of fractures in pre-existing fractured-cavity carbonate rocks is random. The extension of artificial fracture is steering when it encounters pre-existing cavity. Three interaction modes occur between artificial fracture and pre-existing fracture, and the large approach angle allows the artificial fracture to pass through the pre-existing fracture. Artificial fracture is always captured by pre-existing fracture, and the tortuosity is greater in the process of propagation. The breakdown pressure of pre-existing fracture-cavity carbonate rocks is about 50% lower compared to that of tight carbonate rock. Pre-existing fracture-cavity make the conductivity greater of effective fracture, but the length of effective fracture is not conducive to the conductivity. This research may contribute to the field application of hydraulic fracturing in carbonate formation. 1. INTRODUCTION The increase of burial depth causes the gradual decrease of carbonate porosity, which is a past view on the lack of high-quality reservoirs in deep carbonate rocks (SCHMOKER J W et al., 1982; EHRENBERG S N et al., 2009). In recent years, 60 % of the world ‘s new oil and gas reserves come from deep strata, and the exploration potential is huge (Wei C et al., 2017; Sun K et al., 2022). The deep strata of oil and gas reserves and production of marine carbonate rocks in Tarim Basin, Sichuan Basin and Ordos Basin have been increasing rapidly year by year, which has attracted wide attention from the industry. In the proven deep strata of carbonate reservoirs, two-thirds belonging to the type of fractured-cavity reservoirs (Guo W et al., 2022). Complex spatial structure is the characteristic of fractured-cavity reservoir, mainly including matrix pores, karst cavity, and natural fractures with different development degrees (Durrani M Z A et al., 2021; Tian F et al.,2019; Sun, K et al., 2021). Due to the extreme heterogeneity and complex flow environment of facture-cavity carbonate formation, that is a challenge to increase oil and gas extraction rate (Tian F et al.,2016; Dmitriy A. Martyushev et al., 2022).
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Han, Yanhui, Bo Luo, Frank Chang e Wenwen Li. "Numerical Investigation of Particle Bridging near Fracture Entrance". In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-2022.
Testo completoAbstract (sommario):
ABSTRACT: Particle transport and bridging inside fractures is an important subject in wellbore drilling and completion. For example, when drilling naturally fractured formations, depleted formations, and offshore formations where fractures can be easily induced or reactivated, loss circulation material (LCM) containing high loading of solid particles is commonly used to seal the pre-existing or newly created fractures to prevent mud loss. The particles are expected to bridge the fracture at the entrance area to maximize the sealing effectiveness and efficiency. A different example is the well completion with hydraulic fracturing, in which the proppant particles are injected with fracturing fluids to keep the fractures open after the fracturing pressure is released. To maximize the opening area of the fractures thus the well productivity, the placement of the proppant particles is expected to reach the far region of the fractures, so the particle bridging near the fracture entrance should be avoided. On the other hand, should the objective be promoting multiple fractures, particle bridging against a pre-existing or dominant fracture is beneficial to redirect the fracturing fluid into less conductive fractures. The ability to predict the bridging location and time with given solid particle size and concentration, fluid viscosity and operating parameters will help design drilling fluid, LCM, fracturing fluid, and diverting materials. In this work, a simulator is developed for numerically experimenting the particle bridging in the entrance area of a fracture. The fluid flow in the fracture is simulated by pipe network flow model. The equation of particle advection with fluid is solved using the upwind numerical scheme. The particle bridging is evaluated using a blocking criterion proposed in the literature. After all the implemented computational components are tested and verified, extensive parametric studies are then performed to experiment how various parameters, including particle size and concentration, fluid viscosity and injection rate, influence the particle bridging location and time near the entrance area. Accordingly, a few recommendations are provided to assist the design and selection of diverting and LCM agents.
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POWERS, E., N. ELFER e C. CASADABAN. "Fracture mechanics expert system". In 30th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-876.
Testo completoRapporti di organizzazioni sul tema "Fracture mechanics"
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Robertson, Brett Anthony. Phase Field Fracture Mechanics. Office of Scientific and Technical Information (OSTI), novembre 2015. http://dx.doi.org/10.2172/1227184.
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Bass, B. R. (Fracture mechanics of inhomogeneous materials). Office of Scientific and Technical Information (OSTI), ottobre 1990. http://dx.doi.org/10.2172/6548880.
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Sinclair, G. B. Fundamentals of Fatigue and Fracture Mechanics. Fort Belvoir, VA: Defense Technical Information Center, ottobre 1988. http://dx.doi.org/10.21236/ada201435.
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Annigeri, B. S. Fracture Mechanics Analysis for Short Cracks. Fort Belvoir, VA: Defense Technical Information Center, agosto 1987. http://dx.doi.org/10.21236/ada192002.
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Cheverton, R. D., e T. L. Dickson. HFIR vessel probabilistic fracture mechanics analysis. Office of Scientific and Technical Information (OSTI), gennaio 1997. http://dx.doi.org/10.2172/654200.
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Cowles, B. A., A. B. Thakker e G. E. King. Fracture Mechanics of Multiple Crack Initiations. An Application for Fracture Mechanics Analysis of Gas Turbine Engine Disks. Fort Belvoir, VA: Defense Technical Information Center, ottobre 1985. http://dx.doi.org/10.21236/ada162998.
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Popelar, C. H., J. D. Walker, C. E. Anderson, Johnson Jr., Beissel G. R. e S. R. Penetrator Case Fracture Predictive Technoiogy: Volume 1-Dynamic Fracture Mechanics Methodology. Fort Belvoir, VA: Defense Technical Information Center, giugno 1999. http://dx.doi.org/10.21236/ada367712.
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Swartz, Stuart E. Applicability of Fracture Mechanics Methodology to Cracking and Fracture of Concrete. Fort Belvoir, VA: Defense Technical Information Center, febbraio 1986. http://dx.doi.org/10.21236/ada165639.
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Liu, C. T. Fracture Mechanics and Service Life Prediction Research. Fort Belvoir, VA: Defense Technical Information Center, settembre 1999. http://dx.doi.org/10.21236/ada409488.
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Mason, J. J. Application of Dynamic Fracture Mechanics to Composites. Fort Belvoir, VA: Defense Technical Information Center, giugno 1998. http://dx.doi.org/10.21236/ada351990.
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