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1
Schoenberg, Michael, e Colin M. Sayers. "Seismic anisotropy of fractured rock". GEOPHYSICS 60, n. 1 (gennaio 1995): 204–11. http://dx.doi.org/10.1190/1.1443748.
Testo completoAbstract (sommario):
A simple method for including the effects of geologically realistic fractures on the seismic propagation through fractured rocks can be obtained by writing the effective compliance tensor of the fractured rock as the sum of the compliance tensor of the unfractured background rock and the compliance tensors for each set of parallel fractures or aligned fractures. The compliance tensor of each fracture set is derivable from a second rank fracture compliance tensor. For a rotationally symmetric set of fractures, the fracture compliance tensor depends on only two fracture compliances, one controlling fracture compliance normal, the other, tangential, to the plane of the fractures. The stiffness tensor, which is more useful in the consideration of elastic wave propagation through rocks, can then be obtained by inversion. The components of the excess fracture compliance tensor represent the maximum amount of information that can be obtained from seismic data. If the background rock is isotropic and the normal and shear compliance of each fracture are equal, although different from those of other fractures, the effective elastic behavior of the fractured rock is orthorhombic for any orientation distribution of fractures. A comparison of the theory with recent ultrasonic experiments on a simulated fractured medium shows near equality of the normal and shear compliance for the case of air‐filled fractures.
2
Wang, Yueying, Jun Yao, Shuaishi Fu, Aimin Lv, Zhixue Sun e Kelvin Bongole. "Simulation of counter-current imbibition in water-wet fractured reservoirs based on discrete-fracture model". Open Physics 15, n. 1 (3 agosto 2017): 536–43. http://dx.doi.org/10.1515/phys-2017-0061.
Testo completoAbstract (sommario):
AbstractIsolated fractures usually exist in fractured media systems, where the capillary pressure in the fracture is lower than that of the matrix, causing the discrepancy in oil recoveries between fractured and non-fractured porous media. Experiments, analytical solutions and conventional simulation methods based on the continuum model approach are incompetent or insufficient in describing media containing isolated fractures. In this paper, the simulation of the counter-current imbibition in fractured media is based on the discrete-fracture model (DFM). The interlocking or arrangement of matrix and fracture system within the model resembles the traditional discrete fracture network model and the hybrid-mixed-finite-element method is employed to solve the associated equations. The Behbahani experimental data validates our simulation solution for consistency. The simulation results of the fractured media show that the isolated-fractures affect the imbibition in the matrix block. Moreover, the isolated fracture parameters such as fracture length and fracture location influence the trend of the recovery curves. Thus, the counter-current imbibition behavior of media with isolated fractures can be predicted using this method based on the discrete-fracture model.
3
Zhang, Qinghe, Bing Zhang, Chen Chen, Ling Li, Xiaorui Wang, Bowen Jiang e Tianle Zheng. "A Test Method for Finding Early Dynamic Fracture of Rock: Using DIC and YOLOv5". Sensors 22, n. 17 (23 agosto 2022): 6320. http://dx.doi.org/10.3390/s22176320.
Testo completoAbstract (sommario):
Intelligent monitoring and early warning of rock mass failure is vital. To realize the early intelligent identification of dynamic fractures in the failure process of complex fractured rocks, 3D printing of the fracture network model was used to produce rock-like specimens containing 20 random joints. An algorithm for the early intelligent identification of dynamic fractures was proposed based on the YOLOv5 deep learning network model and DIC cloud. The results demonstrate an important relationship between the overall strength of the specimen with complex fractures and dynamic fracture propagation, and the overall specimen strength can be judged semi-quantitatively by counting dynamic fracture propagation. Before the initiation of each primary fracture, a strain concentration area appears, which indicates new fracture initiation. The dynamic evolution of primary fractures can be divided into four types: primary fractures, stress concentration areas, new fractures, and cross fractures. The cross fractures have the greatest impact on the overall strength of the specimen. The overall identification accuracy of the four types of fractures identified by the algorithm reached 88%, which shows that the method is fast, accurate, and effective for fracture identification and location, and classification of complex fractured rock masses.
4
Alemi, Dr Mehrdad, e Hossein Jalalifar. "Advanced Concepts in Naturally Fractured Reservoirs with Analysis of Field Data". Indian Journal of Petroleum Engineering 2, n. 1 (30 maggio 2022): 1–5. http://dx.doi.org/10.54105/ijpe.b1912.052122.
Testo completoAbstract (sommario):
Dual porosity reservoir is mainly defined as fractured reservoir. The Two porosities are included for fracture and matrix, Flow in the fractures, oil storage in the matrix. Dual Permeability reservoir are those pay zones with flow in both the fracture and matrix systems. Single porosity means matrix, dual porosity means both matrix and fractures and triple porosity means matrix, fractures and vugs. The description of displacement mechanisms in fractured reservoirs can be construed as: oil expansion, gravity forces, capillary forces, balance of gravity and capillary forces, diffusion and convection. Fractures are usually found in limestone and dolomites due to solution, re-crystallization. Two categories of fractures are available such as: Open Fractures and Closed Fractures which depend mainly on circulation water and precipitation. Fractures which are closed at surface conditions may be open in reservoir conditions. Fractures related to folding axis are such as: longitudinal fractures, along the folding axis and transverse fractures, perpendicular to the folding axis and diagonal fractures, in relation with the folding axis. There are some pivotal issues and expressions in fractured reservoirs that in this paper, an approach to the advanced concepts in Naturally Fractured Reservoirs has been studied.
5
Guo, Jingjing, Haitao Wang, Liehui Zhang e Chengyong Li. "Pressure Transient Analysis and Flux Distribution for Multistage Fractured Horizontal Wells in Triple-Porosity Reservoir Media with Consideration of Stress-Sensitivity Effect". Journal of Chemistry 2015 (2015): 1–16. http://dx.doi.org/10.1155/2015/212901.
Testo completoAbstract (sommario):
Triple-porosity model is usually adopted to describe reservoirs with multiscaled pore spaces, including matrix pores, natural fractures, and vugs. Multiple fractures created by hydraulic fracturing can effectively improve the connectivity between existing natural fractures and thus increase well deliverability. However, little work has been done on pressure transient behavior of multistage fractured horizontal wells in triple-porosity reservoirs. Based on source/sink function method, this paper presents a triple-porosity model to investigate the transient pressure dynamics and flux distribution for multistage fractured horizontal wells in fractured-vuggy reservoirs with consideration of stress-dependent natural fracture permeability. The model is semianalytically solved by discretizing hydraulic fractures and Pedrosa’s transformation, perturbation theory, and integration transformation method. Type curves of transient pressure dynamics are generated, and flux distribution among hydraulic fractures for a fractured horizontal well with constant production rate is also discussed. Parametric study shows that major influential parameters on transient pressure responses are parameters pertinent to reservoir properties, interporosity mass transfer, and hydraulic fractures. Analysis of flux distribution indicates that flux density gradually increases from the horizontal wellbore to fracture tips, and the flux contribution of outermost fractures is higher than that of inner fractures. The model can also be extended to optimize hydraulic fracture parameters.
6
Kuchuk, Fikri, e Denis Biryukov. "Pressure-Transient Tests and Flow Regimes in Fractured Reservoirs". SPE Reservoir Evaluation & Engineering 18, n. 02 (31 marzo 2015): 187–204. http://dx.doi.org/10.2118/166296-pa.
Testo completoAbstract (sommario):
Summary Fractures are common features in many well-known reservoirs. Naturally fractured reservoirs include fractured igneous, metamorphic, and sedimentary rocks (matrix). Faults in many naturally fractured carbonate reservoirs often have high-permeability zones, and are connected to numerous fractures that have varying conductivities. Furthermore, in many naturally fractured reservoirs, faults and fractures can be discrete (rather than connected-network dual-porosity systems). In this paper, we investigate the pressure-transient behavior of continuously and discretely naturally fractured reservoirs with semianalytical solutions. These fractured reservoirs can contain periodically or arbitrarily distributed finite- and/or infinite-conductivity fractures with different lengths and orientations. Unlike the single-derivative shape of the Warren and Root (1963) model, fractured reservoirs exhibit diverse pressure behaviors as well as more than 10 flow regimes. There are seven important factors that dominate the pressure-transient test as well as flow-regime behaviors of fractured reservoirs: (1) fractures intersect the wellbore parallel to its axis, with a dipping angle of 90° (vertical fractures), including hydraulic fractures; (2) fractures intersect the wellbore with dipping angles from 0° to less than 90°; (3) fractures are in the vicinity of the wellbore; (4) fractures have extremely high or low fracture and fault conductivities; (5) fractures have various sizes and distributions; (6) fractures have high and low matrix block permeabilities; and (7) fractures are damaged (skin zone) as a result of drilling and completion operations and fluids. All flow regimes associated with these factors are shown for a number of continuously and discretely fractured reservoirs with different well and fracture configurations. For a few cases, these flow regimes were compared with those from the field data. We performed history matching of the pressure-transient data generated from our discretely and continuously fractured reservoir models with the Warren and Root (1963) dual-porosity-type models, and it is shown that they yield incorrect reservoir parameters.
7
Zhao, Kai, Runsen Li, Haoran Lei, Wei Gao, Zhenwei Zhang, Xiaoyun Wang e Le Qu. "Numerical Simulation of Influencing Factors of Hydraulic Fracture Network Development in Reservoirs with Pre-Existing Fractures". Processes 10, n. 4 (15 aprile 2022): 773. http://dx.doi.org/10.3390/pr10040773.
Testo completoAbstract (sommario):
The intersection behavior of hydraulic fractures and single natural fractures has been studied in detail; however, in fractured reservoirs, natural fractures are numerous and interlaced and the intersection of hydraulic fractures and multiple natural fractures occurs during the fracturing process. This intersection behavior is more complex and there is a lack of research on this topic at present. In this study, a numerical simulation model of the interaction between hydraulic fractures and a series of natural fractures was established, the main factors that affect the formation scale of a fracture network during the hydraulic fracturing of a fractured reservoir were studied using the numerical simulation method, and the parameters were also studied. The results showed that the natural fracture trend, in situ stress difference, and injection flow rate have an impact on the scale of a fracture network. The larger the in situ stress difference, the smaller the scale of the fracture network, which gradually changes from multiple clusters of fractures to single fractures. The larger the injection flow rate, the larger the scale of the fracture network. In the uniform stress field, the direction of a natural fracture is closer to the direction of principal stress, so the lower the fracture extension pressure, the smaller the scale of the network. On the contrary, the farther away from the principal stress direction, the lower the fracture extension pressure and the higher the extension pressure, the larger the scale of the fracture network.
8
Zhang, Peng, Yaniv Brick e Mukul M. Sharma. "Numerical study of an electrode-based resistivity tool for fracture diagnostics in steel-cased wellbores". GEOPHYSICS 83, n. 2 (1 marzo 2018): D41—D48. http://dx.doi.org/10.1190/geo2017-0355.1.
Testo completoAbstract (sommario):
The efficiency of a hydraulic fracture treatment depends primarily on the dimensions and orientation of propped fractures. We have developed a novel electrode-based resistivity tool concept for mapping proppant distribution in hydraulic fractures in steel-cased wellbores. The proposed tool configuration is shown to overcome the severe limitations of induction tools for the detection and resolution of propped fracture geometries in such wellbores. The concept makes use of an array of electrically insulating gap subsections, which are installed and cemented as permanent parts of the casing string, separating the casing sections. By imposing voltages on the insulating gaps, the conductive casing is excited directly, thus avoiding through-casing signal degradation caused by its high electrical conductivity. This allows us to detect subsurface fractures propped with conductive proppant. The envisioned measurements are performed by running a bottom-hole assembly into the fractured zone on a coiled tubing to impose a voltage across each insulating gap at a time, before and after hydraulic fracture operations. For each excited insulating gap, the voltages across all other insulating gaps are recorded by the electronics embedded in the insulating gaps. To interpret the envisioned measurements, a forward model of the tool, based on a finite volume method, is developed, and the design’s sensitivity to the fracture parameters is demonstrated via case studies. The results indicate that measurements made based on the proposed concept will be highly sensitive to a fracture’s location, size, and angle, and less sensitive to a fracture’s shape. Simulations also indicate that direct contact of the fracture with an excited casing section enables the differentiation of fractures of up to a 100 m radius. Fractures with angles greater than 30° or aspect ratios greater than two can also be distinguished from the ones orthogonal to the well or with an aspect ratio of one.
9
Feng, Yueli, Yuetian Liu e Gang Lei. "Study on Stress-Dependent Permeability of Fracture Networks in Fractured Porous Media". Geofluids 2021 (24 giugno 2021): 1–19. http://dx.doi.org/10.1155/2021/7433547.
Testo completoAbstract (sommario):
In order to investigate the stress-sensitive characteristics of fracture networks under reservoir actual stress condition and its influence on the seepage in fractured porous media, we carried out permeability tests on experimental models with fracture networks under constant-volume boundary condition. In addition, a novel analytical stress-dependent permeability model of fracture networks in different directions was derived. Based on the test results and the proposed analytical model, the effects of various parameters (e.g., initial fracture aperture, fluid pressure, rock elastic modulus, effective-stress coefficient, and fracture dip) on deformation characteristics of fracture networks and the corresponding permeability tensor of fracture networks were studied. The research results show that, for a fractured porous media with a single group of fractures, the principal value of permeability is always parallel to the fracture-development direction. With increasing effective stress, the principal value of permeability decreases; however, the principal value direction remains unchanged. Moreover, for the fractured porous media with multiple sets of fractures, the principal direction of equivalent permeability will be inclined to the fractures with larger fracture aperture. Specifically, for the fractured porous media with two sets of intersecting fractures, the principal direction of equivalent permeability is parallel to the angular bisector of these two sets of intersecting fractures. Furthermore, the greater the difference of the fracture aperture change rate under effective stress, the more obvious the deviation of the permeability principal direction. The derived analytical model is of great theoretical and scientific significance to deepen the understanding of the stress-sensitive permeability of fractured reservoirs.
10
Shi, Shanzhi, Renyan Zhuo, Leiming Cheng, Yuankai Xiang, Xinfang Ma e Tao Wang. "Fracture Characteristics and Distribution in Slant Core from Conglomerate Hydraulic Fracturing Test Site (CHFTS) in Junggar Basin, Northwest China". Processes 10, n. 8 (19 agosto 2022): 1646. http://dx.doi.org/10.3390/pr10081646.
Testo completoAbstract (sommario):
Hydraulic fracture networks, especially fracture geometry, height growth, and proppant transport within the networks, present a critical influence on productivity evaluation and optimization of fracturing parameters. However, information about hydraulic fracture networks in post-fractured formations is seldom available. In this study, the characteristics (density and orientation) of hydraulic fractures were obtained from field observations of cores taken from conglomerate hydraulic fracturing test site (CHFTS). A large number of fractures were observed in the cores, and systematic fracture description was carried out. The fracture analysis data obtained includes fracture density, fracture depth, fracture orientation, morphology, fracture surface features, apertures, fill, fracture mechanical origin (type), etc. Our results show that 228 hydraulic fractures were intersected in a span of 293.71 m of slant core and composed of irregularly spaced single fractures and fracture swarms. One of the potential sources of the observed fracture swarms is near-wellbore tortuosity. Moreover, for regions far away from the wellbore, reservoir heterogeneity can promote complex hydraulic fracture trajectories. The hydraulic fractures were mainly cross-gravel and high-angle fractures and align with maximum horizontal stress (SHmax) ± 15°. The fracture density, orientations, and types obtained from the core fracture description provided valuable information regarding fracture growth behavior. For the near-wellbore area with a transverse distance of less than 25 m from the hydraulically-fractured wellbore, tensile fractures were dominant. While for the area far away from the wellbore, shear fractures were dominant. Our results provide improved understanding of the spatial hydraulic fracture dimensions, proppant distribution, and mechanism of hydraulic fracture formation. The dataset acquired can also be used to calibrate numerical models and characterize hydraulic fracture geometry and proppant distribution.
11
Fumagalli, Alessio, e Eirik Keilegavlen. "Dual Virtual Element Methods for Discrete Fracture Matrix models". Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 74 (2019): 41. http://dx.doi.org/10.2516/ogst/2019008.
Testo completoAbstract (sommario):
The accurate description of fluid flow and transport in fractured porous media is of paramount importance to capture the macroscopic behavior of an oil reservoir, a geothermal system, or a CO2 sequestration site, to name few applications. The construction of accurate simulation models for flow in fractures is challenging due to the high ratio between a fracture’s length and width. In this paper, we present a mixed-dimensional Darcy problem which can represent the pressure and Darcy velocity in all the dimensions, i.e. in the rock matrix, in the fractures, and in their intersections. Moreover, we present a mixed-dimensional transport problem which, given the Darcy velocity, describes advection of a passive scalar into the fractured porous media. The approach can handle both conducting and blocking fractures. Our computational grids are created by coarsening of simplex tessellations that conform to the fracture’s surfaces. A suitable choice of the discrete approximation of the previous model, by virtual finite element and finite volume methods, allows us to simulate complex problems with a good balance of accuracy and computational cost. We illustrate the performance of our method by comparing to benchmark studies for two-dimensional fractured porous media, as well as a complex three-dimensional fracture geometry.
12
Gray, Sarah N., Mathieu Spriet, Tanya C. Garcia, Francisco A. Uzal e Susan M. Stover. "Preexisting lesions associated with complete diaphyseal fractures of the third metacarpal bone in 12 Thoroughbred racehorses". Journal of Veterinary Diagnostic Investigation 29, n. 4 (19 aprile 2017): 437–41. http://dx.doi.org/10.1177/1040638717704866.
Testo completoAbstract (sommario):
We characterized features of complete diaphyseal fractures of third metacarpal bones in Thoroughbred racehorses. Given that stress fractures are known to occur in the third metacarpal bone, an additional aim was to determine if complete fractures are associated with signs of a preexisting incomplete stress fracture. Bilateral metacarpi from 12 Thoroughbred racehorses euthanized because of complete unilateral metacarpal diaphyseal fracture were examined visually and radiographically. Open, comminuted, transverse or short oblique fractures occurred in the middle of the diaphysis or supracondylar region. Periosteal surface discoloration and bone callus formation contiguous with the fracture line were present in fractured bones. All contralateral intact metacarpi had gross anatomic lesions, and 10 had radiographic abnormalities similar to those observed on fractured metacarpi. Catastrophic metacarpal fractures occurred in racehorses with bilateral evidence of preexisting bone injury.
13
Jiang, Le, Peng Gao, Jie Liu, Yunbin Xiong, Jing Jiang, Ruizhong Jia, Zhongchao Li e Pengcheng Liu. "Simulation and Optimization of Dynamic Fracture Parameters for an Inverted Square Nine-Spot Well Pattern in Tight Fractured Oil Reservoirs". Geofluids 2020 (22 settembre 2020): 1–9. http://dx.doi.org/10.1155/2020/8883803.
Testo completoAbstract (sommario):
Dynamic fractures are a geological attribute of water flooding development in tight fractured oil reservoirs. However, previous studies have mainly focused on the opening mechanism of dynamic fractures and the influence of dynamic fractures on development. Few attempts have been made to investigate the optimization of the dynamic fracture parameter. In this study, the inverted square nine-spot well pattern model is established by taking fractured reservoir’s heterogeneity and its threshold pressure gradients into account. This simulation model optimizes the various parameters in a tight fractured oil reservoir with dynamic fractures, that is, the intersection angle between the dynamic fractures and the well array, the number of dynamic fractures, the penetration ratio, and the conductivity of the oil well’s hydraulic fractures. The results of this optimization are used to investigate the oil displacement mechanism of dynamic fractures and to discuss a mechanism to enhance oil recovery using an inverted square nine-spot well pattern. The simulation results indicate that a 45° intersection angle can effectively restrain the increase in the water cut. A single dynamic fracture can effectively control the displacement direction of the injected water and improve the oil displacement efficiency. Moreover, the optimal penetration ratio and the conductivity of the hydraulic fracture are 0.6 and 40 D-cm, respectively.
14
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.
15
Al Nefaie, Hamed, Zuhair Alsuhaymi, Ahmed Alzahrani, Abdulaziz Alghamdi, Emtenan Esmael, Nuran Eid, Eyad Agheel et al. "Fracture Patterns in Saudi Arabian Road Traffic Accidents Over the Last 12 Years: A Systematic Review". Journal of Healthcare Sciences 02, n. 11 (2022): 413–21. http://dx.doi.org/10.52533/johs.2022.21113.
Testo completoAbstract (sommario):
Background: Road traffic accidents are a major non-communicable epidemic that accounts for death and morbidity in the world today. Despite considerable attention given to health statistics of road traffic accidents (RTAs), the pattern of bone fracture aspects of injuries resulting from RTAs is not fully understood in Saudi Arabia. This review aimed to study the epidemiological pattern of fractures due to RTAs in Saudi Arabia. Methods: This systematic review was based on the latest evidence of RTA fractures in the Kingdom of Saudi Arabia (SAUDI ARABIA). All articles published during the last 12 years on road traffic accident-associated fractures in SAUDI ARABIA were analyzed. We examined 12 studies published between 2012 and 2022. Eleven included studies were cross-sectional studies and collected data retrospectively, while one study was a cohort. Results: A total of 4709 patients with fractures admitted in 2010–2022, followed by road traffic accidents, were included. Male patients accounted for 81.6% (n = 3843) of all fractures reported. The most commonly fractured body areas were the upper limb extremities (30.05%), followed by lower limb extremities (11.30%), head or skull fracture (10.53%), spine fracture (8.83%), ribs fracture (8.52%), neck fracture (8.09%), pelvis fracture (3.44%), clavicle fracture (1.89%), and sternal fracture (0.28%). Among the upper limb fractures, the femur bone was most fractured (17.06%), and the combined tibia patella and fibula accounted for 17.69% of upper limb fractures. Conclusion: Lower limb fractures, especially femur bone fractures, are prevalent in Saudi Arabia, and caused by RTAs, especially among young males. Therefore, the concerned authorities need to employ and implement stricter traffic rules to minimize the risk of RTA fractures and their subsequent increased morbidity and mortality rates
16
Yao, Mengbi, Haibin Chang, Xiang Li e Dongxiao Zhang. "An Integrated Approach for History Matching of Multiscale-Fracture Reservoirs". SPE Journal 24, n. 04 (8 maggio 2019): 1508–25. http://dx.doi.org/10.2118/195589-pa.
Testo completoAbstract (sommario):
Summary Naturally or hydraulically fractured reservoirs usually contain fractures at various scales. Among these fractures, large-scale fractures might strongly affect fluid flow, making them essential for production behavior. Areas with densely populated small-scale fractures might also affect the flow capacity of the region and contribute to production. However, because of limited information, locating each small-scale fracture individually is impossible. The coexistence of different fracture scales also constitutes a great challenge for history matching. In this work, an integrated approach is proposed to inverse model multiscale fractures hierarchically using dynamic production data. In the proposed method, a hybrid of an embedded discrete fracture model (EDFM) and a dual-porosity/dual-permeability (DPDP) model is devised to parameterize multiscale fractures. The large-scale fractures are explicitly modeled by EDFM with Hough-transform-based parameterization to maintain their geometrical details. For the area with densely populated small-scale fractures, a truncated Gaussian field is applied to capture its spatial distribution, and then the DPDP model is used to model this fracture area. After the parameterization, an iterative history-matching method is used to inversely model the flow in a fractured reservoir. Several synthetic cases, including one case with single-scale fractures and three cases with multiscale fractures, are designed to test the performance of the proposed approach.
17
Xue, Jiao, Hanming Gu e Chengguo Cai. "Model-based amplitude versus offset and azimuth inversion for estimating fracture parameters and fluid content". GEOPHYSICS 82, n. 2 (1 marzo 2017): M1—M17. http://dx.doi.org/10.1190/geo2016-0196.1.
Testo completoAbstract (sommario):
The normal-to-shear fracture compliance ratio is commonly used as a fluid indicator. In the seismic frequency range, the fluid indicator lies between the values for isolated fluid-filled fractures and dry fractures, and it is not easy to discriminate the fluid content. Assuming that the fracture surfaces are smooth, we use [Formula: see text], with [Formula: see text] and [Formula: see text] representing the normal fracture weakness of the saturated and dry rock, to indicate fluid types, and to define a fluid influencing factor. The fluid influencing factor is sensitive to the fluid properties, the aspect ratio of the fractures, and the frequency. Conventionally, the amplitude versus offset and azimuth (AVOA) inversion is formulated in terms of the contrasts of the fracture weaknesses across the interface, assuming that the fractures are vertical with the same symmetry axis. We consider fractures with arbitrary azimuths, and develop a method to estimate fracture parameters from wide-azimuth seismic data. The proposed AVOA inversion algorithm is tested on real 3D prestack seismic data from the Tarim Basin, China, and the inverted fracture density show good agreement with well log data, except that there are some discrepancies for one of the fractured reservoir sections. The discrepancies can be ascribed to neglect of the dip angle for the tilted fractures and the conjugate fracture sets, and to the validity of the linear-slip model. The fractured reservoirs are expected to be liquid saturated, under the assumption of smooth fractures. Overall, the inverted fracture density and fluid influencing factor can be potentially used for better well planning in fractured reservoirs and quantitatively estimating the fluid effects.
18
Li, Liyong, e Seong H. Lee. "Efficient Field-Scale Simulation of Black Oil in a Naturally Fractured Reservoir Through Discrete Fracture Networks and Homogenized Media". SPE Reservoir Evaluation & Engineering 11, n. 04 (1 agosto 2008): 750–58. http://dx.doi.org/10.2118/103901-pa.
Testo completoAbstract (sommario):
Summary This paper describes a hybrid finite volume method, designed to simulate multiphase flow in a field-scale naturally fractured reservoir. Lee et al. (WRR 37:443-455, 2001) developed a hierarchical approach in which the permeability contribution from short fractures is derived in an analytical expression that from medium fractures is numerically solved using a boundary element method. The long fractures are modeled explicitly as major fluid conduits. Reservoirs with well-developed natural fractures include many complex fracture networks that cannot be easily modeled by simple long fracture formulation and/or homogenized single continuity model. We thus propose a numerically efficient hybrid method in which small and medium fractures are modeled by effective permeability, and large fractures are modeled by discrete fracture networks. A simple, systematic way is devised to calculate transport parameters between fracture networks and discretized, homogenized media. An efficient numerical algorithm is also devised to solve the dual system of fracture network and finite volume grid. Black oil formulation is implemented in the simulator to demonstrate practical applications of this hybrid finite volume method. Introduction Many reservoirs are highly fractured due to the complex tectonic movement and sedimentation process the formation has experienced. The permeability of a fracture is usually much larger than that of the rock matrix; as a result, the fluid will flow mostly through the fracture network, if the fractures are connected. This implies that the fracture connectivities and their distribution will determine fluid transport in a naturally fractured reservoir (Long and Witherspoon 1985). Because of statistically complex distribution of geological heterogeneity and multiple length and time scales in natural porous media, three approaches (Smith and Schwartz 1993) are commonly used in describing fluid flow and solute transport in naturally fractured formations:discrete fracture models;continuum models using effective properties for discrete grids; andhybrid models that combine discrete, large features and equivalent continuum. Currently, most reservoir simulators use dual continuum formulations (i.e., dual porosity/permeability) for naturally fractured reservoirs in which matrix blocks are divided by very regular fracture patterns (Kazemi et al. 1976, Van Golf-Racht 1982). Part of the primary input into these simulation models is the permeability of the fracture system assigned to the individual grid-blocks. This value can only be reasonably calculated if the fracture systems are regular and well connected. Field characterization studies have shown, however, that fracture systems are very irregular, often disconnected, and occur in swarms (Laubach 1991, Lorenz and Hill 1991, Narr et al. 2003). Most naturally fractured reservoirs include fractures of multiple- length scales. The effective grid-block permeability calculated by the boundary element method becomes expensive as the number of fractures increases. The calculated effective properties for grid-blocks also underestimates the properties for long fractures whose length scale is much larger than the grid-block size. Lee et al. (2001) proposed a hierarchical method to model fluid flow in a reservoir with multiple-length scaled fractures. They assumed that short fractures are randomly distributed and contribute to increasing the effective matrix permeability. An asymptotic solution representing the permeability contribution from short fractures was derived. With the short fracture contribution to permeability, the effective matrix permeability can be expressed in a general tensor form. Thus, they also developed a boundary element method for Darcy's equation with tensor permeability. For medium-length fractures in a grid-block, a coupled system of Poisson equations with tensor permeability was solved numerically using a boundary element method. The grid-block effective permeabilities were used with a finite difference simulator to compute flow through the fracture system. The simulator was enhanced to use a control-volume finite difference formulation (Lee et al. 1998, 2002) for general tensor permeability input (i.e., 9-point stencil for 2-D and 27-point stencil for 3-D). In addition, long fractures were explicitly modeled by using the transport index between fracture and matrix in a gridblock. In this paper we adopt their transport index concept and extend the hierarchical method:to include networks of long fractures;to model fracture as a two-dimensional plane; andto allow fractures to intersect with well bore. This generalization allows us to model a more realistic and complex fracture network that can be found in naturally fractured reservoirs. To demonstrate this new method for practical reservoir applications, we furthermore implement a black oil formulation in the simulator. We explicitly model long fractures as a two-dimensional plane that can penetrate several layers. The method, presented in this paper, allows a general description of fracture orientation in space. For simplicity of computational implementation however, both the medium-length and long fractures considered in this paper are assumed to be perpendicular to bedding boundaries. In addition, we derive a source/sink term to model the flux between matrix and long fracture networks. This source/sink allows for coupling multiphase flow equations in long fractures and matrix. The paper is organized as follows. In Section 2 black oil formulation is briefly summarized and the transport equations for three phase flow are presented. The fracture characterization and hierarchical modeling approach, based on fracture length, are discussed in Section 3. In Section 4 we review homogenization of short and medium fractures, which is part of our hierarchical approach to modeling flow in porous media with multiple length-scale fractures. In Section 5 we discuss a discrete network model of long fractures. We also derive transfer indices between fracture and effective matrix blocks. In Section 6 we present numerical examples for tracer transport in a model with simple fracture network, interactions of fractures and wells, and black oil production in a reservoir with a complex fracture network system. Finally, the summary of our main results and conclusion follows.
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Chen, Zhiming, Xinwei Liao, Kamy Sepehrnoori e Wei Yu. "A Semianalytical Model for Pressure-Transient Analysis of Fractured Wells in Unconventional Plays With Arbitrarily Distributed Discrete Fractures". SPE Journal 23, n. 06 (7 settembre 2018): 2041–59. http://dx.doi.org/10.2118/187290-pa.
Testo completoAbstract (sommario):
Summary In this paper, we present an efficient semianalytical model for pressure-transient analysis in fractured wells by considering arbitrarily distributed fracture networks. The semianalytical model included three domains: matrix, hydraulic-fracture networks, and discrete natural fractures. Using the line-source function, we developed the diffusivity equation for fluid flow in matrix. By applying the vertex-analysis technique, we eliminated the flow interplay at fracture intersections and established the diffusivity equations for fluid flow in hydraulic-fracture networks and isolated natural fractures. The pressure-transient solution of these diffusivity equations was obtained using Laplace transforms and the Stehfest numerical inversion. Results showed that with the discrete natural fractures, a “V-shaped” pressure derivative (the classical dual-porosity feature of naturally fractured reservoirs) emerged. With the hydraulic-fracture networks, the reservoir system would exhibit pressure behaviors such as “pseudoboundary-dominated flow,” “fracture-interference flow,” and “fluid-feed flow.” All these pressure characteristics were dependent on the properties and geometries of natural/hydraulic fractures. In addition, through synthetic field application, we found that different (natural/hydraulic) fracture distributions and geometries had distinct behaviors of pressure derivatives, which may provide an effective tool to identify the properties of randomly distributed natural fractures as well as complex hydraulic fractures in unconventional plays.
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Liu, Jinhui, Yuli Zhou e Jianguo Chen. "A Two-Dimensional Partitioning of Fracture–Matrix Flow in Fractured Reservoir Rock Using a Dual-Porosity Percolation Model". Energies 14, n. 8 (15 aprile 2021): 2209. http://dx.doi.org/10.3390/en14082209.
Testo completoAbstract (sommario):
Fractures and micropores have varying contributions to the gas permeability of fractured reservoirs. The quantification of the contribution of fractures and micropores that form a dual-porosity system for gas permeability is critical when attempting to accurately evaluate gas production. However, due to insufficient knowledge of fracture–matrix flow partitioning in such dual-porosity systems, it is challenging for previous models to quantitatively characterize the fracture heterogeneity and accurately evaluate the gas flow and permeability in fractured rocks. In this study, we propose a dual-porosity percolation model to quantitatively investigate the contributions of fractures and matrix micropores towards the gas permeability of fractured rocks. Using percolation theory, we establish fracture networks with complex heterogeneity, which are characterized by various fracture densities and percolation probabilities within a porous matrix with various fracture/matrix permeability ratios. The compressible Navier–Stokes and Brinkman equations were adopted to describe the gas flow in the fractures and porous matrix, respectively. The simulation results indicate that the gas permeability of the dual-porosity system has an exponential relationship with the fracture density and matrix permeability. The contribution of fractures and matrix micropores toward gas permeability can be classified by establishing a two-dimensional partitioning of the fracture–matrix flow related to the fracture heterogeneity and fracture/matrix permeability ratio. The contribution of matrix micropores cannot be neglected if the fracture density is lower than a critical value.
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Abdel-Rahman, Hoshang. "Causes and types of complete denture fracture". Zanco Journal of Medical Sciences 15, n. 3 (1 dicembre 2011): 36–40. http://dx.doi.org/10.15218/zjms.2011.031.
Testo completoAbstract (sommario):
Background and objectives: determine the causes and types of complete denture fractures. Methods: The study was performed in the Hawler medical university, college of Dentistry Department of Prosthodontics. The number of fractured complete denture collected was 290 from patients aged 35-80 years of both genders. The (causes of denture fracture, the type of fracture and the history of previous recurrent fractures) were recorded. Results: : The main cause of denture fracture was poor fitting (40%), followed by poor occlusal relation (21%). Midline fracture was the commonest type of fracture (59%). From the study (51%) of the dentures had previously been repaired once or more. The ratio of lower to upper complete denture fractures was approximately 3:1; most of the fractured dentures (56%) were those of males. Conclusion: The causes of the fracture were divided into material factors and clinical/ technical factors. Denture fractures can be reduced by following prosthodontic principles, analyzing proper fit, eliminating occlusal interferences and using high impact polymers or metal reinforced.
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Li, Jianxiong, Shiming Dong, Wen Hua, Xiaolong Li e Xin Pan. "Numerical Investigation of Hydraulic Fracture Propagation Based on Cohesive Zone Model in Naturally Fractured Formations". Processes 7, n. 1 (8 gennaio 2019): 28. http://dx.doi.org/10.3390/pr7010028.
Testo completoAbstract (sommario):
Complex propagation patterns of hydraulic fractures often play important roles in naturally fractured formations due to complex mechanisms. Therefore, understanding propagation patterns and the geometry of fractures is essential for hydraulic fracturing design. In this work, a seepage–stress–damage coupled model based on the finite pore pressure cohesive zone (PPCZ) method was developed to investigate hydraulic fracture propagation behavior in a naturally fractured reservoir. Compared with the traditional finite element method, the coupled model with global insertion cohesive elements realizes arbitrary propagation of fluid-driven fractures. Numerical simulations of multiple-cluster hydraulic fracturing were carried out to investigate the sensitivities of a multitude of parameters. The results reveal that stress interference from multiple-clusters is responsible for serious suppression and diversion of the fracture network. A lower stress difference benefits the fracture network and helps open natural fractures. By comparing the mechanism of fluid injection, the maximal fracture network can be achieved with various injection rates and viscosities at different fracturing stages. Cluster parameters, including the number of clusters and their spacing, were optimal, satisfying the requirement of creating a large fracture network. These results offer new insights into the propagation pattern of fluid driven fractures and should act as a guide for multiple-cluster hydraulic fracturing, which can help increase the hydraulic fracture volume in naturally fractured reservoirs.
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Xu, Chaoshui, Shaoqun Dong, Hang Wang, Zhihe Wang, Feng Xiong, Qinghui Jiang, Lianbo Zeng, Leon Faulkner, Zhao Feng Tian e Peter Dowd. "Modelling of Coupled Hydro-Thermo-Chemical Fluid Flow through Rock Fracture Networks and Its Applications". Geosciences 11, n. 4 (29 marzo 2021): 153. http://dx.doi.org/10.3390/geosciences11040153.
Testo completoAbstract (sommario):
Most rock masses contain natural fractures. In many engineering applications, a detailed understanding of the characteristics of fluid flow through a fractured rock mass is critically important for design, performance analysis, and uncertainty/risk assessment. In this context, rock fractures and fracture networks play a decisive role in conducting fluid through the rock mass as the permeability of fractures is in general orders of magnitudes greater than that of intact rock matrices, particularly in hard rock settings. This paper reviews the modelling methods developed over the past four decades for the generation of representative fracture networks in rock masses. It then reviews some of the authors’ recent developments in numerical modelling and experimental studies of linear and non-linear fluid flow through fractures and fracture networks, including challenging issues such as fracture wall roughness, aperture variations, flow tortuosity, fracture intersection geometry, fracture connectivity, and inertia effects at high Reynolds numbers. Finally, it provides a brief review of two applications of methods developed by the authors: the Habanero coupled hydro-thermal heat extraction model for fractured reservoirs and the Kapunda in-situ recovery of copper minerals from fractures, which is based on a coupled hydro-chemical model.
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STANTON, J. S., J. J. DIAS e F. D. BURKE. "Fractures of the Tubular Bones of the Hand". Journal of Hand Surgery (European Volume) 32, n. 6 (dicembre 2007): 626–36. http://dx.doi.org/10.1016/j.jhse.2007.06.017.
Testo completoAbstract (sommario):
Age related differences in demographics, morphology, treatment and outcome were investigated in 701 fractures of the metacarpals or phalanges, including fracture-dislocations, in 655 patients. Fractures mainly due to sport occurred in 184 children, usually after 10 years of age. The base of the proximal phalanx was especially vulnerable. Thirty-seven percent of 256 young adults fractured their fifth metacarpal. The thumb was rarely involved. Half of these two groups fractured the fifth ray. Older adults had more fractures of the distal phalanx and displaced extraarticular fractures requiring stabilisation. Women predominated in the patients over 65. Forty percent of this group sustained their fracture on the road and more fractures involved the thumb, were oblique, intraarticular or multiple than in other groups. Detailed analysis of 423 X-rays demonstrated that only 10% of 70 intraarticular fractures and 19% of 363 extraarticular fractures were completely undisplaced. Patient response to postal questionnaire based outcome assessment using SF-12, MHQ was very poor.
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Noor, Marjan, Raheel Hassan, Abid Hussain Bukhari e Rashida Hilal. "Frequency of Parasymphysis Fracture in Mandibular Fractures Due to Road Traffic Accidents". Pakistan Journal of Medical and Health Sciences 16, n. 9 (30 settembre 2022): 333–34. http://dx.doi.org/10.53350/pjmhs22169333.
Testo completoAbstract (sommario):
Objective: To determine the frequency of parasymphysis fracture in mandibular fractures due to road traffic accidents. Study Type: Cross-sectional study Duration and Place of Study: Department of OMF Surgery Ayub Teaching Hospital, Abbottabad from 1st December 2019 to 30thMay 2020 Methodology: One hundred and forty eight patients were shifted to the Radiology Department for X-rays of mandible . Fractures of mandible especially fracture of parasymphysis were seen. Results: The mean age was 47.46±21.25 years. Fractured parasymphysis was found in 75 (82%) male patients and female patients were 14% (8/57). Conclusions: The gender was found to be significantly associated with the outcome i.e. parasymphysis fracture in mandibular fractures due to road traffic accidents. The age, number of fractures and type of fractures were not found to be significantly associated with the outcome i.e. parasymphysis fracture in mandibular fractures due to road traffic accidents. Keywords: Parasymphysis fracture, Mandibular fractures, Facial injury
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Wu, Na, Zhengzhao Liang, Yan Tao, Ting Ai e Guijie Li. "Sensitivity Analysis of Fracture Geometry Parameters on the Mechanical Behavior of Rock Mass with an Embedded Three-Dimensional Fracture Network". Applied Sciences 12, n. 18 (16 settembre 2022): 9284. http://dx.doi.org/10.3390/app12189284.
Testo completoAbstract (sommario):
The existence of fractures has a significant influence on the mechanical properties of a rock mass. The sensitivity of the rock mass’s mechanical properties to the fracture’s geometric parameters is conducive to improving the measurement accuracy of fractured rock mass engineering. Firstly, the fracture geometric parameters in the dam site area of Lianghekou Hydropower Station were counted using the ShapeMetriX3D system. Then, the effect of the fracture’s geometric parameters on the deformation characteristics, failure mode, and mechanical parameters of the rock mass were investigated based on the RFPA3D under the uniaxial compression test. The results showed that the stress–strain curves of the fractured rock mass mainly exhibited elastic-brittle characteristics. The failure pattern of the fractured rock mass was mainly defined by a compressive-shear composite. Additionally, the influence of the fracture’s geometric parameters on the uniaxial compressive strength (UCS) was greater than that of elastic modulus. The sensitivity of the UCS to fracture trace length was more significant.
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Liu, Hong, Jiang Xin Feng, Ya Long Zhang, Yi Xing Yue, Tao Zhang e Yu Pan. "Mechanism for Network Fracturing in Natural Fractured Reservoir". Advanced Materials Research 868 (dicembre 2013): 718–24. http://dx.doi.org/10.4028/www.scientific.net/amr.868.718.
Testo completoAbstract (sommario):
By the methods of in-house experiment and theory analysis, the fracture initiation, stretch and interconnected mechanism of natural fracture is studied in the fracturing process of main fracture and branch fracture extending. The results have shown that, the hydraulic fracture in fractured formation is composed of a few main fractures in large size and many s secondary fractures in small size. The main fracture has the extending trend with the maximum crustal stress direction. The direction of sub fracture is network along the maximum crustal stress. The higher the degree of natural fractures, the difference between maximum and minimum crustal stress smaller. And the natural fracture is easier to form larger fracture. Fracture orientation and fracture width are determined by different combinations of natural fractures and the relative orientation with the maximum crustal stress.
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Al-Rubaie, Ali, e Hisham Khaled Ben Mahmud. "A numerical investigation on the performance of hydraulic fracturing in naturally fractured gas reservoirs based on stimulated rock volume". Journal of Petroleum Exploration and Production Technology 10, n. 8 (17 agosto 2020): 3333–45. http://dx.doi.org/10.1007/s13202-020-00980-8.
Testo completoAbstract (sommario):
Abstract All reservoirs are fractured to some degree. Depending on the density, dimension, orientation and the cementation of natural fractures and the location where the hydraulic fracturing is done, preexisting natural fractures can impact hydraulic fracture propagation and the associated flow capacity. Understanding the interactions between hydraulic fracture and natural fractures is crucial in estimating fracture complexity, stimulated reservoir volume, drained reservoir volume and completion efficiency. However, because of the presence of natural fractures with diffuse penetration and different orientations, the operation is complicated in naturally fractured gas reservoirs. For this purpose, two numerical methods are proposed for simulating the hydraulic fracture in a naturally fractured gas reservoir. However, what hydraulic fracture looks like in the subsurface, especially in unconventional reservoirs, remain elusive, and many times, field observations contradict our common beliefs. In this study, the hydraulic fracture model is considered in terms of the state of tensions, on the interaction between the hydraulic fracture and the natural fracture (45°), and the effect of length and height of hydraulic fracture developed and how to distribute induced stress around the well. In order to determine the direction in which the hydraulic fracture is formed strikethrough, the finite difference method and the individual element for numerical solution are used and simulated. The results indicate that the optimum hydraulic fracture time was when the hydraulic fracture is able to connect natural fractures with large streams and connected to the well, and there is a fundamental difference between the tensile and shear opening. The analysis indicates that the growing hydraulic fracture, the tensile and shear stresses applied to the natural fracture.
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Lee, Seung, Jae Sim, Do Han e Min Kim. "A Transpatellar Approach to Treat Distal Femoral Type C3 Fractures Combined with Patellar Fractures". Journal of Knee Surgery 31, n. 09 (6 febbraio 2018): 905–12. http://dx.doi.org/10.1055/s-0038-1626734.
Testo completoAbstract (sommario):
AbstractWe report our surgical method used to treat type C distal femur fractures accompanied by patella fractures whereby we approach the articular surface of the femur through the already-fractured patella. We treated 10 patients with type C3 distal femur and patella fractures between May 2013 and April 2015. Because the patella was fractured in all cases, we could approach the articular surface of the distal femur through the transverse gap between the retracted patellar fracture fragments, “transpatellar approach.” Any surgical complications were recorded. Knee function was evaluated using the Böstman system. The average age of the 10 patients (8 males) was 42.9 years (range, 22.0–58.0 years). All distal femur fractures were type C3, combined with patella fractures. Bony union of the distal femur and patella was achieved in all but one patient, who required an additional bone graft (without any change in the implant). Overall, three patients (30%) reported excellent results and seven (70%) reported good results, based on the Böstman system. A midline anterior approach through a patella fracture adequately exposes the entire joint surface of the distal femur, except the posterior surface. This approach is useful when treating a type C distal femur fracture accompanied by a patella fracture. The level of evidence is IV.
30
Wang, E. Z., Z. Q. Yue, L. G. Tham, Y. Tsui e H. T. Wang. "A dual fracture model to simulate large-scale flow through fractured rocks". Canadian Geotechnical Journal 39, n. 6 (1 dicembre 2002): 1302–12. http://dx.doi.org/10.1139/t02-068.
Testo completoAbstract (sommario):
Discrete fracture network models can be used to study groundwater flow in fractured rock masses. However, one may find that it is not easy to apply such models to practical projects as it is difficult to investigate every fracture and measure its hydraulic parameters. To overcome such difficulties, a dual fracture model is proposed. Taking into account the hydraulic characteristics of the various elements of the fracture system, a hydrogeological medium is assumed to consist of two components: the dominant fracture network and the fractured rock matrix. As the dominant fracture network consists of large fractures and faults, it controls the groundwater flow in rock masses. Depending on the permeabilities of the in-fill materials, these fractures and faults may serve as channels or barriers of the flow. The fractured rock matrix, which includes rock blocks and numerous small fractures, plays a secondary role in groundwater flow in such medium. Although the small fractures and rock blocks possess low permeability, their numbers and their total porosity are relatively large. Therefore, they provide large volume for groundwater storage. In this paper, the application of the proposed model to simulate the groundwater flow for a hydropower station before and after reservoir storage is reported. The implications of the results on the design of the station are also highlighted.Key words: seepage flow, dual fracture model, dominant fracture, fractured rock matrix, case studies, rock-filled dam.
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Morimoto, Susana, Wilma K. C. Lia, Flavia Gonçalves, Denis Yudi Nagase, Thais Gimenez, Daniela Procida Raggio e Mutlu Özcan. "Risk Factors Associated with Cusp Fractures in Posterior Permanent Teeth—A Cross-Sectional Study". Applied Sciences 11, n. 19 (7 ottobre 2021): 9299. http://dx.doi.org/10.3390/app11199299.
Testo completoAbstract (sommario):
Objectives: This cross-sectional study aimed to evaluate the frequency and risk factors associated with cusp fractures in posterior permanent teeth. Methods: Patients presented cusp fractures on posterior permanent teeth, clinically assessed in up to 7 days after the event, and requesting dental treatment at two public services were included in this cross-sectional study. Fractured teeth already treated, with antagonist absence, or with prosthesis (total or removable) were excluded. Demographic and clinical data were collected to draw the patient profiles and establish how teeth were affected individually. Statistical analysis was performed by the Fisher exact test, and uni- and multivariate logistic regression (α = 0.05). Results: One hundred and seventy-seven (177) patients from 16 to 66 years old (±41.56), from 1998 to 2016, were included in this study. Non-functional and lingual cusps presented a higher fracture than functional and buccal cusps, respectively. Fractures were more common in teeth with isthmus wider than 1/3 of the intercuspid distance and/or more than three restored surfaces. Teeth with endodontic treatment presented a higher subgingival fracture. On lingual cusps, fracture type and location were significantly associated, being that total fractures were 3.2 times more likely to occur than partial fractures, and subgingival were 3.62 times more likely to occur than supragingival fractures. Conclusion: Indications of classic protection on functional cusps (LUBL) was refuted since, generally, nonfunctional cusps fractured more than the functional cusps. However, upper pre-molars showed more fractures in functional cusps and lower molars presented more fractures on the nonfunctional cusps. In general, lingual cusps were the most fractured and were associated with a higher prevalence of severe fractures (total fractures at the subgingival level). Fractures were more common in teeth where the restoration had an isthmus wider than 1/3 of the intercuspid distance and/or involved more than three restored surfaces. Most of the patients did not show previous symptoms and signs. Overall, teeth with endodontic treatment presented a higher subgingival fracture.
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Abedi, Behbood, Mohammad Hossein Ghazanfari e Riyaz Kharrat. "Experimental Study of Polymer Flooding in Fractured Systems Using Five-Spot Glass Micromodel: The Role of Fracture Geometrical Properties". Energy Exploration & Exploitation 30, n. 5 (ottobre 2012): 689–705. http://dx.doi.org/10.1260/0144-5987.30.5.689.
Testo completoAbstract (sommario):
Water flooding is being widely used in the petroleum industry and has been considered as a simple inexpensive secondary recovery method. But in fractured formations, existence of fracture system in reservoir rock induces an adverse effect on oil recovery by water flooding. Polymer flooding has been successfully applied as an alternative enhanced oil recovery method in fractured formations. But, the role of fracture geometrical properties on macroscopic efficiency of polymer flooding is not yet well-understood, especially in fractured five-spot systems. In this work five-spot glass micromodel, because of micro-visibility, ease of multiple experimentations and also presence of the unexplored issues, was used to experimentally investigate the influence of fracture geometrical characteristics such as fracture orientation, fracture spacing, fracture overlap and etc on the macroscopic efficiency of polymer flooding. The tests were performed on the fractured models which are initially saturated with the crude oil at fixed flow rate conditions and in a horizontally mounting. The results revealed that the macroscopic efficiency of polymer flooding depends on fracture geometrical properties. Fracture orientation showed more imposing effect than other fracture geometrical properties, and fracture with 45 degree inclination to the mean flow direction, gives greatest oil recovery factor. Large spacing fractures give more recovery than small spacing ones and in case of overlapping, fractures with less overlapping help polymer to better propagate which could be related to their greater effective fracture length. This pre-called effect could be responsible to show how continuity and width to length ratio of fractures affect recovery factor, less fracture discontinuity as well as more length to width ratio of fracture give more swept zone. Also, increasing number of fractures decreases oil recovery factor. The results of this work can be helpful to better understanding the role of fracture geometrical properties on macroscopic efficiency of polymer flooding in five-spot fractured systems.
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Kelishadi, Shahrooz S., Matthew R. Zeiderman, Karan Chopra, Joseph A. Kelamis, Gerhard S. Mundinger e Eduardo D. Rodriguez. "Facial Fracture Patterns Associated with Traumatic Optic Neuropathy". Craniomaxillofacial Trauma & Reconstruction 12, n. 1 (marzo 2019): 39–44. http://dx.doi.org/10.1055/s-0038-1641172.
Testo completoAbstract (sommario):
Traumatic optic neuropathy (TON) is rare. The heterogeneity of injury patterns and patient condition on presentation makes diagnosis difficult. Fracture patterns associated with TON have never been evaluated. Retrospective review of 42 patients diagnosed with TON at the R. Adams Cowley Shock Trauma Center from May 1998 to August 2010 was performed. Thirty-three patients met criteria for study inclusion of fracture patterns. Additional variables measured included patient demographics and mechanism. Cluster analysis was used to form homogenous groups of patients based on different fracture patterns. Fracture frequency was analyzed by group and study population. Visual depiction of fracture patterns was created for each group. Cluster analysis of fracture patterns yielded five common “groups” or fracture patterns among the study population. Group 1 ( n = 3, 9%) revealed contralateral lateral orbital wall (100%), zygoma (67%), and nasal bone (67%) fractures. Group 2 ( n = 7, 21%) demonstrated fractures of the frontal bone (86%), nasal bones (71%), and ipsilateral orbital roof (57%). Group 3 ( n = 14, 43%) involved fractures of the ipsilateral zygoma (100%), lateral orbital wall (29%), as well as frontal and nasal bones (21% each). Group 4 ( n = 5, 15%) consisted of mid- and upper-face fractures; 100% fractured the ipsilateral orbital floor, medial and lateral walls, maxilla, and zygoma; 80% fractured the orbital roof and bilateral zygoma. Group 5 ( n = 4, 12%) was characterized by fractures of the ipsilateral orbital floor, medial and lateral orbital walls (75% each), and orbital roof (50%). A notably high 15 of 33 patients (45%) sustained penetrating trauma. Our study demonstrates five fracture pattern groups associated with TON. Zygomatic, frontal, nasal, and orbital fractures were the most common. Fractures with a combination of frontal, nasal, and orbital fractures are particularly concerning and warrant close attention to the eye.
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van Heerden, Frans G., Robert M. Kirberger e Marthinus J. Hartman. "Long Bone Fractures in Impala (Aepyceros melampus): A Classification System and Review of 55 Cases". Veterinary and Comparative Orthopaedics and Traumatology 32, n. 05 (3 giugno 2019): 408–19. http://dx.doi.org/10.1055/s-0039-1691818.
Testo completoAbstract (sommario):
Abstract Objective The purpose of this study was to introduce a modified-Unger fracture classification in impala and report the findings of 58 long bone fractures classified according to this system. Methods This was a retrospective radiographical study evaluating 122 radiographs of 58 long bone fractures in 55 impala. The Unger fracture classification was modified and fracture illustrations for the metacarpal and metatarsal bones added. Each fracture was classified and assigned a four symbol α-numeric code using our classification. The patient signalment, skeletal maturity, fracture-associated soft tissue changes, presence of fissure lines, periosteal reaction and cause of the fracture were recorded. Results The overall fracture distribution based on location, found tibial (n = 17) fractures to be the most common fractured long bone. When combined, the majority of fractures involved the metacarpal and metatarsal bones (n = 23). Forty five of 58 fractures occurred in the diaphyseal bone segment. In all long bones, the distribution based on complexity was simple (n = 27), wedge (n = 16) and multi-fragmentary (n = 15) fractures. Thirty one of 58 fractures were open and fissure lines were detected in 20 of 58 fractures. Clinical Significance Our modified-Unger fracture classification was applicable in classifying 58 impala long bone fractures. This classification should provide the basis for further advances in veterinary and comparative ungulates, and particularly the antelopes, orthopaedics and traumatology.
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Liu, Mengxuan. "Research on fracture trend of repeated fracturing". Journal of Physics: Conference Series 2247, n. 1 (1 aprile 2022): 012016. http://dx.doi.org/10.1088/1742-6596/2247/1/012016.
Testo completoAbstract (sommario):
Abstract The fracture trend of repeated fracturing is directly related to the effect of repeated fracturing and whether it can effectively expand the swept volume. In this paper, a large-scale hydraulic fracturing process simulation device is used to conduct laboratory experiments on fractured reservoirs to study the initiation and extension of repeated fracturing fractures under different stress states. The experimental results show that new fractures are easy to extend from the natural fractures near the wellbore, and the initiation pressure of the secondary fracturing is reduced due to the inducing effect of the initial fractures. The conclusion has a certain guiding function for the prediction of repeated fracturing fracture propagation in field fractured reservoirs, and it is of great significance for fracturing construction.
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Mizuhashi, Fumi, Yuko Watarai e Ichiro Ogura. "Diagnosis of Vertical Root Fractures in Endodontically Treated Teeth by Cone-Beam Computed Tomography". Journal of Imaging 8, n. 3 (23 febbraio 2022): 51. http://dx.doi.org/10.3390/jimaging8030051.
Testo completoAbstract (sommario):
The purpose of this study was to investigate the characteristics and the detection ability of vertical root fractures in endodontically treated teeth by intraoral radiography and cone-beam computed tomography (CBCT). CBCT images of 50 patients with root fractures in endodontically treated teeth were reviewed, and 36 vertical root fractures were taken in this study. The cause of fracture, core construction, kind of teeth, and fracture direction (bucco-lingual and mesio-distal fractures) were investigated. Detection ability of vertical root fractures by intraoral radiography and CBCT was also examined. Statistical analyses concerning the characteristics were performed by χ2 test, and the detection ability was analyzed by cross-tabulation. All of the fractured teeth were nontraumatized teeth. The vertical root fracture occurrence was not differed by core construction. The vertical root fracture number was largest at the premolar teeth (p = 0.005), and the number of the bucco-lingual fracture was larger than the mesio-distal fracture (p = 0.046). Vertical root fractures were detectable using CBCT, while undetectable by intraoral radiography (p < 0.001). Vertical root fractures occurred easily in premolar teeth with bucco-lingual direction, and CBCT is an adequate radiographic method to diagnose vertical root fracture.
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Chang, Xu, Junjie Liu, Chun An Tang, Yong Bin Zhang e Juan Xia Zhang. "Numerical Approach to Fracture Spacing in Two Layered Material". Key Engineering Materials 297-300 (novembre 2005): 750–55. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.750.
Testo completoAbstract (sommario):
Equally spaced opening-mode fractures always evolve in top layer attached to underlying layer. With a newly developed Material Failure Process Analysis code (MFPA2D), we have firstly investigated the stress distribution between two adjacent fractures as a function of the fracture-spacing-to-layer-thickness ratio using a two-layer model with a fractured top layer. The numerical results indicate the horizontal stress perpendicular to the fractures near the top surface changes from tensile to compressive when the fracture-spacing-to-layer-thickness ratio changes from greater than to less than a critical value. Then, the process from fracture initiation to fracture saturation is numerically modeled. The modeling of fracture process shows that the fractures initiate at the top surface and propagate to the interface between the two layers in the first stage. In the following stage, new fractures can infill between the earlier formed fractures and they always initiate at the interface and propagate to the top surface. Numerical simulation clearly demonstrates that the stress state transition precludes further infilling of fractures and the fracture spacing reaches a constant state, i.e. the so-called fracture saturation.
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Cao, Xusheng, Jichuan Ren, Shunyuan Xin, Chencheng Guan, Bing Zhao e Peixuan Xu. "Study of Acid Fracturing Strategy with Integrated Modeling in Naturally Fractured Carbonate Reservoirs". Processes 12, n. 4 (17 aprile 2024): 808. http://dx.doi.org/10.3390/pr12040808.
Testo completoAbstract (sommario):
Natural fractures and wormholes strongly influence the performance of acid fracturing in naturally fractured carbonate reservoirs. This work uses an integrated model to study the effects of treatment parameters in acid fracturing in different reservoir conditions. Hydraulic fracture propagation, wormhole propagation, complex fluid leak-off mediums, and heat transfer are considered in the modeling. The model is validated in several steps by analytical solutions. The simulation results indicated that natural fractures and wormholes critically impact acid fracturing and can change the predicted outcomes dramatically. The high permeability reservoirs with conductive natural fractures or low permeability reservoirs with natural fracture networks showed the highest stimulation potential in applying acid fracturing technology. The optimal acid injection rate depends on natural fracture geometry and reservoir permeability. This study also observed that obtaining a high production index is difficult because natural fractures and wormholes reduce the acid efficiency during acid fracturing. Building an acid-etched fracture system consisting of acid-etched natural fractures and hydraulic fractures may help us better stimulate the naturally fractured carbonate reservoirs. The paper illustrates a better understanding of the effects of the treatment design parameters on productivity. It paves a path for the optimal design of acid fracturing treatment for heterogeneous carbonate reservoirs.
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Rahim, Ashfaq ur, Sadiq Ali, Muhammad Nauman, Tannaza Qayyum, Abdullah Khan, Mohammad Abdullah Khan e Zahid Iqbal. "Comparison of Preauricular Approach Versus Retromandibular Approach in Management of Condylar Fractures". Pakistan Journal of Medical and Health Sciences 15, n. 8 (26 agosto 2021): 2137–40. http://dx.doi.org/10.53350/pjmhs211582137.
Testo completoAbstract (sommario):
Objectives: Surgical treatment of patients with multiple mandibular fractures involving condylar segments may be a difficult proposition for a maxillofacial surgeon. These fractures can be double or triple fractures of the lower mandible and can also be associated with other fractures of the face. While many authors have suggested that the conventional approach to reducing and stabilizing a mandibular symphysis / para-symphysis fracture is appropriate before addressing a fractured condyle, there is another school of thought that suggests that the condylar segment should be reduced and repaired first. This article aims to review the results of operations where the reduction and fixation of a fractured condyle is performed prior to other associated mandible fractures, and to explore the effectiveness of various surgical methods including preauricular and retromandibular proposed in this case. Place and Duration: In the Oral and Maxillofacial surgery department of Faryal Dental College, Lahore for two-years duration from Jan 2018 to Jan 2020. Material and methods: The study included 60 surgically treated patients with multiple mandible fractures (double / triple), including the condyle component. For treatment of the fractured condylar segments, the preauricular and retromandibular (anterior parotid-transmasseteric) approach was used. Results: Condyle fracture was the first segment to be managed during sequencing of surgical treatment, regardless of the method used. First, good reduction and stabilization have been achieved with limited complications in treating a condyle fracture. Conclusion: While it is the surgeon's prerogative to sort multiple mandible fractures, addressing the condylar segment first provides the operator with a viable alternative to the conventional technique. Key words: condylar fractures, multiple mandibular fractures, preauricular approach, retromandibular approach
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Hadley, Mark N., Curtis A. Dickman, Carol M. Browner e Volker K. H. Sonntag. "Acute Traumatic Atlas Fractures: Management and Long Term Outcome". Neurosurgery 23, n. 1 (1 giugno 1988): 31–35. http://dx.doi.org/10.1227/00006123-198807000-00007.
Testo completoAbstract (sommario):
ABSTRACT Fractures of the 1st cervical vertebra (C1) represent 7% of all acute cervical spine fractures. Isolated atlas fractures are most commonly bilateral or multiple fractures through the ring of C1. Frequently (44% of cases), the atlas will be fractured in combination with the axis. Treatment of isolated C1 fractures should be governed by the rules of Spence. The treatment of combination C1-C2 fractures is dictated by the type and severity of the C2 fracture. Experience with 57 cases of acute atlas fractures is reviewed. Nonoperative external immobilization was used in 53 patients (with 1 failure), and early surgical wiring and fusion were performed in 4 patients. The long term outcome from an atlas fracture is good (median follow-up, 40 months).
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Baird, Alan F., J. Michael Kendall e Doug A. Angus. "Frequency-dependent seismic anisotropy due to fractures: Fluid flow versus scattering". GEOPHYSICS 78, n. 2 (1 marzo 2013): WA111—WA122. http://dx.doi.org/10.1190/geo2012-0288.1.
Testo completoAbstract (sommario):
Anisotropy is a useful attribute for the detection and characterization of aligned fracture sets in petroleum reservoirs. Unfortunately, many of the traditional effective medium theories for modeling the seismic properties of fractured rock are insensitive to the size of the constituent fractures. For example, the same pattern of anisotropy may be produced by a high concentration of small, stiff cracks or by a lower concentration of large, compliant fractures. The distinction between these models is important for assessing permeability anisotropy because fluid flow is dominated by the largest fractures. One method to gain further insight is through the analysis of frequency-dependent shear-wave splitting in microseismic data because fracture compliance is frequency dependent, and microseismic data are relatively rich in frequency content. We compared two potential mechanisms causing frequency-dependent compliance of fractures: (1) squirt flow in fractured porous rock and (2) wave scattering over rough fractures. Both models showed a sensitivity to average fracture size or compliance of the constituent fractures, and thus they provide a potential means to differentiate between anisotropy produced by small cracks or large fractures. We used both mechanisms to model frequency-dependent anisotropy data obtained from a fractured gas reservoir and invert for fracture parameters. Under certain conditions, the squirt-flow mechanism can cause significant frequency dependence in the microseismic band. However, the model is highly sensitive to the empirically derived mineral-scale relaxation time, which is poorly known and requires laboratory measurements to constrain. Conversely, producing a similar frequency response using the scattering model requires implausible fracture parameters; therefore, the squirt-flow model appears to be the most likely mechanism for microseismic applications. At higher frequencies, however, scattering may become more significant. Care should be taken when upscaling ultrasonic laboratory results for field-scale problems because different mechanisms may be at play within different frequency bands.
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Liu, Bin, Chen Xu, Junchang Sun e Hongqi Yuan. "Analysis of the Migration of Carbon Dioxide in Deep Saline Fractured Aquifer". International Journal of Energy 2, n. 3 (22 maggio 2023): 49–52. http://dx.doi.org/10.54097/ije.v2i3.9341.
Testo completoAbstract (sommario):
In order to control greenhouse gases and protect the environment, carbon dioxide emission reduction has become a global research hotspot. Fractures in the deep saline aquifer enhance the heterogeneity of the aquifer, and have an important effect on CO2 migration, thus the detailed description and characterization of fractures in geological structure are very important. Existing research on the impact of fractures on CO2 migration, however, ignores the role that the fractures' characteristics play in this process. This work aims at addressing this gap. Based on the embedded discrete fractured model (EDFM), we quantified the role of the fractures in the mechanism of CO2 migration and studied the length, aperture, and orientation of the fractures. It is found that the CO2 plume takes the fracture as its preferred channel and changes the migration direction. The longer the fracture length and wider the fracture aperture, the faster the CO2 migration rate is. The change in fracture orientation mainly affects the migration direction of the CO2 plume. Due to the different angles of the plume entering the fracture, the influences on the CO2 migration rate are also different. When the orientation is 45°, the CO2 migration rate is the fastest, while it is the slowest at 135°. When there is a complex fracture network in the aquifer, the heterogeneity of the aquifer is enhanced. Compared with the non-fractured aquifer, the direction and rate of CO2 migration are greatly changed, and the instability of CO2 sequestration is increased.
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Kuchuk, Fikri, Denis Biryukov e Tony Fitzpatrick. "Fractured-Reservoir Modeling and Interpretation". SPE Journal 20, n. 05 (20 ottobre 2015): 983–1004. http://dx.doi.org/10.2118/176030-pa.
Testo completoAbstract (sommario):
Summary Fractures are common features of many well-known reservoirs. Naturally fractured reservoirs (NFRs) consist of fractures in igneous, metamorphic, and sedimentary rocks (matrix). Faults in many naturally fractured carbonate reservoirs often have high-permeability zones and are connected to numerous fractures with varying conductivities. In many NFRs, faults and fractures frequently have discrete distributions rather than connected-fracture networks. Because faulting often creates fractures, faults and fractures should be modeled together. Accurately modeling NFR pressure-transient behavior is important in hydrogeology, the earth sciences, and petroleum engineering, including groundwater contamination to shale gas and oil reservoirs. For more than 50 years, conventional dual-porosity-type models, which do not include any fractures, have been used for modeling fluid flow in NFRs and aquifers. They have been continuously modified to add unphysical matrix-block properties such as matrix skin factor. In general, fractured reservoirs are heterogeneous at different length scales. It is clear that even with millions of gridblocks, numerical models may not be capable of accurately simulating the pressure-transient behavior of continuously and discretely NFRs containing variable-conductivity fractures. The conventional dual-porosity-type models are obviously an oversimplification; their serious limitations for interpreting well-test data from NFRs are discussed in detail. These models do not include wellbore-intersecting fractures, even though they dominate the pressure behavior of NFRs for a considerable length of testing time. Fracture conductivities of unity to infinity dominate transient behavior of both continuously and discretely fractured reservoirs, but again, dual-porosity models do not contain any fractures. Our fractured-reservoir model is capable of treating thousands of fractures that are periodically or arbitrarily distributed with finite- and/or infinite conductivities, different lengths, densities, and orientations. Appropriate inner-boundary conditions are used to account for wellbore-intersecting fractures and direct wellbore contributions to production. Wellbore-storage and skin effects in bounded and unbounded systems are included in the model. Three types of damaged-skin factors that may exist in wellbore-intersecting fracture(s) are specified. With this highly accurate model, the pressure-transient behavior of conventional dual-porosity-type models are investigated, and their limitations and range of applicability are identified. The behavior of the triple-porosity models is also investigated. It is very unlikely that triple-porosity behavior is caused by the local variability of matrix properties at the microscopic level. Rather, it is caused by the spatial variability of conductivity, length, density, and orientation of the fracture distributions. Finally, we have presented an interpretation of a field-buildup-test example from an NFR by use of both conventional dual-porosity models and our fractured-reservoir model. A substantial part of this paper is a review and discussion of the earlier work on NFRs, including the authors’ work.
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Qiu, Xiangliang, Chengqian Tan, Yuanyuan Lu e Shuai Yin. "Evaluation of fractures using conventional and FMI logs, and 3D seismic interpretation in continental tight sandstone reservoir". Open Geosciences 14, n. 1 (1 gennaio 2022): 530–43. http://dx.doi.org/10.1515/geo-2022-0372.
Testo completoAbstract (sommario):
Abstract Due to the complex pore structures and strong heterogeneity of fractured reservoirs, it is a hot and difficult point in petroleum geology to identify fractures using logging principles. In this paper, taking the tight sandstone reservoir of the Chang 8 Member in the Huanjiang Oilfield as an example, field outcrops, cores, thin sections, and logging identification methods were used for quantitative description and fine logging evaluation of fractures. The research shows that high-angle, medium-low-angle, near-vertical, and horizontal fractures are developed in the Chang 8 Member of the Huanjiang Oilfield. The main ones are high-angle fractures, followed by horizontal fractures with a low degree of fillings. Under the constraints of core and imaging logging data, three fracture sensitivity logging parameters of acoustic wave time difference, natural gamma, and dual induction-octalateral resistivity were optimized, and a comprehensive fracture probability index was proposed. Seventy-nine fracture development intervals were identified based on log curve characteristics and fracture probability indexes. The coincidence rate of fracture logging identification results with the core observation and imaging logging interpretation is 80.6%. The research results can provide a theoretical basis for the efficient development of fractured continental tight sandstone reservoirs in similar areas.
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Yang, Xiangtong, Yuanwei Pan, Wentong Fan, Yongjie Huang, Yang Zhang, Lizhi Wang, Lipeng Wang et al. "Case Study: 4D Coupled Reservoir/Geomechanics Simulation of a High-Pressure/High-Temperature Naturally Fractured Reservoir". SPE Journal 23, n. 05 (21 giugno 2018): 1518–38. http://dx.doi.org/10.2118/187606-pa.
Testo completoAbstract (sommario):
Summary The Keshen Reservoir is a naturally fractured, deep, tight sandstone gas reservoir under high tectonic stress. Because the reservoir matrix is very tight, the natural-fracture system is the main pathway for gas production. Meanwhile, stimulation is still required for most production wells to provide production rates that sufficiently compensate for the high cost of drilling and completing wells to access this deep reservoir. Large depletion (and related stress change) was expected during the course of the production of the field. The dynamic response of the reservoir and related risks, such as reduction of fracture conductivity, fault reactivation, and casing failure, would compromise the long-term productivity of the reservoir. To quantify the dynamic response of the reservoir and related risks, a 4D reservoir/geomechanics simulation was conducted for Keshen Reservoir by following an integrated work flow. The work started from systematic laboratory fracture-conductivity tests performed with fractured cores to measure conductivity vs. confining stress for both natural fractures and hydraulic fractures (with proppant placed in the fractures of the core samples). Natural-fracture modeling was conducted to generate a discrete-fracture network (DFN) to delineate spatial distribution of the natural-fracture system. In addition, hydraulic-fracture modeling was conducted to delineate the geometry of the hydraulic-fracture system for the stimulated wells. Then, a 3D geomechanical model was constructed by integrating geological, petrophysical, and geomechanical data, and both the DFN and hydraulic-fracture system were incorporated into the 3D geomechanical model. A 4D reservoir/geomechanics simulation was conducted through coupling with a reservoir simulator to predict variations of stress and strain of rock matrix as well as natural fractures and hydraulic fractures during field production. At each study-well location, a near-wellbore model was extracted from the full-field model, and casing and cement were installed to evaluate well integrity during production. The 4D reservoir/geomechanics simulation revealed that there would be a large reduction of conductivity for both natural fractures and hydraulic fractures, and some fractures with certain dip/dip azimuth will be reactivated during the course of field production. The induced-stress change will also compromise well integrity for those poorly cemented wellbores. The field-development plan must consider all these risks to ensure sustainable long-term production. The paper presents a 4D coupled geomechanics/reservoir-simulation study applied to a high-pressure/high-temperature (HP/HT) naturally fractured reservoir, which has rarely been published previously. The study adapted several new techniques to quantify the mechanical response of both natural fractures and hydraulic fractures, such as using laboratory tests to measure stress sensitivity of natural fractures, integrating DFN and hydraulic-fracture systems into 4D geomechanics simulation, and evaluating well integrity on both the reservoir scale and the near-wellbore scale.
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Iftikhar, Javeria, Muhammad Nasir Saleem, Faiza Awais, Ayesha Naz, Adeel Tuasene, Zain Saleem e Khezran Qamar. "Frequency and Causes of Fracture of Acrylic Resin Complete Dentures in Edentulous patients". Pakistan Journal of Medical and Health Sciences 16, n. 7 (30 luglio 2022): 160–62. http://dx.doi.org/10.53350/pjmhs22167160.
Testo completoAbstract (sommario):
Background: The rehabilitation of edentulous patients requires acrylic resin complete dentures to fulfil their functional and esthetic needs. Fractures of dentures are one of the commonest complaints around the world. Aim: To evaluate the frequency of acrylic complete denture fractures among edentulous patients and find out their association with certain variables. Methodology: A cross sectional observational study was carried out in Prosthodontic department of Lahore Medical and Dental College, Lahore from 26th March 2020 to 26th September 2021. A total of 58 completely edentulous patients reported with fractured acrylic dentures were selected. Patients were evaluated both intra and extra orally to find out the cause and site of fracture. Various parameters namely, denture age, fracture sites, gender were statistically evaluated to find out their relationship with denture fracture. Results: Results showed that male patients; 56.9% were presenting more with fractured dentures than female; 43.10%. In males the midline denture fractures were most commonly seen 45.5%, whereas in females’ fracture at premolar area was commonly observed 28.0% however no statistical dependance between fractured dentures sites and gender was found. Denture fractures were most prevalent in mandibular arch 50% as compared to maxillary 39.7%. Mid line fracture was the commonest site observed in both maxillary 30.4% and mandibular arches 31.0%. Insignificant association between fracture sites and dental arches was seen. Maximum denture fractures were recorded in first 2 years of denture fabrication 55.2%. The most frequent cause of denture fracture was accidental falling 34.5%. Conclusion: The frequency of complete denture fracture is more in mandible as compared to maxilla and the main reason is patients’ negligence. The study also showed midline fracture of dentures to be the most frequent site of denture fracture. Keywords: Acrylic dentures, Complete dentures, Edentulism, Edentulous, Prosthesis, Tooth loss,
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Khurshid, Ilyas, Emad Walid AlShalabi, Hazim Al-Attar e Ahmed Khalifa AL-Neaimi. "Analysis of formation damage and fracture choking in hydraulically induced fractured reservoirs due to asphaltene deposition". Journal of Petroleum Exploration and Production Technology 10, n. 8 (22 maggio 2020): 3377–87. http://dx.doi.org/10.1007/s13202-020-00910-8.
Testo completoAbstract (sommario):
Abstract Hydraulically induced fractures provide a significant fraction of oil supply to the world from unconventional reservoirs due to their high permeability. However, these fractures might choke because of the deposition of organic and in-organic particles. Among organic particles, asphaltene deposition severely reduces reservoir permeability causing an exponential drop in production. In this work, a simulator is developed that predicts the performance of fractured reservoirs by solving the fluid flow governing equations for matrix and fractures. These flow equations were then incorporated with asphaltene deposition equations. Primarily, a numerical model is developed to predict the rate of asphaltene deposition and fracture choking in a radial geometry. It is found that asphaltene deposition could partially or completely choke fractures. Finally, the results are compared with the experimental data and determined various factors affecting fracture choking. From the detailed analysis, it is found that fracture choking is a few percent, but it increases with long production time. The sensitivity analysis was performed to investigate the effect of different influential parameters on permeability alteration of fractured reservoirs by asphaltene deposition. These parameters include fracture-to-matrix permeability ratio, production time, and asphaltene concentration. It is observed that, low fracture-to-matrix permeability ratio has a negligible effect on permeability of a reservoir. The developed model assumes negligible gravity and capillary forces. However, these forces might increase fracture choking in unconventional fractured reservoirs.
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Dang, Hong-Lam. "Modeling the Effect of Intersected Fractures on Oil Production Rate of Fractured Reservoirs by Embedded Fracture Continuum Approach". Modelling and Simulation in Engineering 2019 (2 luglio 2019): 1–10. http://dx.doi.org/10.1155/2019/4034860.
Testo completoAbstract (sommario):
The homogenization of matrix and short fractures is one of the conventional approaches to deal with a plenty of fractures in different scales. However, the accuracy of this approach is still a question when long fractures and short fractures are distributed in the homogenized model. This paper describes a new hybrid method in which the long fractures will be modeled explicitly by the embedded fracture continuum approach and short fractures are considered through the homogenized technique. The author used this hybrid method to demonstrate the effect of fractures which are intersected to the well on the oil production rate as well as the elapsed time of a fractured reservoir in a depletion process. The advantages of the new hybrid method are easy assembling of numerous fractures into the model and incorporation of the complex fracture behaviour into the model.
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Zheng, Hanwen, Zhansong Zhang, Jianhong Guo, Sinan Fang e Can Wang. "Numerical Simulation Study on the Influence of Cracks in a Full-Size Core on the Resistivity Measurement Response". Energies 17, n. 6 (13 marzo 2024): 1386. http://dx.doi.org/10.3390/en17061386.
Testo completoAbstract (sommario):
The development of fractured oil fields poses a formidable challenge due to the intricate nature of fracture development and distribution. Fractures profoundly impact core resistivity, making it crucial to investigate the mechanism behind the resistivity response change in fracture cores. In this study, we employed the theory of a stable current field to perform a numerical simulation of the resistivity response of single-fracture and complex-fracture granite cores, using a full-size granite core with cracks as the model. We considered multiple parameters of the fracture itself and the formation to explore the resistivity response change mechanism of the fracture core. Our findings indicate that, in the case of a core with a single fracture, the angle, width, and length of the fracture (fracture occurrence) significantly affect core resistivity. When two fractures run parallel for a core with complex fractures, the change law of core resistivity is similar to that of a single fracture. However, if two fractures intersect, the relative position of the two fractures becomes a significant factor in addition to the width and length of the fracture. Interestingly, a 90° difference exists between the change law of core resistivity and the change law of the resistivity logging response. Furthermore, the core resistivity is affected by matrix resistivity and the resistivity of the mud filtrate, which emphasizes the need to calibrate the fracture dip angle calculated using dual laterolog resistivity with actual core data or special logging data in reservoirs with different geological backgrounds. In the face of multiple fractures, the dual laterolog method has multiple solutions. Our work provides a reference and theoretical basis for interpreting oil and gas in fractured reservoirs based on logging data and holds significant engineering guiding significance.
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Wong, Liam H., Lara C. Atwater e Alden E. Wyland. "Impact of Obesity on Severity of Ankle Fracture". Foot & Ankle Orthopaedics 7, n. 4 (ottobre 2022): 2473011421S0100. http://dx.doi.org/10.1177/2473011421s01005.
Testo completoAbstract (sommario):
Category: Trauma; Ankle Introduction/Purpose: Ankle fractures are one of the most common types of foot and ankle trauma requiring surgery. Prior studies have investigated the association between obesity and ankle fracture on a general level, but not all studies have broken down the data by ankle fracture pattern subtypes. The aim of this study was to investigate the association between obesity and severity of ankle fractures, as classified by single malleolar (isolated fibular, posterior malleolar or medial malleolar), bimalleolar, trimalleolar and pilon subtypes. Methods: We retrospectively investigated the patient charts of 1,326 treated ankle fractures from 2011 to 2021 at a level 1 trauma center as identified by CPT codes. Collected data included age, diagnosis, BMI (obese > 30 kg/ m2), and vitamin D. For this study, we excluded patients who did not have a fracture of a malleoli or a pilon fracture (n=129). Severity of fracture was determined by number of malleoli fractured with the addition of pilon fracture as the most severe. Inferential statistics were performed using ANOVA and chi-squared tests. Results: Of 1,197 patients with an operatively managed ankle fracture (median age 28.7 years), 516 (43.2%) were obese. There were 434 (36.3%) unimalleolar fractures, 396 (33.1%) bimalleolar fractures, 294 (24.6%) trimalleolar fractures, and 73 (6.1%) pilon fractures. Obesity represented 39.4% (n=171) of unimalleolar fractures, 42.7% (n=169) of bimalleolar fractures, 50.0% (n=147) of trimalleolar fractures, and 39.7% (n=29) of pilon fractures (P<0.037). There were 273 (62.9%) lateral malleolar fractures, 127 (29.3%) medial malleolar fractures, and 34 (7.8%) posterior malleolar fractures. Obesity represented 45.4% (n=124) of lateral malleolar fractures, 29.1% (n=37) of medial malleolar fractures, and 29.4% (n=10) of posterior malleolar fractures (P<0.004). Obese patients had a higher probability of a trimalleolar fracture compared to a unimalleolar (OR 1.54; 95% CI, 1.14-2.07; P=0.005) as well as having a lateral malleolar fracture compared to a medial malleolar (OR 2.02; 95% CI, 1.29-3.18; P=0.002). Conclusion: This review of all operatively treated ankle fractures at a level 1, academic trauma center suggests that obesity is associated with increasing severity of ankle fracture patterns, with the exception of pilon fractures. Obese patients have a higher probability of having a trimalleolar fracture than a unimalleolar fracture. Obese patients are also more likely to have a lateral malleolar fracture compared to a medial malleolar fracture. Patients and clinicians should be aware of this higher risk of trimalleolar fractures as these fractures are commonly associated with worse outcomes and a higher probability of developing osteoarthritis.