Fracture Size Research Articles

Influence of posterior malleolar fragment morphology on the outcomes of trimalleolar fractures: A systematic review and meta-analysis

BackgroundTrimalleolar fractures are generally considered to have inferior outcomes among ankle injuries. Historically, emphasis was placed on the size of the posterior malleolar fracture (PMF) to guide surgical decision-making and predict outcomes. Recent studies have suggested that the morphology of the PMF fragment is more important than its size. The aim of this systematic review was to determine if the outcomes of trimalleolar fractures depend on the morphology of the PMF as per the Haraguchi classification system after surgical fixation. MethodsA systematic literature search was conducted in the electronic databases of PubMed, Embase, Scopus, and Ovid. Title and abstracts were screened, and data from eligible studies were extracted. Meta-regression and pooled analysis was performed using appropriate computer software. Results11 studies with 597 patients were included in the final analysis. Pooled mean AOFAS score was 87.43 (95% CI 84.24–90.62) after a mean follow-up of 31.6 months. Univariate and multivariate meta-regression analysis demonstrated that as the percentage of Haraguchi type 1 patients increased, there was a statistically significant improvement in outcome scores. A similar trend was noted for Haraguchi type 3 fractures, and a reverse trend was observed for Haraguchi type 2 injuries, although neither were statistically significant. ConclusionOur review suggests that the outcomes of trimalleolar fractures after surgical fixation may depend on the morphology of the PMF, with Haraguchi type 1 fractures having overall superior functional outcomes than Haraguchi type 2 and 3 injuries. Future studies need to done to conclusively prove or refute these findings.

Research on the Characteristics of Infrared Radiation and Energy Evolution Law of Red Sandstone with Different Porosity during Uniaxial Compression

Infrared radiation thermal imaging technology is proposed for rock mechanics tests. Through the infrared radiation temperature and stress–strain curves of sandstone with different porosity during the process of uniaxial compression loading obtained by an infrared camera and uniaxial compression testing machine, the characteristics of infrared radiation on sandstone are systematically analyzed during uniaxial compression loading. The results show that: (1) The strength of sandstone decreases with the increase of porosity, the infrared thermography of sandstone has obvious characteristics of stage evolution and is closely related to the deformation and failure stage of rock in the process of uniaxial compression; (2) During the rock failure process, infrared thermography is differentiated, and the high-temperature radiation zone can reflect the location, size and shape of rock fractures; (3) During the uniaxial compression loading process, the evolution law of the average infrared radiation temperature (AIRT) is closely related to the porosity and uniaxial compressive of the rock, and it is possible to invert all processes of rock failure. The research results demonstrate that the technique of infrared thermal imaging can be applied to rock mechanics tests, and the evolution law of the infrared radiation characteristics can provide a reference for stability analysis of the underground rock engineering.

A design method for determining fracture toughness and tensile strength pertinent to concrete sieving curve

The aggregate particle gradation of concrete, which is generally characterized by a sieving curve, is a critical factor affecting the formation of the core stress skeleton of concrete specimens. In this paper, a fracture size and boundary effect model that can describe the effect of aggregate gradation on crack propagation at the micro-level in concrete is developed. The critical points on the aggregate sieving curve are selected as the characteristic values of aggregate particles. The individualized calculation method of the fictitious crack growth length under peak load is provided, while the corresponding design application method of the simplified value of the fictitious crack growth length is given. The micro-level explains the physical nature of the discontinuous and jumping expansion of concrete cracks caused by the different aggregate particle gradations. The formula of the novelty design method can link the aggregate particle gradation at the micro-level with the macroscopic fracture and strength parameters. Further, a simplified two-point method to determine the concrete fracture and strength parameters simultaneously by using only two different specimens has been proposed. The proposed model and design method are not limited to the type of specimens. The concrete parameters and structural failure prediction analysis can be carried out by using notched, un-notched, geometrically similar, as well as non-geometrically similar specimens.

Holding your shape: Controlled tip fracture experiments on cast porcelain points

The development of projectile technology was a fundamental step in the transition from scavenging to hunting, providing hunters with more reliable access to meat, enabling killing at greater distances and a potential broadening of the human niche. Understanding when and where projectile innovations occurred remains a challenge, as organic components of projectile technology seldom preserve. Consequently, archaeologists have explored tip fractures as a potential means of identifying the speed of projectile impacts and thus the likely weapon systems employed in the past. This paper introduces a novel approach to experimental projectile fractures, employing near-identical vitrified porcelain points to better understand the variables affecting formation, type and length of so-called ‘diagnostic impact fractures’ (DIFs). Using the largest sample of its kind to date (n = 570), we compare DIF type and length for thrusted spear, simple stone tipped projectiles (hand thrown) and complex projectile weapons (spearthrower/dart and bow/arrow) to identify the degree of overlap in the type and size of impact fractures created by each type of weapon. Through statistical comparison of porcelain and flint points, and controlled crossbow and hand delivery methods, we show that porcelain points are an ideal analogue for flint points in controlled ballistic experiments to assist in developing a more robust understanding of the formation of impact fractures and the use of past weapon systems.

Effect of Neutron Irradiation on the Critical Event Size of Cleavage Fracture of the Chinese A508-3 Steel

In order to analyze the influence of neutron irradiation on the critical event of cleavage fracture for the Chinese A508-3 (RPV) steel, the fracture morphology, microstructure and grain size of the irradiated specimens are observed and analyzed by optical microscope (OM) and scanning electron microscope (SEM). The results show that with the increase of neutron doses, the fracture mode of Chinese RPV steel material changes gradually from ductile fracture to ductile-brittle mixed fracture transformation. The brittle part for fracture mode of ductile-brittle fracture is cleavage fracture, and the non-metallic inclusions, microstructure and grain size grades are not significantly different from those of the specimens without cleavage fracture. In the same material, with increasing of neutron doses, the critical event size of the cleavage fracture will be reduced, and the percentage of the grain that satisfies the grain size of the cleavage critical event will increase correspondingly, resulting in an increase of the probability of cleavage fracture of the material. The fine grain with uniform distribution can improve partly the fracture toughness of the material and withstand higher neutron doses under the same conditions.

Numerical Investigation on Interference of Multiple Hydraulic Fractures in Layered Formation

Staged treatment in vertical wells is extensively applied in layered formation to obtain commercial exploitation of hydrocarbon resources. Large-sized heterogeneities always exist between multiple hydraulic fractures in different layers. To reveal the interference of multiple hydraulic fractures in layered formation, a series of numerical investigations were conducted based on the cohesive zone finite element method. The results show that the sole stress interference is too small to exert an effective impact on adjacent pay zones, which is quite different from those in horizontal wells. The flow distribution in one pay zone can reach 56.2%, which is more than five times the magnitude of the least 10.5% during the fracturing in three pay zones. The fracture size heterogeneities are mainly caused by the interference of the fluid flow into multiple perforation tunnels in different pay zones. To further clarify how the flow distribution in the pay zones is affected, five related factors, including perforating thickness, pay zone thickness, rock permeability, minimum horizontal stress of the pay zone, and rock strength, are analyzed. The results show that it is through the manner of flow distribution adjustment in each pay zone that the five factors affect the fracture size. This study is of critical importance to clarify how the multiple hydraulic fractures from vertical wells interfere in layered formation and explain why the hydraulic fractures we get in the field are far away from what we want ideally.

Direct electromagnetic coupling to determine diagnostic bone fracture stiffness.

BackgroundRapid prediction of adverse bone fracture healing outcome (e.g., nonunion and/or delayed union) is essential to advise adjunct therapies to reduce patient suffering and improving healing outcome. Radiographic diagnostic methods remain ineffective during early healing, resulting in average nonunion diagnosis times surpassing six months. To address this clinical deficit, we developed a novel diagnostic device to predict fracture healing outcome by noninvasive telemetric measurements of fracture bending stiffness. This study evaluated the hypothesis that our diagnostic antenna system is capable of accurately measuring temporal fracture healing stiffness, and advises the utility of this data for expedited prediction of healing outcomes during early (≤3 weeks) fracture recovery.MethodsFracture repair was simulated, in reverse chronology, by progressively destabilizing cadaveric ovine metatarsals (n=8) stabilized via locking plate fixation. Bending stiffness of each fracture state were predicted using a novel direct electromagnetic coupling diagnostic system, and results were compared to values from material testing (MT) methods. While direct calculation of fracture stiffness in a simplistic cadaver model is possible, comparable analysis of the innumerable permutations of fracture and treatment type is not feasible. Thus, clinical feasibility of direct electromagnetic coupling was explored by parametric finite element (FE) analyses (n=1,632 simulations). Implant mechanics were simulated throughout the course of healing for cases with variations to fracture size, implant type, implant structure, and implant material.ResultsFor all fracture states, stiffness values predicted by the direct electromagnetic coupling system were not significantly different than those quantified by in vitro MT methods [P=0.587, P=0.985, P=0.975; for comparing intact, destabilized, and fully fractured (FF) states; respectively]. In comparable models, the total implant deflection reduction (from FF to intact states) was less than 10% different between direct electromagnetic coupling measurements (82.2 µm) and FE predictions (74.7 µm). For all treatment parameters, FE analyses predicted nonlinear reduction in bending induced implant midspan deflections for increasing callus stiffness.ConclusionsThis technology demonstrates potential as a noninvasive clinical tool to accurately quantify healing fracture stiffness to augment and expedite healing outcome predictions made using radiographic imaging.

Assessment of applicability of preformed particle gels for Perm region oil fields

The application of preformed particle gels (PPG) in Russian oil fields is very limited. In this research the authors tried to find tools for primary screening of oil wells candidates for PPG application. For a fractured reservoir, the Warren-Rutt method was considered for estimating fracture sizes in injected oil wells. Taking into account the mechanical properties of the developed PPG, a powder fraction is recommended for starting treatment of oil wells. An express method for assessing the pressure index (PI) was considered for the primary selection of well candidates. PI provides information on reservoir heterogeneity. Using this method, the most promising candidates for the implementation of PPG technology were selected.

Site-scale bedrock fracture modeling of a spent fuel reprocessing site based on borehole group in Northwest, China

A spent fuel reprocessing site (SFRS) is under constructions on granitic beds in Northwest China. To safely manage the potential migration of nuclides, it is critical to accurately characterize the natural fracture system in the bedrock and accurately predict the variability in the geological environment. However, a workflow for site-scale discrete fracture network (DFN) modeling has not been fully established in China. Therefore, a new site-scale DFN modeling framework utilizing borehole core data as constraints was proposed for fractured biotite granite within several kilometers of the SFRS. This method quantified the P10 values of 227 pre-implemented engineering cores and obtained local P32 values using a conversion factor. Based on geostatistics, this method realized the fast estimation of global P32, a key parameter in DFN modeling, at minimal cost under a scenario with extremely limited outcrop data. Further, 1933 fractures obtained from extensive field mapping supplemented the fracture orientation and size information. By integrating the modeling parameters into the proposed framework, a site-scale DFN model database was successfully established. Finally, an acceptable site-scale DFN model was obtained from the database by comparing the measured and simulated P10 values, which demonstrated the effectiveness and feasibility of this method. Compared with the traditional DFN modeling, the proposed framework captured the heterogeneity of the fracture spatial intensity. The modeling results revealed the fracture distribution in the SFRS, and illustrated the broad potential applicability of this modeling framework in the field of geological engineering. This study provides a new insight for site-scale DFN modeling in China.

A Novel Continuous Fracture Network Model: Formation Mechanism, Numerical Simulation, and Field Application

After a shale gas reservoir is fractured, hydraulic fractures interweave with natural fractures to form a fracture network. Numerical simulation based on the continuous fracture network model is a relatively economical and convenient method to predict fracture network morphology and size in the field application. However, some important factors, such as fracture height variation and filtration loss, have not been considered in the past continuous fracture network models. Therefore, this paper is aimed at establishing a novel continuous fracture network model to improve simulation accuracy. Firstly, this paper established a method to judge whether natural fractures develop or not. Then, a novel continuous fracture network model considering fracture height variation and asymmetry, filtration loss, fluid flow, and other key factors was established, and the forward algorithm and inverse algorithm of the model were proposed. At last, this model was applied in a field case to verify accuracy, and the average accuracy is more than 90%. Compared with the traditional Meyer software, the average error of prediction was reduced by 7.86%.

Dynamically Evaluating the Performance of Naturally Occurring Additives to Control Lost Circulation: On the Effect of Lost Circulation Material Type, Particle-Size Distribution, and Fracture Width

Summary Lost circulation is one of the most challenging problems during drilling of oil and gas wells. This issue leads to significant loss of drilling fluid, increase of nonproductive time as well as dictating additional costs to drilling companies. Lost circulation may also lead to other consequences, including stuck pipe, poor hole cleaning, and well control issues. How to efficiently control lost circulation have been traditionally depending on the type of the used lost circulation material (LCM). Injection of commonly available materials (without any further process on their chemical properties) into the thief zone is a common method of lost circulation control. These nonmodified materials are named as conventional LCMs against the unconventional LCMs which are designed/produced just for fluid lost control. The objective of this paper is to comparatively investigate the performance of cane, oak shell, wheat, and mica as LCM of water-based drilling fluid exposed to fractured formations. These materials were chosen because of their low cost, easy access, and compatibility with the environment. The sealing efficiency of these materials was assessed at different particle-size distributions (PSDs) for proper treatment of loss circulation. To do so, an experimental setup containing a cell with adjustable fracture size was designed. Among the LCM formulations made of each of the materials, oak shell formulations are better than the others, followed by mica and cane blends, respectively. The results reveal that combining the materials together is a better treatment than the separate use of them. As it will be seen in detail later, high diversity in particle size (broad PSD) causes more efficient control of fluid loss. Also, to reduce the dependency of sealing ability of LCM formulation on fracture size, mixing of the materials with different particle sizes and shapes is recommended.

Examining the protective role of the posterior elements of the spine against endplate fractures in a porcine model.

Previous studies have shown that the posterior elements/facet joints provide strength to the overall functional spine unit (FSU) by taking 3-25% of vertical compressive load off the intervertebral disc (IVD). However, little is known regarding whether this offloading has a protective effect against endplate fracture. Therefore, the purpose of this study was to investigate if the posterior elements provide a protective role to the endplate in porcine cervical spines under fracture-inducing conditions. Twenty-two cervical porcine FSUs (C5/6 level) were randomized into two groups: 1) a control group which had their posterior elements left intact (n = 11); 2) an experimental group which had the posterior elements removed (n = 11). Each FSU underwent a previously reported rapid IVD pressurization protocol in order to create endplate fractures. Briefly, hydraulic fluid was rapidly injected into the IVD via a standard inflation needle inserted through the anterior annulus which was connected to a hydraulic pump and pressure transducer. Post pressurization, each FSU was dissected to determine the presence and size of endplate fracture. Peak pressurization and rate of pressurization were not found to differ between intact and cut specimens (p = 0.313 and 0.101, respectively). In contrast, significantly, more cut FSUs sustained an endplate fracture (11/11) compared to intact FSUs (5/11); p = 0.012. Further, cut FSUs resulted in a fracture area 1.91 times greater in size compared to the fractures seen in the intact FSUs (p = 0.011). Therefore, posterior elements appear to decrease the risk and severity of endplate fracture.

In situ investigation of the fracture of primary carbides and its mechanism in M50 steel

The tensile crack initiation and propagation of M50 bearing steel were investigated. It is found that the primary carbides were fractured during the tensile test by in situ SEM, while decohesion of the carbide/matrix interface was hardly observed. In order to capture the initial tensile crack, quasi-in situ X-ray microtomography was performed, indicating that the earliest crack was formed from the broken interior carbides. This indicates that multiple cracks already existed in the matrix when they were observed on the sample surface. Electron backscattered diffraction (EBSD) and the finite element method (FEM) were applied to analyze the fracture behavior of carbide particles. The fracture of carbide particle is produced by the incompatible deformation between the matrix and carbides. The frequency of carbide fracture was found to be related with its fracture strength, size and shape. M 2 C carbide fracture was more easily broken than the MC carbide during tensile test. In addition, the long axis of most M 2 C carbides is approximately parallel to its (0001) plane and normal to tensile stress, leading to cracking more easily. Finally, a suggestion of adding pre-deformation is proposed to make M 2 C carbides broken sufficiently and further refine the primary carbides. • X-ray microtomography is applied to analyze the evolution of primary carbides. • Incompatible deformation between the matrix and particles leads to carbide fracture. • M 2 C carbide is more easily broken than MC carbide. • Pre-deformation before diffusion annealing should be applied to refine carbides.

A Comparison of Linear Solvers for Resolving Flow in Three‐Dimensional Discrete Fracture Networks

AbstractWe compare various methods for resolving steady flow within three‐dimensional discrete fracture networks, including direct methods, Krylov subspace methods with and without preconditioning, and multi‐grid methods. We compared the performance of the methods based on compute times and scaling of the solution as a function of the number of grid nodes and log‐variance of the hydraulic aperture. The methods are applied to three test cases: (a) variable density of networks with a truncated power‐law distribution of fracture lengths, (b) a fixed network composed of monodisperse fracture sizes but varied permeability/aperture heterogeneity, (c) and a network based on field site in Nevada, US. We chose these cases to allow us to study the impact of the mesh size and flow properties, as well as to demonstrate our conclusions on a large‐scale, realistic problem (more than 40 million mesh nodes). A direct solution using Cholesky factorization outperformed other methods for every example but was closely followed in performance by some algebraic multigrid (AMG) preconditioned Krylov subspace methods. Among the Krylov methods, conjugate gradients (CG) with an AMG preconditioner performs the best. Generally, Cholesky factorization is recommended, but CG with an AMG preconditioner may be suitable for very large problems beyond 40 million nodes where the entire linear system cannot reside in memory.

Application of the effective diameters of porous media to the non-Darcy flow analyses

Non-Darcy flows are a vital event leading to the inaccuracy in flow performance evaluation, particularly in the fractured wells in shale gas and tight oil deposits. The internal flow commonly indicates high flow rates at the early period of production, owing to the large geometric size of hydraulic fracture and high porosity in proppant packs. After that, the production flow rate decays steeply until the Darcy flow regime is attained. Therefore, accurate porous flow analyses from the Darcy to Forchheimer and then turbulent flow regimes are essential for optimal facility designs and economic productions in the unconventional deposits. The Comiti capillary model is recognised as the leading non-Darcy flow correlation for simple packed beds comprising mono-size grains. However, in actual hydraulic fractures, various types of proppants are used simultaneously and generally combined with numerous soil grains of different sizes and shapes. In this study, the Comiti model is modified by incorporating the effective diameters of the porous media and then examined for mixed complex multi-size packs. Subsequently, a novel type of non-Darcy flow equation is presented according to the logarithmic turbulent friction factor based on the physical variables determined only in the Darcy flow regime. The new equation presents accurate results for all the types of proppant packs under wide porosity and permeability ranges. The generalised non-Darcy flow correlation, which can be extensively employed from the Darcy to non-Darcy flow analyses, particularly beyond the Forchheimer regime, is presented for the accurate flow evaluation of the fractured reservoirs.

Detecting the ground-dependent structural damages in a historic mosque by employing GPR

This study aims to employ one of the most significant geophysical methods, known as the ground penetrating radar (GPR) method, in the determination of reasons for the underground cavities, the size of deformations and fractures in the ground and structure, the geometric behavior patterns, and the soil-structure interaction and changes in a historic structure. In addition to the instrumental examination, an observational investigation of the current situation of the mosque was also carried out. İskender Pasha Mosque, which is a rare mosque having a tabhane (guest house), is one of the important historical mosques regarded as built-in Mimar Sinan style in Diyarbakır, Turkey in 1552. The instrumental examination part of the study was conducted totally in 13 different regions of the mosque and its courtyard. Within this scope, 8 GPR measurements were taken on the ground of the mosque and its immediate environment and 5 GPR measurements were taken on the walls of the mosque. The GPR measurements indicated that there are serious subsidence anomalies under the mosque and its courtyard. Besides, there is a water table under the portico of the mosque which may lead to big problems in the future. In addition, observationally detected structural deteriorations were supported by geophysical GPR measurements. It was revealed that problems dealing with the leveling irregularities on the floor of the harim, portico, and courtyard are directly related to the anomalies under the ground. Moreover, it was achieved from both instrumental and observational investigations that the anomalies under the ground are directly the reasons for the anomalies in the walls of the mosque. GPR results demonstrated that this technique can be used effectively to determine anomalies in both the carrier system of the historic structures and the ground under the historic structures without any damage.

Application of geomechanics modeling in the study of fluid loss mechanism of fractured reservoirs in Bohai Bay, China

Drilling fluid loss in fractured formations is still an engineering problem to be solved. This work establishes an analysis method for fluid loss in fractured formation based on geomechanics modeling. The method is applied in the Bohai B oilfield in Bohai Bay, China. Three-dimensional fracture intensity and lost circulation pressure of the reservoir are established. Meanwhile, the influence of fracture dip angle and fracture width on fluid loss and the performance of onsite lost circulation materials are investigated. The results show that the reservoir of Bohai B oilfield has extensively developed fractures and the safety mud density window is very narrow in the fracture-development areas. The areas with fracture development are strongly correlated to the zones of high fluid loss risk. In addition to fracture size, the magnitude of fluid loss is also closely related to the dip angle of the fractures, and a higher fracture dip aggravates fluid loss. The proposed method can effectively characterize the development of fractures, evaluate the impact of fracture characteristics on fluid loss, and identify locations with a high risk of fluid loss.

Fully 3D Simulation of Hydraulic Fracture Propagation in Naturally Fractured Reservoirs Using Displacement Discontinuity Method

Summary The shape, size, and orientation of natural fractures significantly impact the geometry of hydraulic fractures in unconventional reservoirs, such as shale gas/oil, tight gas, and enhanced geothermal system. The behaviors after the hydraulic fracture encounters natural fractures have been summarized as crossing, diverting, step over, and stopping based on a great number of numerical and experimental analysis with plain strain assumptions. However, under practical situations, the geometries of natural and hydraulic fractures are much more complex than the vertical and rectangular shape assumed by 2D models. The experimental studies on the role of height and inclination of natural fractures have revealed some other phenomena (e.g., bypassing process that the fluid-driven hydraulic fracture propagates up the back side of the natural fracture), which are unable to be captured in 2D. To better describe the intersection behaviors among different kind of fractures, a fully 3D model based on the displacement discontinuity method (DDM) is developed on top of our previous models, which only considered the propagation of hydraulic fractures. A novel crossing criterion to judge whether the hydraulic fracture will cross the cemented natural fracture in 3D is proposed. The successive node snapping scheme is adopted to construct conforming meshes for the evolving intersected curves between hydraulic and natural fracture surfaces, which only alters the location of a small fraction of nodes without changing the nodal connectivity. With this model, the evolution of fracture geometry after the hydraulic fracture intersects with the natural fractures of different toughness, size, orientation, and number is investigated. Because an extra dimension is considered, the fractures are allowed to propagate in more directions, resulting in a series of complex fracture geometries. The dynamic grid evolution method proposed in this work can promote the development of DDM in modeling fully 3D fracture networks in naturally fractured reservoirs.

Anisotropic Effective Elastic Properties for Multi-Dimensional Fractured Models

The size, distribution, and orientation of fractures are generally multiscale and multi-dimensional in nature, leading to complex anisotropic characteristics. Theoretical or semi-analytical methods to determine the effective elastic properties depend on several assumptions, including the absence of the stress interaction and idealized fractures. On the basis of finite-element models, we conduct numerical oscillatory relaxation tests for determining the effective elastic properties of fractured rocks. The numerical approach for calculating equivalent stiffness tensors in two-dimensions is compared to the theoretical models for different fracture densities. Due to fracture interactions at high fracture densities, the suggested model makes a physical prediction. The effective elastic properties obtained from the application to a real fractured model, established from an outcrop, obviously disperse at different frequencies, which can be used to investigate fracture interactions and dynamic stress disturbances. The algorithm is extended to three-dimensional cases and also validated by using conventional effective medium theories. It is found that the fracture density obviously impacts the effective anisotropy properties, and the proposed method gives a reasonable prediction for high-fracture density. This work is significant because it enables the calculation of effective elastic properties of multi-dimensional fractured models and the fracture interaction mechanism.

Insights into the mechanical stratigraphy and vertical fracture patterns in tight oil sandstones: The Upper Triassic Yanchang Formation in the eastern Ordos Basin, China

Vertical fracture patterns are mapped in the outcrops to analyze the impact of mechanical stratigraphy on vertical fractures in the relatively undeformed Upper Triassic tight oil sandstones of the Yanchang Formation along Yanhe River in the east Ordos Basin, China. The relationship between natural fractures and different bounding interfaces are analyzed based on rock relative strength measurement by N-type Schmidt Hammer, fracture and facies description in the outcrops. According to the probability of the bounding interface terminating natural fractures being more than 20%, seven types of mechanical interfaces terminating fracture longitudinal propagation are identified, namely 1) the interface of laminae-set or laminae co-sets, 2) bedding surface interface, 3) accretionary interface, 4) mudstone interbed, 5) mudstone barrier, 6) calcareous barrier and 7) depositional scour interface. According to fracture sizes and the mechanical interfaces which constrain fracture propagation, the vertical fractures are divided into micro-scale, small-scale, meso-scale and macro-scale ones. Three possible vertical fracture patterns in various sedimentary microfacies of the shallow water delta deposits are discussed based on field outcrop observation, the restriction capacities of different mechanical interfaces and the temporally changing tectonic stress. Finally, the application of vertical fracture patterns for subsurface fracture prediction is carried out in the Ansai Oilfield in the eastern Ordos Basin, China. The predicted fractures in wells are consistent with the fractures obtained from cores and conventional logs. This study links sedimentary stratigraphy, mechanical stratigraphy and natural fractures in the tight oil sandstones within a relatively undeformed setting, meanwhile unravels the vertical fracture patterns in different sedimentary microfacies of the shallow water delta deposits in the study area. The results will thus guide subsurface fracture prediction between wells in the tight oil sandstones of the eastern Ordos Basin.