Cracks In Shale Research Articles

Micro-failure behaviors of mineral crystals in reservoir rocks impacted by abrasive water jet

Abrasive water jet (AWJ) has been widely used in the development of reservoir resources. In the relevant literature, the mechanism of perforation formation by AWJ impacting rocks in different reservoirs, the effect of rock genesis and mineral species during the material removal process, and the location of crack propagation remain unclear, and there is no comprehensive study that investigates the micro failure behaviors of mineral crystals in the rocks. As a result, in this study, we use AWJ to impact reservoir rocks (granite, sandstone, limestone, and shale), the rock damage and the macro morphology of perforations are characterized by Computed Tomography (CT); then the surface features of perforations are obtained by a 3D morphology scanner and the Joint Roughness Coefficient (JRC) is calculated; finally, the micro characteristics of perforations are analyzed by using a polarizing microscope and scanning electron microscope (SEM). The results show that for all four rock types, the perforation wall formed by AWJ presents relatively smooth (JRC: granite-8.2, sandstone-5.9, limestone-8.3 and shale-11.6) and rough (JRC: granite-13.1, sandstone-12.6, limestone-17.5 and shale-18.5) surfaces, with the location of cracks typically developing around the latter. Sedimentary reservoirs being more susceptible to generate cracks along particle cementation boundaries. Moreover, damage and cracks in shale are more likely to extend along the bedding planes. The results clarified the perforation formation mechanism and the crack development areas of AWJ impacting different reservoir rocks.

Study on the Damage and Failure Process of Prefabricated Hole-Fracture Combination Defects in Shale

The rock formations in oil and gas reservoirs are predominantly composed of laminated shale, which contains various defects such as pores and fractures. These defects have a significant impact on the stability of wellbore walls. As a result, this study utilized rock samples from a specific oil and gas reservoir and introduced pre-existing pore and fracture defects within them. Uniaxial compression tests were conducted on rock specimens with varying angles between the fractures and the bedding planes. The study involved measuring and analyzing the impact of pre-existing defect morphology on shale’s mechanical properties. Additionally, through the use of digital image correlation (DIC) technology, a comprehensive strain field map was obtained, depicting the initiation, propagation, and ultimate failure of surface cracks in shale under loading conditions. This allowed for both qualitative and quantitative analysis of the connection between shale’s damage and failure processes and the evolution of strain fields. Ultimately, this research provides a theoretical basis for wellbore stability and the development of shale oil and gas fields. Conclusions drawn from the study are as follows. With an increase in fracture angle, the rock’s elastic modulus gradually increases, and both compressive strength and strain exhibit a pattern of higher values on both ends and lower values in the middle. When the fracture angle is less than 30°, significant stress concentration occurs at the tip of the fracture. When the angle exceeds 60°, stress concentration around pores dominates. In the range of 30° to 60°, there is a combined stress concentration around both pores and fractures, significantly reducing rock stability. Crack propagation is influenced by bedding planes and exhibits varying degrees of ductility, ultimately resulting in a tension-shear mixed failure. When fractures are parallel to bedding planes (angle = 0°), defects are symmetrically distributed, and stress concentration at the fracture tip dominates, leading to crack initiation from the fracture tip and eventually forming an “H”-shaped tensile failure. When fractures are perpendicular to bedding planes (angle = 90°), stress concentration around pores is greater than at the fracture tip, causing cracks to initiate around pores and eventually collapsing on one side of the fracture.

Impact of supercritical carbon dioxide on the frictional strength of and the transport through thin cracks in shale

Understanding the mechanical and transport behavior of thin (i.e. small aperture) cracks slipping under supercritical carbon dioxide (sc-CO2) conditions is essential to evaluate the integrity of sealing formations with buoyant sc-CO2 below and the success of waterless fracturing. The two major items of interest in this work are frictional strength and permeability change of the crack. We used a triaxial cell that permits in situ visualization to conduct and monitor slippage along the faces of narrow cracks subjected to triaxial stresses. Such cracks are analogs to small geological faults. We tested carbonate-rich, 1-inch diameter Wolfcamp shale samples that are saw cut 30° to vertical to create a thin crack. Friction coefficients ranged from about 0.6 to 0.8 consistent with expectations for brittle rocks. The sc-CO2 generally did not alter friction coefficient over the time scale of experiments. From a transport perspective, saturating cracks with sc-CO2 substantially decreased permeability of the crack by 26%–52%, while slip resulted in a variety of permeability responses. Overall, the combined impact of sc-CO2 saturation and slip reduced fault permeability for all tests. Our observations support the notion that the sealing capacity of some caprocks improves when saturated with sc-CO2 and that some slip of small fractures is not necessarily detrimental to caprock integrity.

Numerical Heat Transfer Simulation of Oil Shale Large-Size Downhole Heater

Downhole heaters are critical for effectively achieving in situ oil shale cracking. In this study, we simulate the heat transfer performance of a large-scale helical baffle downhole heater under various operational conditions. The findings indicate that at 160 m3/h and 6 kW the outlet temperature can reach 280 °C. Controlling heating power or increasing the injected gas flow effectively mitigates heat accumulation on the heating rod’s surface. The outlet temperature curve exhibits two phases. Simultaneously, a balance in energy exchange between the injected gas and heating power occurs, mitigating high-temperature hotspots. Consequently, the outlet temperature cannot attain the theoretical maximum temperature, referred to as the actual maximum temperature. Employing h/∆p13 as the indicator to evaluate heat transfer performance, optimal performance occurs at 100 m3/h. Heat transfer performance at 200 m3/h is significantly impacted by heating power, with the former being approximately 6% superior to the latter. Additionally, heat transfer performance is most stable below 160 m3/h. The gas heating process is categorized into three stages based on temperature distribution characteristics within the heater: rapid warming, stable warming, and excessive heating. The simulation findings suggest that the large-size heater can inject a higher flow rate of heat-carrying gas into the subsurface, enabling efficient oil shale in situ cracking.

Triple-phase-field modeling and simulation for mixed-mode fracture of bedded shale

Comprehending the intricate mechanics and fracture characteristics of shale holds significant importance in the realm of controlling the reconstruction of shale gas reservoirs. It is noteworthy that shale typically exhibits a distinctive bedding structure which sets it apart from other geological formations. Previously, single-mode cracks in shale have been widely studied by former researchers. However, its matrix and bedding may undergo various fracture modes under loading due to the bedded structure. To effectively capture the mixed-mode fracture behavior observed, a triple-phase-field model is proposed in this paper. Three phase-field variables are introduced herein to track pure-tension, tensile-shear, and compressive-shear cracks in the matrix and bedding, respectively. The energetic driving forces governing the propagation of pure-tension and tensile-shear cracks are formulated through the spectrum decomposition of positive strain tensor with its volumetric and deviatoric components; while the energetic driving force that propels the progression of compressive-shear cracks is derived by employing the Mohr-Coulomb criterion within the context of the negative strain tensor. For the bedding plane, lower-dimensional interfacial elements are adopted to capture the mixed-mode fracture. Based on the above triple-phase-field model, both 2D and 3D problems are modeled with good results. The heterogeneity of material is also considered. The simulations reveal that the compression strength and fracture mode of bedded shale are highly related to the orientations of the bedding plane and pre-existing fissure.

Effect of natural fractures on mechanical properties and fracture patterns of shale at microscopic scale: an example from the Lower Cambrian Niutitang formation in Qianbei region

In order to explore the influence of natural fractures on the mechanical properties and failure modes of shale at the micro scale, uniaxial compression numerical experiments were conducted on the shale of the Niutang Formation in northern Guizhou with different natural fracture angles using a rock failure process system and digital image processing technology. It is shown that the compressive strength of shale increases with the increase of natural crack inclination, and the growth rate of shale compressive strength also increases. Shale's microscopic fractures can generally be classified into four categories. The first category is to sprout along the natural cracks to the outside of the shale, and eventually form a crack similar to the "X" type (0°); the second category is to sprout along the natural cracks to the middle and outside of the shale, and eventually form an inverted "Y" type crack (15°, 30°); the third category is to sprout along the natural cracks to the middle and outside of the shale, and eventually form an inverted "Y" type crack (15°, 30°); the second type sprouts along the natural fractures toward the middle and outside of the shale, forming inverted "Y"-type fractures (15°, 30°); the third type cracks along the sides of the natural fractures, forming "Y"-type fractures (45°); and the fourth type does not crack along the natural fractures, forming "S"-type fractures (60°, 75°, and 90°). In the low natural fracture dip shale model, tensile damage mainly occurs, accompanied by a small amount of compressive shear damage; in the high natural fracture dip shale model, tensile damage and compressive shear damage account for a larger proportion in the fracture process.This suggests that the presence of natural cracks in shale has a significant impact on stress distribution. There are two main types of acoustic emission signal distribution and evolutionary features, the evolutionary features of acoustic emission signal distribution are of two types, 0°-45° test and 60°-90° test, and the difference is mainly reflected in the damage stage, the damage of shale with high natural fracture inclination is more intense, which is manifested by the decrease in the number of acoustic emission events, but the level of acoustic emission events in the damage stage is higher, which can reach 61788, 46605 and 94315, the shale with high natural fracture inclination is more brittle.

Folded calcite cracks in noncalcareous shales: a window into shale diagenesis and hydrothermal influence

ABSTRACT Shale diagenesis is not well understood, and cracks in shale contain important information about diagenetic conditions. The way these cracks open reveals physical changes in the sediment, and the infilling minerals provide insight into the chemical conditions of the formation water. Typically, the authigenic minerals filling the folded cracks are consistent with the chemical composition of the host rocks. For example, folded calcite cracks are found in limestone. This paper, however, focuses on a set of folded calcite cracks in noncalcareous black shales. The goal is to improve our understanding of shale diagenesis by deciphering the origins of these cracks. The cracks are sinuously to ptygmatically folded in a vertical view and weakly sinuous on the bedding plane. They are filled with calcite, bitumen, pyrite, or a combination of them. Evidence of bioturbation and low redox-sensitive trace-element ratios suggest suboxic to oxic depositional conditions of the shale. The cracks were likely opened by gas expansion in unconsolidated mud. The main mineral filling the cracks, calcite, was sourced from hydrothermal fluid that passed through the underlying dolomite. Hydrothermal influences are indicated by the presence of bornite and microcrystalline pyrite in the cracks, as well as Fe and Mn enrichment in the host sediments. Hydrothermal activity can also explain the presence of buddingtonite, an ammonium feldspar in the shale. The results of this study suggest that folded cracks filled by minerals, gradually narrowing towards the top, and lacking internal detrital matrix are likely formed during early diagenesis. The inconsistency between the chemical compositions of the infilling material and the host sediment requires further exploration to identify the source. Hydrothermal fluid passing through the underlying dolomite may be the source of folded calcite cracks in noncalcareous sedimentary rocks. These cracks resemble molar-tooth structures (MTS), which are sinuous cracks filled with microcrystalline calcite mostly found in Precambrian limestone and calcareous shales. If these cracks are indeed MTS, they may be an exception to the age and host-rock lithology constraints of MTS.

Investigation of crack propagation behavior on shales with different inclination based on ultra-fast time resolution method

The layer structures of shale greatly influence its crack propagation behavior. Nevertheless, the correlation between crack extension rates and mechanical parameters has not been well studied, especially, the relationship between the energy release rate and crack propagation rates. Consequently, there are unresolved issues regarding the effects of layer structure on the propagation of cracks in shale. In this paper, a series of three-point compressive loading tests were conducted on seven groups of shale semi-circular bend (SCB) samples with an inclination angle of 0°-90°. The entire fracture process was captured using the ultrafast time-resolution method with a resolution capability of up to 15 picoseconds. In addition, fracture surface information was obtained by a high-precision laser three-dimensional scanning system, and this information was utilized to categorize crack propagation behaviors, such as propagation along weak planes, intermittent penetration, and deflection penetration. Furthermore, a quantitative relationship was established between the energy-release rate and crack propagation rate, based on the first law of thermodynamics and the maximum energy release rate (MERR) criteria proposed by Griffith. The experimental results showed that there is a linear relationship between the energy-release rate and the propagation rate, which meets well with the established relationship. The experimental results indicated that symmetric loading does not result in significant angle localization during crack initiation. This suggests that crack propagation behavior in shale is a reflection of the interplay between energy-release rates and fracture resistance. Finally, this study evaluated the influence of the bedding angle on dissipated energy, and absorbed energy.

THE PATTERNS OF THIOPHENE DERIVATIVES FORMATION IN HIGH-SULPHUR OIL SHALE CRACKING

The composition of cracking products of high-sulphur shale oil from the Kashpir deposit is investigated under different process conditions (duration and temperature). The characteristic features of the influence of heat treatment conditions on changes in the composition of liquid products of oil shale cracking are established. It is shown that the cracking of oil shale organic matter is accompanied by the formation of a wide range of low-molecular sulphur-containing compounds that enter the composition of oils. The changes in the group composition of sulphur-containing compounds of oils have been studied, the features of the distribution of thiophene derivatives, benzo- and dibenzothiophene derivatives in the composition of liquid cracking products are revealed. It is shown that the depth and rate of destruction of sulphur-containing structural fragments of kerogen is significantly affected by the temperature and duration of the process. The data obtained will improve understanding of the patterns of thermal transformations of sulphur-containing structural fragments of organic matter in high-sulphur oil shale during cracking.

Influence of Heat Treatment Conditions on the Composition of Cracking Products of Oil Shale from the Kashpir Deposit

The cracking of oil shale from the Kashpir deposit was studied at various temperatures (425, 450, and 475°C) and process durations (40, 60, 80, and 100 min.). It was shown that the highest yields of liquid products and oils in their composition were achieved at a cracking temperature of 450°C and a duration of 100 min. An increase in the temperature and duration of cracking led to an increase in the concentration of С1–С5 hydrocarbons in the gaseous products by a factor of 2–5. Oils isolated from the liquid products of oil shale cracking consisted of 30–45% polycyclic aromatic hydrocarbons. It was established that an increase in the temperature and duration of cracking led to an increase in the concentration of IBP–360°C fractions in the composition of liquid products.

The Patterns of Thiophene Derivatives Formation in High-Sulphur Oil Shale Cracking

The Patterns of Thiophene Derivatives Formation in High-Sulphur Oil Shale Cracking

Failure and deformation characteristics of shale subject to true triaxial stress loading and unloading under water retention and seepage.

A multi-functional true triaxial fluid-structure coupling system was used to conduct water retention and seepage tests of shale under true triaxial loading and unloading stress paths. The stress–strain evolution of shale specimens under different experimental conditions was obtained, and the corresponding deformation and strength were analysed. The evolution and failure characteristics of cracks in shale were obtained by CT scanning images before and after the experiment. The results show that the volumetric strain of shale specimen increases first, then decreases and finally continues to increase with an increase in deviatoric stress under water retention, indicating that the volumetric change has experienced a compaction-expansion-compacting. The σ-ε1 curve of the sample increases first and then decreases, while the deformation in the σ2 direction shows the repeated compression and expansion. In the seepage test, the permeability–strain curve can be divided into two parts before and after fracture according to the σ-ε1 curve. Before fracture, the compression velocity of the specimen in the loading direction exceeds the expansion velocity in the unloading direction, resulting in a decrease in volume and a decrease in permeability. With an increase in deviatoric stress, fractures occur inside the particles and continue to spread from the tip until the fractures break through the shale specimen. The pore fissure area increases and the permeability of the sample increases rapidly. In terms of fracture evolution, for the water retention test, dense tensile and shear cracks appear on the failure plane perpendicular to the σ1 and σ3 directions, and complex shear fracture network appears on the failure plane perpendicular to the σ2 direction. For the seepage test, heavy shear failure occurs throughout the original fracture of the sample. With an increase in the penetration depth, the fracture shape on the failure surface perpendicular to the σ2 direction gradually changes from single to complex.

Research on Evolution Characteristics of Shale Crack Based on Simultaneous Monitoring of Multi-Parameters

Meso-crack evolution mechanism of shale is a key factor affecting the mechanical properties of shale. In order to explore evolution laws of cracks in shale during loading, a meso-crack monitoring system, loading test equipment and an automatic ultrasonic data acquisition system were set up. On this basis, a set of experimental apparatus simultaneous monitoring multi-parameters of shale micro-crack was designed, and destruction experiments of shale samples with different bedding angles were carried out to find out evolution characteristics of cracks. The results show the following: (1) The designed apparatus can monitor ultrasonic, mechanical and video information simultaneously of crack evolution in the entire process of shale destruction under load to provide information for analyzing acoustic and mechanical characteristic responses of crack propagation at key time nodes. (2) With an increase in load, shale will undergo four stages of destruction: crack initiation, propagation, penetration and overall failure. In the course of these stages, acoustic characteristics and mechanical characteristics are in good agreement, which proves the validity of predicting rock mechanical parameters with acoustic data. (3) During the loading process of shale, the main amplitude of acoustic wave is more sensitive than mechanical parameters to the change of rock cracks. Research results have important theoretical reference value for evaluating wall stability of shale gas horizontal well with ultrasonic data.

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Mud shale can serve as source or cap rock but also as a reservoir rock, and so the development of pores or cracks in shale has become of great interest in recent years. However, prior work using non-identical samples, varying fields of view and non-continuous heating processes has produced varying data. The unique hydrocarbon generation and expulsion characteristics of shale as a source rock and the relationship with the evolution of pores or cracks in the reservoir are thus not well understood. The present work attempted to monitor detailed structural changes during the continuous heating of shale and to establish possible relationships with hydrocarbon generation and expulsion by heating immature shale samples while performing in situ scanning electron microscopy (SEM) imaging and monitoring the chamber vacuum. Samples were heated at 20°C/min from ambient to 700°C with 30 min holds at 100°C intervals during which SEM images were acquired. The SEM chamber vacuum was found to change during sample heating as a consequence of hydrocarbon generation and expulsion. Two episodic hydrocarbon expulsion stages were observed, at 300 and 500°C. As the temperature was increased from ambient to 700°C, samples exhibited consecutive shrinkage, expansion and shrinkage, and the amount of structural change in the vertical bedding direction was greater than that in the bedding direction. At the same time, the opening, closing and subsequent reopening of microcracks was observed. Hydrocarbon generation and expulsion led to the expansion of existing fractures and the opening of new cracks to produce an effective fracture network allowing fluid migration. The combination of high-resolution SEM and a high-temperature heating stage allowed correlation between the evolution of pores or cracks and hydrocarbon generation and expulsion to be examined.

Investigation on the thermal cracking of shale under different cooling modes

Thermal stimulation method can be effectively utilized to enhance the flow performance in tight porous media with an induced thermal shock (TS) using the injection of cryogenic fluids. In order to reveal the thermal cracking behavior and the mechanism of shale under different cooling modes, thermal cooling laboratory experiments of shale samples were carried out in the current paper. Combined the numerical simulations and laboratory experiments, the thermal cracking behavior of shale under different cooling modes was studied. The laboratory experiments results show that the macroscopic thermal cracking tended to occur under thermal shock at a temperature of more than 400 °C. A heat transfer numerical simulation method under different cooling modes was established to analyze the temperature field distribution and the variation in the temperature gradient of shale from the perspective of heat transfer. For different cooling modes, the evolutionary trend of temperature gradient, thermal shock factor and dynamic thermal stress formed within the shale sample was consistent. The maximum values always occurred near the surface of the sample. Thermal shock factor, which can describe the ability of heat to cause damage to rocks, was introduced. The thermal shock factor could realize the quantitative classification of thermal cooling capacity. According to the evolutionary pattern of thermal shock factor, the specific time of the most serious internal fracture of shale samples could be determined. Dynamic thermal stress generated inside the shale under different cooling modes was also calculated to analyze the cause of shale cracking. The difference in the convective heat transfer coefficient of various cooling media was closely related to the fracture propagation. Thermal stimulation will be an efficient and a promising means to generate more complex fracture networks for the development of unconventional tight shale reservoirs using the combination of formation heat treatment (FHT) and thermal shock (TS).

Prediction and control model of shale induced fracture leakage pressure

Fractures gradually open under the action of fluid pressure in drilling shale gas reservoirs because of the existence of shale natural fractures, which leads to the leakage of expansible fractures. Induced fracture leakage is difficult to find and control in the early stage of drilling, resulting in great economic losses. The current model of induced fracture leakage pressure model is based on takes rock fracture criterion, which can only be used to judge whether the fracture is fractures created or not but cannot analyze the influence of fracture width change on leakage pressure after natural fracture of shale cracking. In addition, the model cannot control the occurrence of leakage. In this paper, the calculation method of fracture's width change under induced pressure is established. According to the field leakage rate data, a dynamic model of leakage pressure is established based on the parameters of time, leakage rate, fracture's width, fluid viscosity, and wellbore radius. The model is applied to calculate the dynamic change of leakage pressure on the Sichuan Shale Gas Field site and control the induced fracture's change to control leakage. Results show the following observations. (i) The fracture's width and leakage velocity of induced fracture increase with the increase of leakage pressure. Blocking the leakage when any leakage is found on the site is not advisable because it can increase the fracture's width artificially and increase leakage. (ii) The critical value of the fracture's width may cause severe leakage. When the leakage's differential pressure remains unchanged, the relationship between the fracture's width and leakage velocity refers to the power exponent change. The method of controlling the leakage pressure and reducing the fracture's width that is less than the critical leakage fracture degree is adopted for the leakage of the shale gas drilling in the Longmaxi Formation field Jiaoshiba, which effectively reduces the leakage amount. Taking a particular project, for example, controlling leakage pressure of induced fracture is given to verify the feasibility of the method.

Lab-Supported Hypothesis and Mathematical Modeling of Crack Development in the Fluid-Soaking Process of Multi-Fractured Horizontal Wells in Shale Gas Reservoirs

The objective of this study is to develop a technique to identify the optimum water-soaking time for maximizing productivity of shale gas and oil wells. Based on the lab observation of cracks formed in shale core samples under simulated water-soaking conditions, shale cracking was found to dominate the water-soaking process in multi-fractured gas/oil wells. An analytical model was derived from the principle of capillary-viscous force balance to describe the dynamic process of crack propagation in shale gas formations during water-soaking. Result of model analysis shows that the formation of cracks contributes to improving well inflow performance, while the cracks also draw fracturing fluid from the hydraulic fractures and reduce fracture width, and consequently lower well inflow performance. The tradeoff between the crack development and fracture closure allows for an optimum water-soaking time, which will maximize well productivity. Reducing viscosity of fracturing fluid will speed up the optimum water-soaking time, while lowering the water-shale interfacial tension will delay the optimum water-soaking time. It is recommended that real-time shut-in pressure data are measured and shale core samples are tested to predict the density of cracks under fluid-soaking conditions before using the crack propagation model. This work provides a shut-in pressure data-driven method for water-soaking time optimization in shale gas wells for maximizing well productivity and gas recovery factor.

Comparative study of porosity test methods for shale

Porosity is important in the assessment of gas shale reservoirs and has been widely tested as a basic characteristic of shale. Different test methods were employed to test the porosity, yet inconsistencies were found among the samples, testing methods, and researches in the Longmaxi Formation of the Sichuan Basin. In this paper, in order to determine the source of the inconsistencies, seven test methods are undertaken and the test results are compared intensely. The results show that the inconsistencies are due to sampling variations, test method limits, and sample sizes. It is suggested to test porosity with a relative big sample and by the method capable of covering a broad test range, to reduce the influence of sampling, testing method limit, and sample size. Furthermore, it needs to notice the test protocol, which can introduce unachieved status. Especially the water saturation has significant effect on shale porosity. In addition, the drying-wetting cycles could induce cracks in shale as well; hence, it is important to store the samples carefully, avoiding artificial porosity.

A Test Device System for Cracking Mud Shale under Hydraulic Fracturing

The exploitation of shale gas has always been a major problem, and the solution to this problem must start with the study of its nature. A kind of simulation device and monitoring method of mud shale cracking was designed and assembled by ourselves. First of all, made with two layers of the general principle and four layers of 60 ° prefabricated crack two groups of similar material sample of the shale, then in turn for each block of multistage hydraulic fracturing test, and the use of strain gauge for strain monitoring. Results show that under the condition of no native prefabricated crack, hydraulic direction tend to toward weak bedding plane direction of crack extension until she reached the weak bedding surface, and then the main cracks along the weak bedding surface directly, at the same time there are prefabricated crack in native and weak stratification plane, in stage and the area between the prefabricated crack priority area map cracking formation, the results for the exploitation of shale gas has important guiding significance.

Dynamic Crack Initiation Toughness of Shale under Impact Loading

The impact loading of a notched semi-circular bend (NSCB) specimen of outcrop shale in Changning Sichuan was carried out using a split Hopkinson pressure bar (SHPB) to study the effect of shale bedding on the dynamic crack initiation toughness. Three loading configurations were tested: Crack-divider, Crack-splitter and Crack-arrester loading. Bedding plane has a significant effect on the crack initiation of shale. Under the Crack-divider and Crack-splitter modes, shale had lower dynamic crack initiation toughness. The dynamic crack initiation toughness of the shale was affected by the loading rate for all three loading configurations. The correlation between loading rate and dynamic crack initiation toughness was most significant for the Crack-arrester mode, while the Crack-splitter mode was the weakest. When loading was carried out on Crack-arrester, the bedding plane could change the direction of crack growth. In the Crack-splitter mode, only a small impact energy was needed to achieve effective expansion of a crack. The research results provide a theoretical basis for shale cracking.