Experimental investigation on the failure and acoustic emission characteristics of shale, sandstone and coal under gas fracturing

Hou, Peng; Gao, Feng; Ju, Yang; Liang, Xin; Zhang, Zhizhen; Cheng, Hongmei; Gao, Yanan

doi:10.1016/j.jngse.2016.08.048

Cited by 53 publications

(31 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These tests are crucial to understand the effect of material composition and local heterogeneities on the mechanical response of rocks, which, because of their natural genesis, significantly differ from one to another (Bobko and Ulm 2008;Veytskin et al 2017). Hou et al (2016) compared the behavior of shale, coal and sandstone specimens subjected to high-pressure fluid-driven 1 3 fracturing, and observed how different microscopic composition of these materials leads to important differences in the measured values of mechanical properties, strains and crack patterns. Kim et al (2012) also performed a comparative study between shale, gneiss and schist rocks samples, investigating the influence of their composition and direction of bedding planes on their thermo-mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

et al. 2018

View full text Add to dashboard Cite

Reliable prediction of fracture process in shale-gas rocks remains one of the most significant challenges for establishing sustained economic oil and gas production. This paper presents a modeling framework for simulation of crack propagation in heterogeneous shale rocks. The framework is on the basis of a variational approach, consistent with Griffith's theory. The modeling framework is used to reproduce the fracture propagation process in shale rock samples under standard Brazilian disk test conditions. Data collected from the experiments are employed to determine the testing specimens' tensile strength and fracture toughness. To incorporate the effects of shale formation heterogeneity in the simulation of crack paths, fracture properties of the specimens are defined as spatially random fields. A computational strategy on the basis of stochastic finite element theory is developed that allows to incorporate the effects of heterogeneity of shale rocks on the fracture evolution. A parametric study has been carried out to better understand how anisotropy and heterogeneity of the mechanical properties affect both direction of cracks and rock strength.

show abstract

Section: Introductionmentioning

confidence: 99%

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The fracture networks of jointed reservoirs may be very complex due to the reopening of the existing joints, the expansion of hydraulic fractures, and the intersection between joints and hydraulic fractures [31]. Nitrogen fracturing experiments were conducted on shale samples vertical and parallel to the bedding plane; the results indicated that a relative complex fracture surface is formed in the shale sample vertical to the bedding plane [32]. He et al [33] performed hydraulic fracturing on shale with bedding planes; the results showed that the bedding planes in shale formation have a significant influence on the propagation of hydraulic fractures.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of Fracture Propagation in Jointed Shale Reservoirs under CO₂ Fracturing

Zhang

Liu

et al. 2019

Geofluids

View full text Add to dashboard Cite

Water-based hydraulic fracturing for the exploitation of shale gas reservoirs may be limited by two main factors: (1) water pollution and chemical pollution after the injection process and (2) permeability decrease due to clay mineral swelling upon contact with the injection water. Besides, shale rock nearly always contains fractures and fissures due to geological processes such as deposition and folding. Based on the above, a damage-based coupled model of rock deformation and gas flow is used to simulate the fracturing process in jointed shale wells with CO 2 fracturing. We validate our model by comparing the simulation results with theoretical solutions. The research results show that the continuous main fractures are formed along the direction of the maximum principal stress, whilst hydraulic fractures tend to propagate along the preexisting joints due to the lower strength of the joints. The main failure type is tensile damage destruction among these specimens. The preexisting joints can aggravate the damage of the numerical specimens; the seepage areas of the layered jointed sample, vertical jointed sample, and orthogonal jointed sample are increased by 32.5%, 29.16%, and 35.05%, respectively, at time t = 39 s compared with the intact sample. The preexisting horizontal joints or vertical joints promote the propagation of hydraulic fractures in the horizontal direction or vertical direction but restrain the expansion of hydraulic fractures in the vertical or horizontal direction.

show abstract

“…Based on experimental observations, Liu et al [15] concluded that an induced-fluid fracture propagated along with the least resistance or the shortest propagation path. Acoustic emission technology and gaseous tracer have also been applied in laboratory experiments to investigate fracturing behaviors [16,17]. The aforementioned experiments mainly explored the hydraulic fracturing mechanism from external loading conditions and hydraulic fracturing treatments.…”

Section: Introductionmentioning

confidence: 99%

Discrete Element Analysis for Hydraulic Fracture Propagations in Laminated Reservoirs with Complex Initial Joint Properties

Dou

Wang

et al. 2019

Geofluids

View full text Add to dashboard Cite

Previous studies on hydraulic fracturing mainly focus on the effects of the in-situ stress state, permeability, fracturing fluids, and approach angle in homogeneous rocks, but the impacts of joint mechanical properties in laminated shale reservoirs on the propagation and formation of the fracture network are still unclear. In this study, a coupled fluid-mechanical model was developed to investigate the impacts of joint mechanical properties on hydraulic fracture propagation. Then, this model was validated with Blanton’s criterion and some experimental observations on fracture morphology. Finally, a series of numerical simulations were conducted to comparatively analyze the impacts of joint mechanical properties on the total crack number, the percentage and distribution of each fracture type, the process of crack propagation, and the final fracture morphology. Numerical results show that the cracking behaviors induced by joint mechanical properties vary with the approach angle. Joint strength has a significant influence on the generation of matrix tensile cracks. The tensile-to-shear strength ratio plays an even more important role in the shear slips of bedding planes and is conducive to the formation of complex fracture morphology.

show abstract

Experimental investigation on the failure and acoustic emission characteristics of shale, sandstone and coal under gas fracturing

Cited by 53 publications

References 22 publications

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Numerical Simulations of Fracture Propagation in Jointed Shale Reservoirs under CO₂ Fracturing

Discrete Element Analysis for Hydraulic Fracture Propagations in Laminated Reservoirs with Complex Initial Joint Properties

Contact Info

Product

Resources

About

Experimental investigation on the failure and acoustic emission characteristics of shale, sandstone and coal under gas fracturing

Cited by 53 publications

References 22 publications

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

Numerical Simulations of Fracture Propagation in Jointed Shale Reservoirs under CO2 Fracturing

Discrete Element Analysis for Hydraulic Fracture Propagations in Laminated Reservoirs with Complex Initial Joint Properties

Contact Info

Product

Resources

About

Numerical Simulations of Fracture Propagation in Jointed Shale Reservoirs under CO₂ Fracturing