Experimental study on crack propagation control and mechanism analysis of directional hydraulic fracturing

Cheng, Yugang; Lu, Yiyu; Ge, Zhaolong; Cheng, Liang; Zheng, Jingwei; Zhang, Wenfeng

doi:10.1016/j.fuel.2018.01.034

Cited by 111 publications

(49 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies [9,31,32] have shown that main hydraulic fractures can be oriented in coal seams as shown in Figure 3. The computed tomography (CT) graph from [11] in Figure 3 is used here to demonstrate the phenomenon intuitively. Based on these, a model of gas extraction from coal seam after directional hydraulic fracturing was constructed in this study.…”

Section: A Conceptual Modelmentioning

confidence: 99%

“…Therefore, it is crucial for gas extraction from a coal seam stimulated by directional hydraulic fracturing to consider the different type of gas flow at different scales under thermo-hydro-mechanical (THM) coupling conditions ( Figure 2). In the previous study [11], when hydraulic slotting deviation angle or the horizontal stress difference is small, the hydraulic fracture can be oriented to expand along the direction of the slotting arrangement and connect fracturing borehole to slotting borehole. Coal is typical a dual-porosity reservoirs consisting of matrix and natural fractures, termed cleats [14,15].…”

Section: Introductionmentioning

confidence: 98%

“…As a result, gas drainage from a coal seam stimulated by fracturing can be inefficient. To enlarge the slotting influence scope and resolve the issue of disorderly crack propagation in conventional hydraulic fracturing, a directional hydraulic fracturing method integrated hydraulic slotting and hydraulic fracturing is proposed [9][10][11][12][13], as shown in Figure 1. This method utilizes a high-pressure water jet to slot in the fracturing borehole and directional boreholes along the coal bed inclination, and then hydraulic fracturing is performed in the fracturing borehole.…”

Section: Introductionmentioning

confidence: 99%

“…is the volume strain of coal and σ σ − = /3 kk is the mean stress. The sorption-induced strain ε s is generally represented by a Langmuir-type equation, which is defined as: The geometry of the model used for numerical simulation (CT) graph adapted from[11]). …”

mentioning

confidence: 99%

See 3 more Smart Citations

Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

Zhang

Sun

et al. 2019

Applied Sciences

View full text Add to dashboard Cite

Although numerous studies have tried to explain the mechanism of directional hydraulic fracturing in a coal seam, few of them have been conducted on gas migration stimulated by directional hydraulic fracturing during coal mine methane extraction. In this study, a fully coupled multi-scale model to stimulate gas extraction from a coal seam stimulated by directional hydraulic fracturing was developed and calculated by a finite element approach. The model considers gas flow and heat transfer within the hydraulic fractures, the coal matrix, and cleat system, and it accounts for coal deformation. The model was verified using gas amount data from the NO.8 coal seam at Fengchun mine, Chongqing, Southwest China. Model simulation results show that slots and hydraulic fracture can expand the area of gas pressure drop and decrease the time needed to complete the extraction. The evolution of hydraulic fracture apertures and permeability in coal seams is greatly influenced by the effective stress and coal matrix deformation. A series of sensitivity analyses were performed to investigate the impacts of key factors on gas extraction time of completion. The study shows that hydraulic fracture aperture and the cleat permeability of coal seams play crucial roles in gas extraction from a coal seam stimulated by directional hydraulic fracturing. In addition, the reasonable arrangement of directional boreholes could improve the gas extraction efficiency. A large coal seam dip angle and high temperature help to enhance coal mine methane extraction from the coal seam.

show abstract

Section: A Conceptual Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

Zhang

Sun

et al. 2019

Applied Sciences

View full text Add to dashboard Cite

show abstract

“…Although a great number of researches on directional fracturing technology have been studied by many experts and scholars, [25][26][27] hydraulic fracturing is easy to cause stress concentration in coal body, which leads to coal and gas outburst. 28 Hydraulic flushing can enlarge borehole diameter by flushing coal body with high-pressure water jet, which is equivalent to large diameter borehole, and the larger the borehole diameter is, the larger the pressure relief range of the borehole and the permeability of the coal around the borehole are. 29 Hydraulic slotting can enhance permeability by cutting coal seam fractures with high-pressure water jet.…”

Section: Introductionmentioning

confidence: 99%

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Qin

Wei

Lou

et al. 2020

Energy Science & Engineering

View full text Add to dashboard Cite

Predrainage of gas by cross‐boreholes is an important method to prevent coal and gas outbursts in the process of a coal roadway excavation. Limitations of technologies and poor effects of preventing coal and gas outbursts occur in the coal seam with a soft layer. In this study, a new hydraulic caving technology for cross‐boreholes has been proposed to solve this problem. A CT equipment was used to observe the development of coal fissures around cross‐boreholes in the coal seam with a soft layer. The plastic zone range and permeability distribution of ordinary hydraulic slotting technologies and the new hydraulic caving technology also were compared by numerical simulation. The field test of hydraulic caving was taken in the Xuehu Mine (China). The results show that the fracture development degree of soft coal is greater than that of hard coal at the same distance from cross‐boreholes. The fracture development degree in the plastic zone is greater than that in the elastic zone. The hydraulic caving technique can achieve the same effect as the ordinary hydraulic slotting with less workload. The mass of coal discharged from a cross‐borehole was 1.15 t/m and the average methane concentration of single drainage borehole increased by 1.09‐4.1 times, and the average methane extraction amount of single drainage borehole increased by 6.06 times. Elimination of coal and gas outburst had been completed after 110 days of extraction in the area of hydraulic caving, and Q and S values are lower than the critical value during roadway excavation. It is conclusion that hydraulic caving technique can effectively improve the permeability and rapidly eliminate coal and gas outburst in the coal seam with a soft layer.

show abstract

Influence of High Pressure Drop Rates on Fatigue Crack Growth

Michiels

Geimer

2022

Chem Eng & Technol

View full text Add to dashboard Cite

Hydraulic components in mobile machines are subjected to varying conditions and loads, which limit their lifetime. In particular, high pressure drop rates are suspected to increase fatigue crack growth rates. Existing studies on the fluidstructure interaction inside fatigue cracks during fast pressure drops do not explain increased crack growth in hydraulic systems. A laminar flow model was developed to simulate the fluid flow inside a crack under periodic pressure loads. The viscosity restrained the oil inside the crack, and the mechanical resistance of the closing crack led to a high pressure increase. Knowledge of the pressure profiles inside fatigue cracks helps to estimate the effective fatigue damage during transient loads.

show abstract

Experimental study on crack propagation control and mechanism analysis of directional hydraulic fracturing

Cited by 111 publications

References 38 publications

Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

Influence of High Pressure Drop Rates on Fatigue Crack Growth

Contact Info

Product

Resources

About