Crack propagation and hydraulic fracturing in different lithologies

Hou, Zhenkun; Cheng, Hanlie; Sun, Shuwei; Chen, Jun; Qi, Dian-Qing; Liu, Zhibo

doi:10.1007/s11770-019-0764-3

Cited by 109 publications

(85 citation statements)

References 18 publications

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“…Therefore, when the volume of fracturing fluid injected is fixed, the fracture half-length will increase. ,, In addition, with the increase of the elastic modulus, it is easier to form a high-stress concentration area at the fracture tip. Then more energy is released during the formation of new fractures, thus promoting the fracture propagation. , Meanwhile, the increase of the elastic modulus also results in less energy loss in the reservoir compression . For the NGH reservoir with high hydrate saturation, it has a larger strength and elastic modulus.…”

Section: Resultsmentioning

confidence: 99%

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2D Numerical Simulation of Hydraulic Fracturing in Hydrate-Bearing Sediments Based on the Cohesive Element

Cheng

Sun

et al. 2021

Energy Fuels

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There are major problems in offshore hydrate production tests, such as low gas production, limited hydrate decomposition area, and short stable production duration. Hydraulic fracturing is regarded as an effective way to improve gas production from a natural gas hydrate (NGH) reservoir. However, the fracture initiation, propagation, and morphology of hydraulic fracturing in the NGH reservoir are rarely investigated. In this work, a 2D numerical model based on the cohesive element is built to study the effects of reservoir properties and fracturing execution parameters on hydraulic fracturing of the NGH reservoir. With the increase of gas hydrate saturation, the fracture initiation pressure increases obviously, and the fracture becomes longer and narrower, which can be attributed to the increase of the strength and elastic modulus of hydrate-bearing sediments. Fracture initiation pressure decreases with the increase of reservoir intrinsic permeability due to the filtration of fracturing fluid. The stress in the normal direction of the fracture surface has a more significant influence on the initiation, propagation, and size of the fracture. With the increase of in situ horizontal stress, the strength of hydratebearing sediments increases, leading to an obvious increase of fracture initiation pressure and the formation of wider and shorter fractures. In addition, a higher injection rate of fracturing fluid is conducive to the formation of wider and longer fractures. At high injection rates, the effects of fracturing fluid viscosity on fracture initiation pressure and fracture morphology are more obvious. The results obtained in this work will bring a better understanding of hydraulic fracturing in NGH reservoirs and help to construct potential reservoir stimulation strategies.

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Section: Resultsmentioning

confidence: 99%

“…31,58 Meanwhile, the increase of the elastic modulus also results in less energy loss in the reservoir compression. 59 For the NGH reservoir with high hydrate saturation, it has a larger strength and elastic modulus. On the one hand, the fracturing pressure is higher, thus requiring higher performance of the fracturing pump.…”

Section: Resultsmentioning

confidence: 99%

2D Numerical Simulation of Hydraulic Fracturing in Hydrate-Bearing Sediments Based on the Cohesive Element

Cheng

Sun

et al. 2021

Energy Fuels

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“…Scientists have recognized the advantages of variable pitch generators. Figure 1 shows the variable-speed constant-frequency doubly fed wind power generation system [17].…”

Section: Vscf Doubly Fed Wind Power Generation Systemmentioning

confidence: 99%

Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

Zhang

et al. 2022

Wireless Communications and Mobile Computing

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The depletion of nonrenewable energy and climate lead to increasingly bad environment. The efficient development of new energy has become an urgent problem to be solved. As a kind of new energy, how to effectively develop and utilize wind energy has aroused widespread concern all over the world. In this paper, a three-phase static a-b-c coordinate system is used for transformation. Taking the variable-speed constant-frequency doubly fed wind power generation system as the control object, the technology of generator power decoupling control is realized. The rotor side and grid side power converters adopt vector control methods based on stator flux orientation and grid voltage orientation, respectively. In this paper, the motion equation, flux equation, voltage equation, and electromagnetic torque equation of the motor are established. Vector-oriented control technology is used to control the generator. The control model of the VSCF doubly fed wind power generation system is established by using the simulation software PSCAD, and the simulation experiment is carried out. The feasibility of the power decoupling control method based on vector control is verified. The change trend of the active power of the power generation system is consistent with that of the wind speed, which shows that the control system has good stability. Using the field-oriented vector control method, the dual PWM controller can independently control the active power and reactive power. This greatly simplifies the nondecoupling control function equation in the expression. The dual PWM controller is well adjusted to minimize the power loss of the wind power generation system.

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“…However, according to statistical data, 1.5% of schools in China carried out innovation and entrepreneurship education from 2013 to the end of 2020, while the total amount of innovation and entrepreneurship education funds accounted for only 0.1% of the total national income in recent years. According to the statistical bulletin on the development of education industry in 2018, at the end of 2018, schools carrying out innovation and entrepreneurship education in the southeast coastal areas accounted for 30%, while schools carrying out innovation and entrepreneurship education in the western region accounted for only 1% [4][5][6]. The national innovation and Entrepreneurship Education Fund were only 10 million, accounting for 0.0025% of the national total annual income, an increase of 5.2% compared with last year.…”

Section: Introductionmentioning

confidence: 99%

Construction of Educational Model for Computer Majors in Colleges and Universities

Jiang

2022

Wireless Communications and Mobile Computing

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With the rapid development of the Internet era and the high popularity of computers, China’s economy, politics, and culture have made rapid progress in recent years. In order to adapt to this era of rapid change, China’s higher education has also undergone great changes and carried out reform and innovation. As the top priority in the Internet era, computers should be reformed first. The traditional education model is mainly teacher-centered and classroom-centered. The disadvantages of this teaching mode are that students’ subjective initiative cannot be fully developed and brought into play. Traditional teaching pays attention to knowledge teaching and ignores ability training. It emphasizes speaking and neglects practice. Therefore, in order to meet the development needs of the new era and cultivate modern talents, colleges and universities began to explore the innovation and entrepreneurship education mode. There is an application of TRIZ theory to the cultivation of innovation and entrepreneurship education, and TRIZ theory is a theory for solving invention problems. Its main content is to find its own laws in the process of technological evolution and analyze the laws to get a general solution, but there are many obstacles in exploring the mode of innovation and entrepreneurship education; for example, many governments do not support this education reform and do not broadcast relevant education and teaching funds for schools, resulting in uneven configuration of software and hardware in schools. According to the survey, the proportion of innovation and entrepreneurship education in the eastern coastal areas is as high as 70%, while the proportion of innovation and entrepreneurship education in the central and western regions is only 10%. This set of data shows that regional differences are the main reason for the differences in education development. In terms of the proportion of education funds, although the annual education funds will gradually increase in recent years, the proportion is still a drop in the bucket in front of huge fiscal revenue, with the highest being only 0.1%. Therefore, in order to improve the current situation of innovation and entrepreneurship education mode in colleges and universities, according to their own characteristics, the reform is carried out from the aspects of practical ability, competition participation, and training plan, and the BP neural network model is introduced to predict and analyze the effect of teaching methods. The results of this paper are investigated and analyzed. Finally, the investigation on the development of KAB course and SYB course and the analysis on the stability and error of BP neural network are within the allowable range, this shows that the model established in this paper is more favored by students than the traditional teaching methods, more in line with the social reality, the effect is more ideal, and the result is more stable.

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Crack propagation and hydraulic fracturing in different lithologies

Cited by 109 publications

References 18 publications

2D Numerical Simulation of Hydraulic Fracturing in Hydrate-Bearing Sediments Based on the Cohesive Element

2D Numerical Simulation of Hydraulic Fracturing in Hydrate-Bearing Sediments Based on the Cohesive Element

Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

Construction of Educational Model for Computer Majors in Colleges and Universities

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