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Project Details
Funding Scheme : Early Career Scheme
Project Number : 27205918
Project Title(English) : Waterless fracturing for unconventional energy production: Coupled geomechanics–flow modeling and investigations 
Project Title(Chinese) : 無⽔壓裂法於⾮傳統型能源⽣產的應⽤: 岩⼟⼒學與流體耦合建模及研究 
Principal Investigator(English) : Dr Choo, Jinhyun 
Principal Investigator(Chinese) :  
Department : Department of Civil Engineering
Institution : The University of Hong Kong
E-mail Address : jchoo@hku.hk 
Tel :  
Co - Investigator(s) :
Panel : Engineering
Subject Area : Civil Engineering, Surveying, Building & Construction
Exercise Year : 2018 / 19
Fund Approved : 500,000
Project Status : Completed
Completion Date : 31-12-2021
Project Objectives :
To develop a mathematical model capable of reproducing the physical processes in waterless fracturing methods
To develop an accurate and efficient numerical method for coupled geomechanics and multiphase flow in fracturing porous media
To investigate the control of the properties of injecting fluid on the fluid-driven fracturing process for energy recovery
Abstract as per original application
(English/Chinese):
Realisation of objectives: The three objectives of the project have been well achieved. First, we have developed novel modeling frameworks for waterless fracturing methods. These developments include a series of phase-field models for mixed-mode fracture in quasi-brittle rocks and an anisotropic and viscoplastic constitutive model for shale based on layered microstructure homogenization. Second, we have developed accurate and efficient numerical techniques for coupled geomechanics and flow in porous media. Specifically, we have spearheaded enriched Galerkin methods and material point methods for coupled poromechanics, in which the inf-sup stability problem in undrained deformation is efficiently stabilized for each kind of method. Lastly, through the application of these advanced mathematical models and numerical techniques, we have investigated how the properties of the injecting fluid controls the physical process of fluid-driven fracture for energy recovery.
Summary of objectives addressed:
Objectives Addressed Percentage achieved
1.To develop a mathematical model capable of reproducing the physical processes in waterless fracturing methodsYes100%
2.To develop an accurate and efficient numerical method for coupled geomechanics and multiphase flow in fracturing porous mediaYes100%
3.To investigate the control of the properties of injecting fluid on the fluid-driven fracturing process for energy recoveryYes100%
Research Outcome
Major findings and research outcome: A primary outcome of this project is a class of phase-field formulations for modeling discontinuities and fractures in geologic materials. Over the past several years, phase-field modeling has become a state-of-the-art method for computational simulation of fractures in various kinds of solids. However, the existing phase-field formulations do not incorporate several critical features of discontinuities and fractures in geologic materials: frictional contact, pressure-dependence, quasi-brittleness, and their combined impact on mixed-mode cracking. In this project, we have developed a class of novel phase-field formulations that incorporate these features in a well verified and validated manner. Remarkably, these phase-field approaches allow one to simulate the combination of cohesive tensile fracture and frictional shear fracture without any algorithms for surface tracking and contact constraints. Another key outcome related to geomechanical modeling is a two-scale constitutive model for anisotropic and viscoplsatic shale. The constitutive model utilizes semi-analytical homogenization of a bilayer microstructure comprised of soft and hard layers, such that anisotropic behavior naturally emerges in the macroscopic level even when the individual layers are isotropic. As a result, the anisotropic viscoplastic constitutive model can be calibrated with a lower number of parameters compared with existing constitutive models for the same purpose, and all the parameters have clear physical meanings. In addition, we have developed accurate and efficient numerical methods for simulating coupled geomechanics and flow in porous media. They include enriched Galerkin methods for locally conservative solutions to poromechanical problems, and material point methods for simulating fluid-saturated porous media undergoing large deformations. For both types of methods, we have developed stabilization techniques that efficiently address the inf-sup stability problem in undrained deformation. Last but not least, by applying these advanced simulation methodologies, we have investigated how the properties of the injecting fluid controls the physics involved in waterless fracturing methods for energy recovery. Our findings include that when the fracturing fluid is far less viscous than water, the breakdown pressure becomes much lower, and the rock matrix experiences much more distributed microcracking. These changes may have significant effects on the performance and environmental impacts of unconventional resources recovery.
Potential for further development of the research
and the proposed course of action:		 The research may be further developed in the following way. Firstly, one can improve the numerical modeling methodology such that it incorporates more physical aspects in the waterless fracturing process. For example, it is highly desirable to enhance the methodology for mixed-mode fracture in anisotropic and viscoplastic shale, by combining the phase-field models and the constitutive model developed in this research. Another line of important future work improving the methodology is to include chemical and thermal effects such as adsorption into the shale matrix. Once the modeling methodology becomes improved as described above, one may use it to further elucidate the physics involved in waterless fracturing methods in more realistic settings. The improved simulation methodology and physical understanding will allow us to better deploy waterless fracturing methods in the large-scale commercial production of unconventional resources.
Layman's Summary of
Completion Report:		 The use of unconventional resources (e.g. shale gas) is essential to meeting the ever-growing demands for energy resources until renewable energy technologies become mature enough to replace fossil fuels completely. However, the current methods for extracting unconventional resources can give rise to other environmental problems, particularly consumption and contamination of freshwater resources and induced earthquakes. These problems are mainly resulted from the use of hydraulic fracturing, in which a large volume of chemically treated water is injected into deep underground to fracture low-permeable rock formations. A promising option to counteract these problems is to use waterless fracturing methods, whereby the water in hydraulic fracturing is replaced by non-aqueous fluids such as liquid/supercritical carbon dioxide. However, to apply such waterless fracturing methods in the large-scale commercial production of unconventional resources, we should be able to understand, predict and control the complex physics involved in waterless fracturing processes. This project has developed a family of novel computational methods for high-fidelity simulation of waterless fracturing processes in shale rocks. The methods have been applied to decipher hitherto unknown aspects of the physics involved in waterless fracturing processes. The outcomes will help advance waterless fracturing technologies for more environmentally friendly recovery of unconventional resources.
Research Output
Peer-reviewed journal publication(s)
arising directly from this research project :
(* denotes the corresponding author)
Year of
Publication		 Author(s) Title and Journal/Book Accessible from Institution Repository
2019 Jinhyun Choo*  Stabilized mixed continuous/enriched Galerkin formulations for locally mass conservative poromechanics. Computer Methods in Applied Mechanics and Engineering, 357, 112568.  No 
2019 Qi Zhang, Jinhyun Choo, Ronaldo I. Borja*  On the preferential flow patterns induced by transverse isotropy and non-Darcy flow in double porosity media. Computer Methods in Applied Mechanics and Engineering, 353, 570–592.  No 
2020 Fan Fei, Jinhyun Choo*  A phase-field method for modeling cracks with frictional contact. International Journal for Numerical Methods in Engineering, 121(4), 740–762.  No 
2020 Yidong Zhao, Jinhyun Choo*  Stabilized material point methods for coupled large deformation and fluid flow in porous materials. Computer Methods in Applied Mechanics and Engineering, 362, 112742.  No 
2020 Fan Fei, Jinhyun Choo*  A phase-field model of frictional shear fracture in geologic materials. Computer Methods in Applied Mechanics and Engineering, 369, 113265.  No 
2021 Jinhyun Choo*, Shabnam J. Semnani, Joshua A. White  An anisotropic viscoplasticity model for shale based on layered microstructure homogenization. International Journal for Numerical and Analytical Methods in Geomechanics, 45(4), 502–520.  No 
2021 Fan Fei, Jinhyun Choo*  Double-phase-field formulation for mixed-mode fracture in rocks. Computer Methods in Applied Mechanics and Engineering, 376, 113655.  No 
2021 Teeratorn Kadeethum, Sanghyun Lee, Francesco Ballarin, Jinhyun Choo, and Hamid M. Nick*  A locally conservative mixed finite element framework for coupled hydro-mechanical-chemical processes in heterogeneous porous media. Computers & Geosciences, 152, 104774.  No 
2021 Jinhyun Choo*, Ammar Sohail, Fan Fei, Teng-fong Wong  Shear fracture energies of stiff clays and shales. Acta Geotechnica, 16(7), 2291–2299.  No 
2021 Sabrina C.Y. Ip, Jinhyun Choo, Ronaldo I. Borja*  Impacts of saturation-dependent anisotropy on the shrinkage behavior of clay rocks. Acta Geotechnica, 16(11), 3381–3400.  No 
Fan Fei, Jinhyun Choo*, Chong Liu, Joshua A. White  Phase-field modeling of rock fractures with roughness. International Journal for Numerical and Analytical Methods in Geomechanics, doi: 10.1002/nag.3317  No 
Jinhyun Choo*, Yidong Zhao, Yupeng Jiang, Minchen Li, Chenfanfu Jiang, Kenichi Soga  A barrier method for frictional contact on embedded interfaces. Under review.  No 
Fan Fei, Jinhyun Choo*  Extended Barton–Bandis model for rock joints under cyclic loading: Formulation and implicit algorithm. Under review.  No 
Recognized international conference(s)
in which paper(s) related to this research
project was/were delivered :
Month/Year/City Title Conference Name
Houston Anisotropic creep in shale gas reservoir rocks: Impacts of constitutive behavior on field-scale deformations  55th US Rock Mechanics/Geomechanics Symposium 
Other impact
(e.g. award of patents or prizes,
collaboration with other research institutions,
technology transfer, etc.):
Realisation of the education plan:
  SCREEN ID: SCRRM00542