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Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation./
Author:	Yang, Jie.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
Description:	169 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-06, Section: B.
Contained By:	Dissertations Abstracts International83-06B.
Subject:	Propagation. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28827915
ISBN:	9798494450906

Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation.
Yang, Jie.

Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 169 p.

Source: Dissertations Abstracts International, Volume: 83-06, Section: B.

Thesis (Ph.D.)--Stanford University, 2021.

This item must not be sold to any third party vendors.

Rate-dependent behavior associated with deformation and fracturing of materials poses significant challenges for modeling. In addition to the complications of the viscoelastic response, the speed of fracture propagation reflects micromechanical mechanisms in the fracture process zone(FPZ). In order to represent these complicated behaviors, a thermodynamically consistent, rate-dependent fracture model is required. Based on rigorous thermodynamic principles, we derive a rate-dependent phase-field mechanical model coupled with single-phase fluid flow in both the matrix and the fracture. The model is guaranteed to satisfy energy conservation during fracture propagation. The proposed phase-field model is tested against several benchmark problems on solid-fluid coupling, fluid-driven fracture propagation and rate-dependent viscoelastic deformation. The model serves as a strong basis for investigating rate-dependent fracturing experiments and for making predictions of material behaviors under new conditions.With the developed numerical model, we are able to apply our simulator to a wide range of mechanical problems. Specifically, we are interested in addressing the rate-dependent deformation and fracturing in shales. Shale gas plays an important role in addressing rising global energy demand and national energy security. To date, hydraulic fracturing with slickwater treatment continues to be the most widely-used stimulation method for shale gas reservoirs. A number of alternatives have been explored including fracturing using nonaqueous fluids, such as supercritial carbon dioxide (sc-CO2), to reduce water consumption and circumvent production inefficiency caused by water blocking and clay swelling. Experimental studies have compared the behavior of CO2 to water injection.Due to differences in experimental setup and core sample preparation, inconsistent or even apparently contradictory conclusions have resulted. In this study, we propose a numerical model capable of reproducing the hydraulic fracturing experiments found in the literature and we investigate the impact of various material and fluid properties on the resulting fracture. Our finite element numerical model is adapted from a rate-dependent phasefield fracture model developed separately. Most importantly, we studied the effect of fluid properties and confining condition on the breakdown pressure, and how the topology of the resulting fracture plane changes. We showed that sc-CO2 injection can result in breakdown pressure about 1.75 times that of water under strict sealing and confining conditions in the laboratory for the shale studied. sc-CO2 also produces fast-propagating fractures with less influence of the bedding plane on fracture topology. Our model offers a straightforward explanation and reconciliation of existing experimental observations, as well as a means to extrapolate to unseen conditions.In addition to the macroscopic fractures created during hydraulic fracturing, microfractures can be induced during shale maturation. Recent studies suggested the importance of microfracture networks to recovery that connect localized zones with large organic content to the inorganic matrix. We applied our numerical model to a shale analog system and performed joint modeling and experimental study to examine the onset, formation, and evolution of microfracture networks as shale matures. Both the stress field and fractures are simulated and imaged. The experimental setup was fitted to utilize photoelasticity principles coupled with birefringence properties of gelatin to explore visually the stress field of the gelatin as the fracture network developed. Stress optics image analysis and linear elastic fracture mechanics (LEFM) principles for crack propagation were used to monitor fracture growth for each gelatin type. Observed and simulated responses suggest gas diffusion within and deformation of the gelatin matrix as predominant mechanisms for energy dissipation depending on gelatin strength. LEFM, an experimental estimation of principal stress development with fracture growth, at different stages was determined for each gelatin rheology. The interplay of gas diffusion and material deformation determines the resulting fracture density and pattern.For typical applications in subsurface engineering, the domain of interest is often orders of magnitude larger than the underlying fracture networks. Instead of developing a sophisticated phenomenological model, a constitutive modeling approach called multi-scale constitutive model has become increasing popular in the computational mechanics community. Multi-scale constitutive models provide a convenient way of describing complex material dynamics with varying length scales without explicitly constructing a phenomenological model. For certain materials, the parameter space is extremely large thanks to the multi-scale nature of the micro-structure. Take shale as an example, the heterogeneity of organic and inorganic compounded with convoluted layering and embedding structures could range from micron scale to centimeter scale. We developed a variational multi-scale constitutive model for rate-dependent fractured media. By assuming scale separation, we model the homogenized stress-strain response in a representative elementary volume (REV) and upscale the resulting stress tensor and material tangent to macroscopic domain. We introduced basic implementation workflow in an FEM simulator framework. We then validated our multi-scale constitutive model against several benchmark tests. Finally, we demonstrated the effectiveness of the multi-scale model in a real-world fracturing experiment on shale.In terms of fluid flow in fractured media, naturally occurring fracture networks often exhibit complex topology on various scales. And it is often intractable to model simultaneously their effects across different scales. Assuming scale separation, Dual-Porosity Dual-Permeability (DPDK) models can be used to simulate the fluid flow in the naturally fractured porous media. However, when applied to formations with highly nonlinear flow properties, existing models often fail to deliver accurate results within a reasonable computation budget. In this work, we present a novel semi-analytical solution for fracture-matrix imbibition by using self-similar solutions and pre-processing a 1D ordinary differential equation. This semi-analytical solution does not require any tuning parameters and is able to match the fine-grid reference solution for a wide range of different fracture geometries, fluid and rock properties while adding very little overhead to the computation cost. We demonstrated that our new model is capable to capture the nonlinearity of the displacement curves, and compared it to several previous models.

ISBN: 9798494450906Subjects--Topical Terms:

3680519
Propagation.

Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation.
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245 1 0 $a Micromechanical Modeling of Rate-Dependent Multiphysics Fracture Propagation.
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300 $a 169 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-06, Section: B.
500 $a Advisor: Kovscek, Anthony;Tchelepi, Hamdi;Tartakovsky, Daniel .
502 $a Thesis (Ph.D.)--Stanford University, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a Rate-dependent behavior associated with deformation and fracturing of materials poses significant challenges for modeling. In addition to the complications of the viscoelastic response, the speed of fracture propagation reflects micromechanical mechanisms in the fracture process zone(FPZ). In order to represent these complicated behaviors, a thermodynamically consistent, rate-dependent fracture model is required. Based on rigorous thermodynamic principles, we derive a rate-dependent phase-field mechanical model coupled with single-phase fluid flow in both the matrix and the fracture. The model is guaranteed to satisfy energy conservation during fracture propagation. The proposed phase-field model is tested against several benchmark problems on solid-fluid coupling, fluid-driven fracture propagation and rate-dependent viscoelastic deformation. The model serves as a strong basis for investigating rate-dependent fracturing experiments and for making predictions of material behaviors under new conditions.With the developed numerical model, we are able to apply our simulator to a wide range of mechanical problems. Specifically, we are interested in addressing the rate-dependent deformation and fracturing in shales. Shale gas plays an important role in addressing rising global energy demand and national energy security. To date, hydraulic fracturing with slickwater treatment continues to be the most widely-used stimulation method for shale gas reservoirs. A number of alternatives have been explored including fracturing using nonaqueous fluids, such as supercritial carbon dioxide (sc-CO2), to reduce water consumption and circumvent production inefficiency caused by water blocking and clay swelling. Experimental studies have compared the behavior of CO2 to water injection.Due to differences in experimental setup and core sample preparation, inconsistent or even apparently contradictory conclusions have resulted. In this study, we propose a numerical model capable of reproducing the hydraulic fracturing experiments found in the literature and we investigate the impact of various material and fluid properties on the resulting fracture. Our finite element numerical model is adapted from a rate-dependent phasefield fracture model developed separately. Most importantly, we studied the effect of fluid properties and confining condition on the breakdown pressure, and how the topology of the resulting fracture plane changes. We showed that sc-CO2 injection can result in breakdown pressure about 1.75 times that of water under strict sealing and confining conditions in the laboratory for the shale studied. sc-CO2 also produces fast-propagating fractures with less influence of the bedding plane on fracture topology. Our model offers a straightforward explanation and reconciliation of existing experimental observations, as well as a means to extrapolate to unseen conditions.In addition to the macroscopic fractures created during hydraulic fracturing, microfractures can be induced during shale maturation. Recent studies suggested the importance of microfracture networks to recovery that connect localized zones with large organic content to the inorganic matrix. We applied our numerical model to a shale analog system and performed joint modeling and experimental study to examine the onset, formation, and evolution of microfracture networks as shale matures. Both the stress field and fractures are simulated and imaged. The experimental setup was fitted to utilize photoelasticity principles coupled with birefringence properties of gelatin to explore visually the stress field of the gelatin as the fracture network developed. Stress optics image analysis and linear elastic fracture mechanics (LEFM) principles for crack propagation were used to monitor fracture growth for each gelatin type. Observed and simulated responses suggest gas diffusion within and deformation of the gelatin matrix as predominant mechanisms for energy dissipation depending on gelatin strength. LEFM, an experimental estimation of principal stress development with fracture growth, at different stages was determined for each gelatin rheology. The interplay of gas diffusion and material deformation determines the resulting fracture density and pattern.For typical applications in subsurface engineering, the domain of interest is often orders of magnitude larger than the underlying fracture networks. Instead of developing a sophisticated phenomenological model, a constitutive modeling approach called multi-scale constitutive model has become increasing popular in the computational mechanics community. Multi-scale constitutive models provide a convenient way of describing complex material dynamics with varying length scales without explicitly constructing a phenomenological model. For certain materials, the parameter space is extremely large thanks to the multi-scale nature of the micro-structure. Take shale as an example, the heterogeneity of organic and inorganic compounded with convoluted layering and embedding structures could range from micron scale to centimeter scale. We developed a variational multi-scale constitutive model for rate-dependent fractured media. By assuming scale separation, we model the homogenized stress-strain response in a representative elementary volume (REV) and upscale the resulting stress tensor and material tangent to macroscopic domain. We introduced basic implementation workflow in an FEM simulator framework. We then validated our multi-scale constitutive model against several benchmark tests. Finally, we demonstrated the effectiveness of the multi-scale model in a real-world fracturing experiment on shale.In terms of fluid flow in fractured media, naturally occurring fracture networks often exhibit complex topology on various scales. And it is often intractable to model simultaneously their effects across different scales. Assuming scale separation, Dual-Porosity Dual-Permeability (DPDK) models can be used to simulate the fluid flow in the naturally fractured porous media. However, when applied to formations with highly nonlinear flow properties, existing models often fail to deliver accurate results within a reasonable computation budget. In this work, we present a novel semi-analytical solution for fracture-matrix imbibition by using self-similar solutions and pre-processing a 1D ordinary differential equation. This semi-analytical solution does not require any tuning parameters and is able to match the fine-grid reference solution for a wide range of different fracture geometries, fluid and rock properties while adding very little overhead to the computation cost. We demonstrated that our new model is capable to capture the nonlinearity of the displacement curves, and compared it to several previous models.
590 $a School code: 0212.
650 4 $a Propagation. $3 3680519
650 4 $a Pressure distribution. $3 3564852
650 4 $a Hydrocarbons. $3 697428
650 4 $a Scale models. $3 3683930
650 4 $a Sensitivity analysis. $3 3560752
650 4 $a Viscoelasticity. $3 718183
650 4 $a Permeability. $3 915594
650 4 $a Normal distribution. $3 3561025
650 4 $a Carbon dioxide. $3 587886
650 4 $a Physics. $3 516296
650 4 $a Statistics. $3 517247
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710 2 $a Stanford University. $3 754827
773 0 $t Dissertations Abstracts International $g 83-06B.
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