Comparative verification of discrete and smeared numerical approaches for the simulation of hydraulic fracturing

Yoshioka, Keita; Parisio, Francesco; Naumov, Dmitri; Lu, Renchao; Kolditz, Olaf; Nagel, Thomas

doi:10.1007/s13137-019-0126-6

Cited by 32 publications

(13 citation statements)

References 96 publications

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“…We perform hydromechanical finite element analyses using the open source platform OpenGeoSys (www.opengeosys.org). The fracture created in the first stage (stimulation) is modeled as a local enrichment at the element boundaries applying a Lower‐dimensional Interface Element (LIE) (Watanabe et al., 2012; Yoshioka, Parisio, Naumov, et al., 2019).…”

Section: Methodsmentioning

confidence: 99%

Modeling Fluid Reinjection Into an Enhanced Geothermal System

Parisio

Yoshioka

2020

Geophysical Research Letters

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The manuscript analyzes the stimulation for an Enhanced Geothermal System development in Acoculco, Mexico. Using an analytical penny-shaped hydraulic fracture model covering different propagation regimes, we computed the final fracture length and width by varying fluid properties with temperature. Our analysis indicates that for the given scenario, the fluid viscosity plays a minor role and instead flow rate and time of the stimulation are the controlling variables. We computed the fracture reopening as a consequence of water reinjection in the second stage of the stimulation through numerical computations based on the enriched discontinuity method. The computation shows that a single isolated fracture will not provide sufficient permeability, as the continuous injection will quickly fill and pressurize the crack. We demonstrate that the fracture needs to be connected to a permeable network to avoid excessive pressurization and achieve a commercially exploitable reservoir for Enhanced Geothermal System. Plain Language Summary At Acoculco, Mexico, the temperature of the rock at 2 km depth is approximately 300°C, which can be potentially exploited for the production of geothermal energy. To produce deep geothermal energy, water must be extracted from the rock, which is currently not possible in Acoculco because the host rock, a granite, is practically impermeable. A possible solution is to inject water into the rock formation and create one or multiple large fractures: Through the fractures, the fluid will be able to circulate and geothermal energy can be extracted. In this work, we show, through numerical calculations, that it will be relatively easy to create a large fracture by injecting high-pressure fluid, but if the fracture is not connected to a network of preexisting fractures, harvesting geothermal energy would be unlikely. The pressure will rapidly increase during the reinjection, which could trigger induced earthquakes if it exceeds sufficiently large values. We suggest instead to create fractures in multistage and maximize a chance of intersecting existing networks through zonal isolation.

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Section: Methodsmentioning

confidence: 99%

Modeling Fluid Reinjection Into an Enhanced Geothermal System

Parisio

Yoshioka

2020

Geophysical Research Letters

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“…Among its recent extensions are the implementation of numerical methods for the propagation of discontinuities, such as enriched finite element function spaces, non-local formulations and phase-field models for fracture (Watanabe, Wang, Taron, Görke, & Kolditz (2012); ; Yoshioka et al (2019)).…”

Section: Opengeosysmentioning

confidence: 99%

The MFrontGenericInterfaceSupport project

Helfer¹,

Bleyer²,

Frondelius³

et al. 2020

JOSS

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“…Considering hydraulic fracturing in the toughness dominated regime (Detournay, 2016), the pressure loss within the crack is negligible and p is spatially constant. Equation 11 is solved by the alternate minimization with respect to the displacement u and the phase‐field v with a constraint of prescribed time‐evolving fluid volume which must be equal to the crack volume, that is,

V_{inj} = V_{crack} = \int_{Ω} boldu \cdot \nabla d normald Ω

(Yoshioka et al., 2019). The minimization problem can be stated as

{false(boldu, v, p false)}^{*} = \underset{normalarg normalmin {scriptF}_{ℓ_{\int}} false(boldu, d, p false)}{true},

with the constrain

V_{inj} = \int_{Ω} boldu \cdot \nabla v normald Ω .

…”

Section: Variational Phase‐field Modelmentioning

confidence: 99%

Variational Phase‐Field Modeling of Hydraulic Fracture Interaction With Natural Fractures and Application to Enhanced Geothermal Systems

et al. 2020

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In every tight formation reservoir, natural fractures play an important role for mass and energy transport and stress distribution. Enhanced Geothermal Systems (EGS) make no exception, and stimulation aims at increasing the reservoir permeability to enhance fluid circulation and heat transport. EGS development relies upon the complex task of predicting accurate hydraulic fracture propagation pathway by taking into account reservoir heterogeneities and natural or preexisting fractures. In this contribution, we employ the variational phase‐field method, which handles hydraulic fracture initiation, propagation, and interaction with natural fractures and is tested under varying conditions of rock mechanical properties and natural fractures distributions. We run bidimensional finite element simulations employing the open‐source software OpenGeoSys and apply the model to simulate realistic stimulation scenarios, each one built from field data and considering complex natural fracture geometries in the order of a thousand of fractures. Key mechanical properties are derived from laboratory measurements on samples obtained in the field. Simulations results confirm the fundamental role played by natural fractures in stimulation's predictions, which is essential for developing successful EGS projects.

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Comparative verification of discrete and smeared numerical approaches for the simulation of hydraulic fracturing

Cited by 32 publications

References 96 publications

Modeling Fluid Reinjection Into an Enhanced Geothermal System

Modeling Fluid Reinjection Into an Enhanced Geothermal System

The MFrontGenericInterfaceSupport project

Variational Phase‐Field Modeling of Hydraulic Fracture Interaction With Natural Fractures and Application to Enhanced Geothermal Systems

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