An efficient numerical simulator for geothermal simulation: A benchmark study

Wang, Yang; Voskov, Denis; Khait, Mark; Bruhn, David

doi:10.1016/j.apenergy.2020.114693

Cited by 68 publications

(32 citation statements)

References 20 publications

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“…Fluid and temperature simulations were done using the Delft Advanced Research Terra Simulator (DARTS), which is a python/Cþþ based simulator capable of simulating high-enthalpy (water and steam) systems (Khait, 2019;Wang et al, 2020) (Fig. 4; Table 1).…”

Section: Fluid-flow/temperature Modellingmentioning

confidence: 99%

“…4; Table 1). DARTS assumes that the two-phase thermal system can be described by mass and energy conservation equations (Wang et al, 2020):…”

Section: Fluid-flow/temperature Modellingmentioning

confidence: 99%

“…Furthermore, to simplify the models, we upscaled the DFNs to an effective media, and this implies that our models cannot properly replicate effects caused by strong permeability contrasts between the fracture-and surrounding rock matrix (e.g. only production from the connected fracture network or early water breakthrough) (Lepillier et al, 2019;Wang et al, 2020). The presented workflow also accounts for elastic rock properties and local stress perturbations, both of which are known to be important when predicting fracture network characteristics in the subsurface (e.g.…”

Section: Potential Improvements To the Modelling Workflowmentioning

confidence: 99%

“…Hooker et al, 2014) (4) using explicitly modelled faults and fractures rather than upscaled cells in future fluid-flow/temperature simulations (e.g. Boersma et al, 2019;Lepillier et al, 2019;Wang et al, 2020), ( 5) different fracture population methodologies (e.g. stressbased fracture intensity drivers (Maerten et al, 2006(Maerten et al, , 2016(Maerten et al, , 2019), ( 6) creating 3D rather than 2D reservoir models and DFNs, and (7) optimising the location of the injector and production wells whilst accounting for geological uncertainties (e.g.…”

Section: Potential Improvements To the Modelling Workflowmentioning

confidence: 99%

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The impact of natural fractures on heat extraction from tight Triassic sandstones in the West Netherlands Basin: a case study combining well, seismic and numerical data

Boersma

Bruna

Hoop

et al. 2021

Netherlands Journal of Geosciences

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The positive impact that natural fractures can have on geothermal heat production from low-permeability reservoirs has become increasingly recognised and proven by subsurface case studies. In this study, we assess the potential impact of natural fractures on heat extraction from the tight Lower Buntsandstein Subgroup targeted by the recently drilled NLW-GT-01 well (West Netherlands Basin (WNB)). We integrate: (1) reservoir property characterisation using petrophysical analysis and geostatistical inversion, (2) image-log and core interpretation, (3) large-scale seismic fault extraction and characterisation, (4) Discrete Fracture Network (DFN) modelling and permeability upscaling, and (5) fluid-flow and temperature modelling. First, the results of the petrophysical analysis and geostatistical inversion indicate that the Volpriehausen has almost no intrinsic porosity or permeability in the rock volume surrounding the NLW-GT-01 well. The Detfurth and Hardegsen sandstones show better reservoir properties. Second, the image-log interpretation shows predominately NW–SE-orientated fractures, which are hydraulically conductive and show log-normal and negative-power-law behaviour for their length and aperture, respectively. Third, the faults extracted from the seismic data have four different orientations: NW–SE, N–S, NE–SW and E–W, with faults in proximity to the NLW-GT-01 having a similar strike to the observed fractures. Fourth, inspection of the reservoir-scale 2D DFNs, upscaled permeability models and fluid-flow/temperature simulations indicates that these potentially open natural fractures significantly enhance the effective permeability and heat production of the normally tight reservoir volume. However, our modelling results also show that when the natural fractures are closed, production values are negligible. Furthermore, because active well tests were not performed prior to the abandonment of the Triassic formations targeted by the NLW-GT-01, no conclusive data exist on whether the observed natural fractures are connected and hydraulically conductive under subsurface conditions. Therefore, based on the presented findings and remaining uncertainties, we propose that measures which can test the potential of fracture-enhanced permeability under subsurface conditions should become standard procedure in projects targeting deep and potentially fractured geothermal reservoirs.

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Section: Fluid-flow/temperature Modellingmentioning

confidence: 99%

“…4; Table 1). DARTS assumes that the two-phase thermal system can be described by mass and energy conservation equations (Wang et al, 2020):…”

Section: Fluid-flow/temperature Modellingmentioning

confidence: 99%

Section: Potential Improvements To the Modelling Workflowmentioning

confidence: 99%

Section: Potential Improvements To the Modelling Workflowmentioning

confidence: 99%

See 2 more Smart Citations

The impact of natural fractures on heat extraction from tight Triassic sandstones in the West Netherlands Basin: a case study combining well, seismic and numerical data

Boersma

Bruna

Hoop

et al. 2021

Netherlands Journal of Geosciences

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“…The Delft Advanced Research Terra Simulator (DARTS) is a Python and C++ based dynamic reservoir simulator, developed at Delft University of Technology (Khait 2019;) and has demonstrated fast and accurate performance for geothermal applications (Wang et al 2019(Wang et al , 2020. It is based on the framework of Operator-Based Linearization (OBL) (Voskov 2017), which makes it fit for the simulation of complex multiphase flow and transport systems (Khait 2019;Khait and Voskov 2018b).…”

Section: Delft Advanced Research Terra Simulator (Darts)mentioning

confidence: 99%

Economic and fault stability analysis of geothermal field development in direct-use hydrothermal reservoirs

2021

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The installed capacity of geothermal systems for direct use of heat is increasing worldwide. As their number and density is increasing, the their interaction with subsurface faults becomes more important as they could lead to safety risks from induced seismicity. Assessment and management of such risks is essential for the further development and extension of geothermal energy for heating. At the same time, the economic output of geothermal systems can be marginal and is hence often supported by subsidy schemes. A combined assessment of fault stability and economic output could help operators to balance economic and safety aspects, but this is currently not common practice. In this study we present a methodology to assess field development plans based on fault stability and Net Present Value (NPV) using reservoir simulations of a fluvial, heterogeneous sandstone representative of the majority of direct-use Dutch geothermal systems. We find that the highest friction coefficient leading to exceedance of the Mohr–Coulomb failure criteria in this sandstone is 0.17; such values could be encountered in clay-rich fault gouges. Similar or lower fault permeability compared to the reservoir results in no changes and an increase respectively of both NPV and fault stability with larger Fault-to-Well Distance (FWD). Fault permeability higher than the reservoir permeability results in a minor increase in NPV with smaller FWD. Our results demonstrate that a combined analysis of thermal, hydraulic, mechanical and economic assessment supports a responsible and viable development of geothermal resources at a large scale. The importance of a high spatial density of supporting stress data will be essential for a better understanding and quantification of economic and fault stability effects of geothermal operations.

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An Advanced Discrete Fracture Methodology for Fast, Robust, and Accurate Simulation of Energy Production from Complex Fracture Networks

Hoop

Voskov

Bertotti

et al. 2022

Preprint

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Fracture networks are abundant in subsurface applications (e.g., geothermal energy production, CO 2 sequestration). Fractured reservoirs often have a very complex structure, making modeling flow and transport in such networks slow and unstable. Consequently, this limits our ability to perform uncertainty quantification and increases development costs and environmental risks. This study provides an advanced methodology for simulation based on Discrete Fracture Model approach. The preprocessing framework results in a fully conformal, uniformly distributed grid for realistic 2D fracture networks at a required level of precision. The simplified geometry and topology of the resulting network are compared with input (i.e., unchanged) data to evaluate the preprocessing influence. The resulting mesh-related parameters, such as volume distributions and orthogonality of control volume connections, are analyzed. Furthermore, changes in fluid-flow response related to preprocessing are evaluated using a high-enthalpy two-phase flow geothermal simulator. The simplified topology directly improves meshing results and, consequently, the accuracy and efficiency of numerical simulation. The main novelty of this work is the introduction of an automatic preprocessing framework allowing us to simplify the fracture network down to required level of complexity and addition of a fracture aperture correction capable of handling heterogeneous aperture distributions, low connectivity fracture networks, and sealing fractures. The graph-based framework is fully open-source and explicitly resolves small-angle intersections within the fracture network. A rigorous analysis of changes in the static and dynamic impact of the preprocessing algorithm demonstrates that explicit fracture representation can be computationally efficient, enabling their use in large-scale uncertainty quantification studies.Plain Language Summary Fractured rocks occur naturally and are abundant in the Earth's subsurface, especially in rocks that host a variety of resources, from geothermal energy to clean water. Modeling fluid flow in such systems is complex and time-consuming, increasing environmental and economic risks. We attempt to tackle this problem by introducing an advanced modeling technique that simplifies the fractures' representation while maintaining the main characteristics. The method's performance is analyzed based on changes in the geometry of the fractures and fluid-flow patterns. The framework manages to significantly speed up the required time for fluid flow calculations while remaining close to the highfidelity solution (i.e., solution of unchanged fracture configuration). Because most of the parameters in subsurface-related energy applications are uncertain, many simulations have to be carried out to quantify these uncertainties. Since our framework reduces the computational time, more simulations could be executed, reducing the risks associated with the development of subsurface energy resources.

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An efficient numerical simulator for geothermal simulation: A benchmark study

Cited by 68 publications

References 20 publications

The impact of natural fractures on heat extraction from tight Triassic sandstones in the West Netherlands Basin: a case study combining well, seismic and numerical data

The impact of natural fractures on heat extraction from tight Triassic sandstones in the West Netherlands Basin: a case study combining well, seismic and numerical data

Economic and fault stability analysis of geothermal field development in direct-use hydrothermal reservoirs

An Advanced Discrete Fracture Methodology for Fast, Robust, and Accurate Simulation of Energy Production from Complex Fracture Networks

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