Discrete fracture network modelling applied to groundwater resource exploitation in southwest Ireland

Jones, Mark; Pringle, Alec B.; Fulton, Iain M.; O’Neill, Shane

doi:10.1144/gsl.sp.1999.155.01.08

Cited by 8 publications

(8 citation statements)

References 10 publications

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“…Models of ground water flow and solute transport through fractured rock typically represent fractures as 3D, discrete planar features. These models have been used for development of well fields in fractured media (Jones et al 1999), oil and gas reservoir engineering (Dershowitz et al 1994), and evaluation of sites for disposal of high‐level nuclear waste (Anna 1998). They are well suited for simulating flow through fractured rocks because of the large contrast in K between fractures and the rock matrix and the low density of fractures encountered in rock.…”

Section: Model Descriptionsmentioning

confidence: 99%

Simulating Conservative Tracers in Fractured Till under Realistic Timescales

Helmke¹,

Simpkins

Horton

2005

Groundwater

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Discrete-fracture and dual-porosity models are infrequently used to simulate solute transport through fractured unconsolidated deposits, despite their more common application in fractured rock where distinct flow regimes are hypothesized. In this study, we apply four fracture transport models--the mobile-immobile model (MIM), parallel-plate discrete-fracture model (PDFM), and stochastic and deterministic discrete-fracture models (DFMs)--to demonstrate their utility for simulating solute transport through fractured till. Model results were compared to breakthrough curves (BTCs) for the conservative tracers potassium bromide (KBr), pentafluorobenzoic acid (PFBA), and 1,4-piperazinediethanesulfonic acid (PIPES) in a large-diameter column of fractured till. Input parameters were determined from independent field and laboratory methods. Predictions of Br BTCs were not significantly different among models; however, the stochastic and deterministic DFMs were more accurate than the MIM or PDFM when predicting PFBA and PIPES BTCs. DFMs may be more applicable than the MIM for tracers with small effective diffusion coefficients (De) or for short timescales due to differences in how these models simulate diffusion or incorporate heterogeneities by their fracture networks. At large scales of investigation, the more computationally efficient MIM and PDFM may be more practical to implement than the three-dimensional DFMs, or a combination of model approaches could be employed. Regardless of the modeling approach used, fractures should be incorporated routinely into solute transport models in glaciated terrain.

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Section: Model Descriptionsmentioning

confidence: 99%

Simulating Conservative Tracers in Fractured Till under Realistic Timescales

Helmke¹,

Simpkins

Horton

2005

Groundwater

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“…Great advances have been made in recent years with this concept, through numerical models to solve transport equations that explicitly account for advection, diffusion, dispersion and different fluid flux rates (e.g. Baumgartner & Rumble 1988;Bickle & Baker 1990;Bickle & McKenzie 1987;Cartwright 1997;Dipple & Ferry 1992;Fein et al 1994;Gerdes & Valley 1994;Jones et al 1999;Norton 1988;Norton & Taylor 1979;Wagner et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of fluid flow and fluid–rock interaction in fossil metamorphic hydrothermal systems inferred from vein–wallrock patterns, geometry and microstructure

2001

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Comparison of mass transfer patterns, geometry and microstructures developed within and around veins allows the interpretation of processes of fluid flow during deformation, metamorphism and mineralization. A classification of vein types based on the degree of interaction with wallrock (using petrological, geochemical or isotopic indicators) can be used to identify a range of processes, from closed system behaviour in which the vein mass is derived from local wallrock, through to open system behaviour in which the vein mass is derived externally. Microstructural characteristics, such as wallrock selvages, multiple growth events recorded by vein seams and vein crystal morphology, also help to constrain mass transfer patterns during vein formation. We present a range of processes for vein formation, including: (i) the formation of closed system fibrous veins by dissolution–precipitation creep, including varieties in which tensile failure is not required; (ii) pressure‐ or kinetically dependent closed system segregation veins in which transfer of soluble components from wallrock to vein leaves behind a residual selvage; (iii) similar vein–selvage patterning, but with mass imbalances between vein and wallrock requiring fluid advection through both interconnected fracture networks and in the surrounding permeable rock; and (iv) the proposed formation of veins by fluid ascent in mobile hydrofractures, in which isotopic or chemical disequilibrium within and around the vein suggests that the crack and fluid within it moved essentially as one. The postulate of rapid fluid and mass transfer via such mobile hydrofractures has implications for the release of volatiles from metamorphic terrains. Also, consideration of a broad range of possible vein‐forming mechanisms is highly desirable when dealing with mineral deposits found in deformed, metamorphosed rocks, because closed system veining may produce patterns that, if erroneously recognized as being open systems, could lead to false interpretations of the role of tectonic fracturing in ore genesis.

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“…Instead the model that is developed will attempt to capture the most permeable part of the fracture network that actually flows. This generally represents approximately 10% of the geologically identified fractures (Jones et aL 1999). The initial DFN model provides a static representation of reservoir fractures; whereas, the conversion of the fracture elements to a complex finite element flow grid allows the simulation of pressure transients through the fracture network.…”

Section: Generalized Dfn Work Flowmentioning

confidence: 99%

Integrating discrete fracture network models and pressure transient data for testing conceptual fracture models of the Valhall chalk reservoir, Norwegian North Sea

Rogers

Enachescu²,

Trice

et al. 2007

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The Valhall Field is an Upper Cretaceous chalk reservoir located in the Central Graben area of the North Sea with production coming from the fractured Tor and Hod formations. Well tests and production history indicate that these formations are highly heterogeneous and that significant fluid flow occurs through both the matrix and fracture system. However there remained significant uncertainty about the specific controls and location of the main productivity conduits and how they would influence sweep efficiency during planned water flood. To address these uncertainties a range of possible conceptual fracture models were considered with respect to controls on major flow within the reservoir. Analysis indicated that the reservoir is dominated by a connected series of seismic scale faults acting as major flow conduits with smaller fractures providing a less significant enhancement to matrix permeability. A key input to this study was the examination of over 80 well tests. Simulation of a number of key well tests using a simple discrete fracture network model comprising a connected fault network and pseudo-matrix layer was able to reproduce the majority of the observed pressure derivative shapes. This gave some confidence to the understanding of major reservoir flow paths as well as providing calibrated fault properties for direct inclusion within the simulation model.

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Discrete fracture network modelling applied to groundwater resource exploitation in southwest Ireland

Cited by 8 publications

References 10 publications

Simulating Conservative Tracers in Fractured Till under Realistic Timescales

Simulating Conservative Tracers in Fractured Till under Realistic Timescales

Mechanisms of fluid flow and fluid–rock interaction in fossil metamorphic hydrothermal systems inferred from vein–wallrock patterns, geometry and microstructure

Integrating discrete fracture network models and pressure transient data for testing conceptual fracture models of the Valhall chalk reservoir, Norwegian North Sea

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