1 Governing equations 2 In FEHM, the governing partial differential equations for mass and heat transfer are 3 discretized into a system of nonlinear algebraic equations, which are then solved using the 4 Newton-Raphson iteration method (a way to find successively better approximations to the roots 5 or zeroes of a real-valued function from an initial guess). In FEHM (as opposed to some other 6 multi-physics computer codes like TOUGH2 (Pruess et al. 2012), the Newton-Raphson 7 derivatives of the thermodynamic functions with respect to pressure and temperature are formed 8 analytically rather than numerically in order to achieve faster convergence of the nonlinear 9 system of equations (Zyvoloski 2007). FEHM equations of state are nonlinear because the 10 porosity, permeability, density, enthalpy and viscosity are strong functions of pressure and 11 temperature; in addition, relative permeabilities and capillary pressure can also be strong 12 functions of saturation, which varies significantly with temperature and pressure. Pressure and 13 temperature dependent behavior of density, enthalpy and viscosity are represented by rational 14 polynomials derived from National Bureau of Standards (NBS) steam table data (Zyvoloski et al. 15 1991). 16 All variables referenced in these equations are defined in Table 5. A more detailed 17 breakdown of the equation derivation may be found in Zyvoloski et al. (1999) and Keating ( 18 (2000). 19 20 21 22 23 Table 5. Variables used in FEHM governing equations Energy/mass/noncondensible gas accumulation terms (kg m-1 s-2)/ (kg m-3) / (kg m-3) Specific heat (m2 s-2 °C-1) R S Relative permeability Saturation T Temperature g flux vectors for energy/mass/noncondensible gas equation (kg s-3)/ (kg m-2 s-1)/ (kg m-2 s-1) gravitational acceleration (m s-2) t time h enthalpy (m2 s-2) v Velocity (m s-1) k intrinsic rock permeability (m2) Ο Porosity K Thermal conductivity (kg m T-1 s-3) ηvap,liq P Pressure (kg m-1 s-2) μ Mass fraction of vapor/liquid Viscosity (kg m-1 s1 ) Density Ae,m, gas Cp fe,m,gas Energy/mass/noncondensible gas source term (kg m- ρ 1 -3 s )/ (kg m-3 s-1)/ (kg m-3 s-1) Subscripts: gas = noncondensible gas, vap = vapor, liq = liquid, f = fracture, r = rock qe 24 25 Conservation of mass for water is ππ΄π 26 ππ‘ Μ ⋅ ππΜ + ππ = 0 +∇ (1) 27 where the mass per unit volume Am (a mass accumulation term) is a function of the porosity, the 28 saturation and the mass fraction of each phase: 29 30 31 π΄π = π(ππ£ππ ππ£ππ (1 − ππ£ππ ) + ππππ ππππ (1 − ππππ )) (2) ππΜ = (1 − ππ£ππ )ππ£ππ π£Μ π£ππ + (1 − ππππ )ππππ π£Μ πππ (3) the mass flux is 32 and sources/sinks of mass are contained in the term ππ . The total of all water flux through the 33 system, water accumulated in the system, and sources/sinks of water are assumed to equal zero. 34 Conservation of fluid-rock energy is 35 ππ΄π ππ‘ Μ ⋅ ππΜ + ππ = 0 +∇ (4) 36 where the energy per unit volume (energy accumulation term) Ae is a combination of energy 37 transferred by the rock itself, energy transferred by water vapor and energy transferred by liquid 38 water: π΄π = (1 − π)ππ πΆππ π + π(ππ£ππ ππ£ππ πΆππ£ππ π + ππππ ππππ πΆππππ π) 39 (5) 40 The energy flux, ππΜ , can be stated either as a sum of the products of density, specific enthalpy 41 and velocity of the vapor and liquid, or the product of the thermal conductivity and temperature 42 gradients: ππΜ = ππ£ππ βπ£ππ π£π£ππ + ππππ βπππ π£πππ = πΎπ»Μ π 43 44 The conservation of noncondensible gas is described by ππ΄πππ 45 46 ππ‘ 49 50 51 Μ + ππππ = 0 Μ ⋅ ππππ +∇ (7) where the accumulation term Agas is 47 48 (6) π΄πππ = π(ππ£ππ ππ£ππ ππ£ππ + ππππ ππππ ππππ ) (8) Μ = ππ£ππ ππ£ππ π£Μ π£ππ + ππππ ππππ π£Μ πππ ππππ (9) the gas flux is and the source and sink term qgas is ππππ = ππ£ππ ππ£ππ + ππππ ππππ (10) 52 It is assumed that Darcy’s law applies to the movement of each phase; in this formulation, the 53 hydraulic conductivity term is replaced by the quotient of the intrinsic and relative permeabilities 54 divided by the viscosity of the phase, and the hydraulic head term is replaced with the difference 55 between the pressure gradient and lithostatic gradient: 56 π£Μ π£ππ = − 57 π£Μ πππ = − ππ π£ππ ππ£ππ ππ πππ ππππ Μ ππ£ππ − ππ£ππ πΜ ) (∇ Μ ππππ − ππππ πΜ ) (∇ (11) (12) 58 By combining equations 1 – 10 with Darcy’s law (11 & 12), the full governing equations are 59 derived for mass, Μ ⋅ ((1 − ππ£ππ )Θππ£ππ ∇ Μ ππ£ππ ) − ∇ Μ ⋅ ((1 − ππππ )π©ππππ ∇ Μ ππππ ) + ππ + π π ((1 − −∇ ππ§ 60 ππ£ππ )π©ππ£ππ ππ£ππ + (1 − ππππ )π©ππππ ππππ ) + 61 62 63 ππ΄π ππ‘ =0 (13) Energy, Μ ⋅ (Θππ£ππ ∇ Μ ππ£ππ ) − ∇ Μ ⋅ (π©ππππ ∇ Μ ππππ ) + ππ + π π(π©ππ£ππ ππ£ππ + π©ππππ ππππ ) + ππ΄ππππ = 0 −∇ ππ§ ππ‘ 64 65 66 67 (14) and noncondensible gas: Μ ⋅ (ππ£ππ Θππ£ππ ∇ Μ ππ£ππ ) − ∇ Μ ⋅ (ππππ π©ππππ ∇ Μ ππππ ) + ∇ Μ ⋅ (π·π£π ∇ Μ ππ£ππ ) + πππππ + −∇ π π(ππ£ππ π©ππ£ππ ππ£ππ + ππππ π©ππππ ππππ ) + ππ§ ππ΄ππππ ππ‘ =0 (15) 68 Transmissibilities, a measure of how easily a given layer transmits water, are represented by Θ in 69 the equations and are given by ππ π£ππ ππ£ππ 70 π©ππ£ππ = 71 π©ππππ = 72 Θevap = hvap Θmvap (18) 73 π©ππππ = βπππ π©ππππ (19) 74 75 (16) ππ£ππ ππ πππ ππππ (17) ππππ The air/water diffusivity term Dva is given by 0 π·π£π = ππππ£ππ π·π£π ππ£ππ 0.101325 π+273.15 π π [ 273.15 ] (20) 76 where π is the tortuosity factor (for diffusion in porous media, a measure of how circuitous a 77 typical flow path is through a medium), D (standard conditions) = 2.4e-5 m2/s and m = 2.334 78 (Zyvoloski et al. 1997). Transmissibilities are given by ππ π£ππ ππ£ππ 79 π©ππ£ππ = 80 π©ππππ = 81 π©ππ£ππ = βπ£ππ π©ππ£ππ (23) 82 π©ππππ = βπππ π©ππππ (24) ππ£ππ ππ πππ ππππ ππππ (21) (22) 83 The nonisothermal multiphase transport model in FEHM is formed by equation 13, 14 and 15, 84 setting n = 0 in Equation 13 and leaving out Equation 15 in the pure-water model. 85 86 Relative permeability 87 In cases where the system being modeled in FEHM does not remain fully saturated, 88 FEHM is capable of calculating relative permeability using either a linear, Corey-Brooks 89 (Brooks and Corey 1964), or van Genuchten formulation (van Genuchten 1980). The linear 90 formulation used in this study depends only on the residual liquid and vapor saturations and was 91 chosen for simplicity. Linear functions for relative permeabilities of liquid (the wetting fluid, in 92 this case water) and vapor (the ‘nonwetting fluid’) are defined by the equations 0, 93 94 ππ −πππ π π = {π ππππ₯ −πππ π π£ = {π ππ ≤ πππ πππ < ππ < πππππ₯ 1, ππ ≥ πππππ₯ 0, ππ£ ≤ ππ£π ππ£ −ππ£π π£πππ₯ −ππ£π 1, ππ£π < ππ£ < ππ£πππ₯ (27) (28) ππ£ ≥ ππ£πππ₯ 95 where Sl and Sv are liquid and vapor saturations, Slr and Svr are the residual liquid and vapor 96 saturations, and Slmax and Svmax are the maximum liquid and vapor saturations. 97 98 99 Table 6. Material properties of andesite and dacite lavas and pyroclastic deposits Reference Location Sample size/type Rock type (Aizawa et al. 2009) Conceptual Unknown (Bartetzko et al. 2006) (Bernard et al. 2007) Undersea basin, PACMANUS field Mount Pelée Density (kg/m3) Porosity (φ) Permeability (m2) Sealing zone 0.01 3.00E-16 Unknown Basement 0.05 3.00E-16 Unknown Hydrothermal zone 0.1 3.00E-15 Unknown 0.3 1.00E-13 Unknown Fractured rock surrounding hydrothermal zone Conduit 0.1 1.00E-12 Unknown Fresh volcanic rock 0.3 1E-13 - 2E-14 Drill core Dacite 0.22 1.25E-17 Drill core Dacite 0.32 2.23E-17 Drill core Dacite 0.24 4.48E-17 Drill core Dacite 0.3 1.04E-16 Drill core Dacite 0.24 4.46E-16 Drill core Dacite 0.38 7.59E-16 Drill core Dacite 0.21 1.50E-15 Drill core Dacite 0.43 2.00E-15 Drill core Dacite 0.01 1.17E-14 Drill core Dacite 0.16 Drill core Dacite 0.17 Drill core Dacite 0.17 Drill core Dacite 0.2 Drill core Dacite 0.21 Drill core Dacite 0.22 Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample MB502 2700 0.038 1.00E-16 LPP Calebasse 2850 0.031 1.00E-15 LPP Plume 2890 0.035 1.00E-15 andesite, B&A flows 2780 0.099 1.00E-15 MB501 2740 0.102 1.00E-15 LPP Macouba 2760 0.134 1.00E-15 andesite dome 2720 0.098 2.00E-15 andesite, nuee ardente flows andesite, indurated block and ash flows andesite, indurated block and ash flows andesite, indurated block and ash flows andesite dome 2690 0.119 2.90E-15 2720 0.103 3.00E-15 2690 0.146 3.00E-15 2720 0.111 3.90E-15 2740 0.121 3.90E-15 andesite dome 2740 0.154 3.90E-15 Thermal conductivity (W/mK) Specific heat (J/kgK) Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample andesite, nuee ardente flows andesite, indurated block and ash flows andesite, indurated block and ash flows andesite, nuee ardente flows andesite, indurated block and ash flows andesite, nuee ardente flows andesite, nuee ardente flows andesite, nuee ardente flows andesite, indurated block and ash flows andesite, nuee ardente flows andesite, nuee ardente flows andesite, ash-andpumice flows andesite, nuee ardente flows andesite, nuee ardente flows andesite, ash-andpumice flows andesite, indurated block and ash flows andesite, indurated block and ash flows andesite, ash-andpumice flows andesite, indurated block and ash flows andesite, indurated block and ash flows andesite, nuee ardente flows andesite, scoria flows 2670 0.157 3.90E-15 2670 0.353 3.90E-15 2770 0.145 4.90E-15 2670 0.169 5.90E-15 2710 0.132 8.90E-15 2670 0.19 1.09E-14 2670 0.099 1.88E-14 2690 0.158 3.85E-14 2720 0.149 5.53E-14 0.312 5.92E-14 2670 0.174 1.09E-13 2650 0.574 1.44E-13 2700 0.197 1.67E-13 2690 0.146 2.04E-13 2630 0.547 2.07E-13 2620 0.213 2.27E-13 2760 0.24 2.54E-13 2650 0.536 4.25E-13 2620 0.232 5.54E-13 2630 0.321 5.70E-13 2670 0.415 6.70E-13 2810 0.28 1.03E-12 andesite, ash-andpumice flows andesite, nuee ardente flows andesite, nuee ardente flows andesite, scoria flows 2670 0.574 1.18E-12 2700 0.304 1.18E-12 2670 0.428 1.45E-12 2860 0.363 1.54E-12 andesite, nuee ardente flows andesite, indurated block and ash flows andesite, ash-andpumice flows andesite, nuee ardente flows andesite, indurated block and ash flows andesite, scoria flows 2690 0.251 1.58E-12 2680 0.305 1.77E-12 2670 0.578 2.05E-12 2680 0.274 2.91E-12 2710 0.289 5.06E-12 2840 0.352 5.69E-12 andesite, ash-andpumice flows andesite, block and ash flows andesite, block and ash flows 2650 0.617 7.66E-12 2710 0.328 1.02E-11 2670 0.408 3.44E-11 (Flint et al. 2006) Yucca Mountain (García et al. 1989) Los Azufres (Hicks et al. 2009) (Hurwitz et al. 2003) Soufriere Hills Cascades Hand sample Drill core andesite, ash-andpumice flows Pyroclastic unit 2670 0.585 1490 0.341 Drill core Pyroclastic unit 1600 0.322 Drill core Andesite 2053 0.02 1.05 Drill core Andesite 2737 0.24 2.34 Hand sample Conceptual Andesite 2600 0.2 2500 0.15 Conceptual Conduit (numerical model) Upper unit (numerical model) Basal unit 2500 0.01 Drill core Volcanic breccia 2400 0.15 Drill core Lava dike 2500 0.15 Drill core Lava dike 2600 0.15 Drill core Volcanic breccia 2500 0.3 Conceptual Lava flows and domes younger than 2.3 Ma Lava flows and minor pyroclastic rocks from 4-8 Ma Lava flows from 8 to 17 Ma Chiefly volcanic and volcaniclastic strata from 18-25 Ma Quartz-bearing ash flow tuff Dome rock Conceptual (Ikeda et al. 2008) (Ingebritsen et al. 1994) Unzen Cascades Conceptual Conceptual Conceptual Conceptual (Keating 2005) (Mueller et al. 2008) Mount St. Helens Unzen (Platz et al. 2012) (Reid 2004) Mt. Taranaki (Sammel et al. 1988) Newberry Cascades volcanoes Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Cores from clasts "typical of volcanic rocks" Conceptual 1.00E-10 2 2500 2 2.5 0.15 1.00E-14 1.55 0.1 5.00E-16 1.55 0.05 1.00E-16 1.65 0.05 1.00E-17 2 0.02 2.50E-14 2 2200 0.6 2.10E-14 0.9 1557 2200 0.25 1.00E-15 0.35 2036 2200 0.62 4.66E-14 0.35 2036 0.367 8.90E-14 0.475 1.47E-13 0.343 9.99E-13 Dacite, dome rock 0.349 3.41E-12 Dacite, dome rock 0.412 4.50E-12 14.47 918 2 1000 Pyroclastic flow deposits (substrate) Pyroclastic flow deposits Dacite, breadcrust bomb Dacite, breadcrust bomb Dacite, dome rock andesite dome 2555 Unknown 2650 6.80E-13 Fill 1E-14 - 5E-12 Conceptual Dikes and pipe 5.00E-15 Conceptual Flow 1 1E-15 - 1E-13 Conceptual Flow 2 1E-16 - 1E-14 Conceptual Flow 3 1E-17 - 1E-15 Conceptual Flow 4 5E-16 - 1E-13 Conceptual Flow 5 1E-18 - 1E-16 Conceptual Magma 1.00E-18 (Scheu et al. 2006) (Sekioka 1988) (Smith et al. 2001) (Watanabe et al. 2008) 100 101 102 103 104 Unzen Japanese geothermal fields Japanese geothermal fields Japanese geothermal fields Japanese geothermal fields Japanese geothermal fields Japanese geothermal fields Japanese geothermal fields Mount St. Helens Unzen Hand sample Hand sample Hand sample Hand sample Hand sample Hand sample Calculated Dacite 2490 0.041 Dacite 2420 0.073 Dacite 2280 0.12 Dacite 2180 0.163 Dacite 2100 0.193 Dacite 1930 0.259 Unknown 1.10E-12 2.04 Calculated Unknown 3.50E-13 2.33 Calculated Unknown 1.90E-12 3.43 Calculated Unknown 2.10E-12 2.87 Calculated Unknown 2.00E-12 1.49 Calculated Unknown 5.00E-14 0.93 Calculated Unknown 1.70E-12 1.65 Cores from spine samples Cores from spine samples Cores from spine samples Cores from spine samples Cores from spine samples Drill core dacite 2460 0.08 dacite 2390 0.095 dacite 2350 0.103 dacite 2260 0.121 dacite 2040 0.197 2410 0.08 1.00E-19 Drill core C1-5-7, Brecciated dacite C14, Dacite dike 2500 0.16 1.00E-19 Drill core C12, Volcanic breccia 2400 0.02 1.00E-17 Drill core C14-2, Dacite dike 2560 0.04 1.00E-17 Drill core C13, Dacite dike 2570 0.08 1.00E-17 105 106 107 Aizawa K, Ogawa Y, Ishido T (2009) Groundwater flow and hydrothermal systems within volcanic edifices: Delineation by electric self-potential and magnetotellurics. 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