PGE 312_Spring10_Solution_HW9

# Gas specific gravity γ g 0872 stock tank oil gravity

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??? Gas specific gravity, γ g = 0.872 Stock tank oil gravity = 40.2 o API Initial reservoir pressure = 2880psia Solution: Dead oil viscosity, μ oD = 1.76cp from Fig. 11-13 (using 40.2 o API and 142 o F) Above the bubble point pressure the solution gas oil ratio is equal to the producing gas-oil ratio. Therefore, R s = R p = 370 ??? ??? Viscosity of saturated oil, μ ob = 0.62cp from Fig. 11-14 (using μ oD = 1.76cp and R s = 370 ??? ??? ) The viscosity at pressure 2880psia (p>p b ) is obtained from Fig.11-15 (using μ ob = 0.62cp, p b =1250psia and p=2880psia) as, μ o = 0.79cp Problem 11-33 Parachor of n-octane = 351.5 ρ L = 0.59 ? ?? ρ g = 0.01 ? ?? Molecular weight of n-octane = 114 g/gmol 𝜎 = ? 𝜌 ? −𝜌 ? ? = 351.5 0.59 0.02 114.231 4 = 9.46 ???? ?? Problem 11-34 Reservoir Pressure = 1500psia

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11 Reservoir Temperature = 600 o R Component Liquid mole fraction x j Gas mole fraction y j M j x j M j y j M j Liquid density, 60 o F & 14.65 psia lb/cuft Liquid volume, 60 o F & 14.65 psia cu ft/STB Methane 0.3105 0.8742 16 4.97 13.99 19.98 0.2177 Ethane 0.0638 0.0634 30 1.91 1.90 29.34 0.0651 Propane 0.0646 0.0335 44 2.84 1.47 31.62 0.0898 i-butane 0.0146 0.0049 58 0.85 0.28 35.11 0.0242 n-butane 0.0478 0.0129 58 2.77 0.75 36.42 0.0761 i-pentane 0.0218 0.0035 72 1.57 0.25 38.96 0.0403 n-pentane 0.0255 0.0034 72 1.84 0.25 39.36 0.0467 Hexanes 0.0382 0.0026 86 3.29 0.22 41.40 0.0795 Heptanes Plus 0.4132 0.0016 202 83.47 0.32 53.11 1.5716 Total 1.0000 1.0000 102.89 19.42 2.2110 𝜌 ? = ?? ??? = 1500 17.68 0.85 10.732 600 = 5.3224 lb/cu ft. Therefore, 𝜌 ? = 0.086g/cc To calculate the apparent liquid densities of methane and ethane we use trial and error. We start with a trial value of 43.70 which corresponds to 0.70 g/cc. The values are shown in the above table. The first calculated pseudo-liquid density = 103.51 2.2110 = 46.81 lb/cu.ft. For a second trial value of 46.82 which corresponds to 0.75g/cc the values are tabulated below. Component Liquid mole fraction x j M j x j M j Liquid density, 60 o F & 14.65 psia lb/cuft Liquid volume, 60 o F & 14.65 psia cu ft/STB Methane 0.3105 16 4.97 21.21 0.2051 Ethane 0.0638 30 1.91 30.24 0.0632 Propane 0.0646 44 2.84 31.62 0.0898 i-butane 0.0146 58 0.85 35.11 0.0242 n-butane 0.0478 58 2.77 36.42 0.0761 i-pentane 0.0218 72 1.57 38.96 0.0403 n-pentane 0.0255 72 1.84 39.36 0.0467 Hexanes 0.0382 86 3.29 41.40 0.0795 Heptanes Plus 0.4132 202 83.47 53.11 1.5716 Total 1.0000 103.59 2.1965 The second calculated pseudo-liquid density = 103.51 2.1965 = 47.12 lb/cu.ft
12 Plotting the values we observe that the liquid relative density at standard conditions ρ o 47.1 lb/cu.ft Adjusting for isothermal compressibility at reservoir conditions from fig. 11-3 +0.55; Adjusting for isobaric expansion at reservoir conditions from fig 11-4 -2.75 Therefore, ρ o = 47.10 + 0.55 2.75 = 44.90 lb/cu.ft = 0.7192 g/cc Component x j y j P j 𝑷 𝒋 ( ? 𝒋 𝝆 ? ? ? − ? 𝒋 𝝆 ? ? ? ) Methane 0.3105 0.8742 77 -0.1185 Ethane 0.0638 0.0634 108 0.0223 Propane 0.0646 0.0335 150 0.0485 i-butane 0.0146 0.0049 181.5 0.0150 n-butane 0.0478 0.0129 189.9 0.0539 i-pentane 0.0218 0.0035 225.0 0.0311 n-pentane 0.0255 0.0034 231.5 0.0388 Hexanes 0.0382 0.0026 271 0.0693 Heptanes plus 0.4132 0.0016 575 *** 1.6879 Total 1.8408 *** from fig 11-18 σ = (1.8408) 4 = 11.48 dynes/cm
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