McCain Oil density correlation

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Brief

McCain is an empirical correlation for the oil density published in 1995 [1].

Oil density in the PVT Tool

Math & Physics

Pseudoliquid density:

\rho_{po} = 52.8 - 0.01 R_{sb}

Apparent liquid density:

\rho_a = -49.8930 + 85.0149\ SG_g - 3.70373\ SG_g\ \rho_{po} + 0.0479818\ SG_g\ \rho_{po}^2 + 2.98914\ \rho_{po} - 0.0356888\ \rho_{po}^2

Next pseudoliquid density:

\rho_{po} = \frac{R_s\ SG_g + 4,600\ SG_o}{73.71+R_s\ SG_g\ / \rho_a}[2]

Iterate until pseudoliquid densities are equal.

Next adjust density to the pressure of interest:

\rho_{bs} = \rho_{po} + \triangle \rho_P

where

\triangle \rho_{P} = \left ( 0.617 + 16.181 \times 10^{-0.0425\ \rho_{po}} \right) \frac{P}{1000} - 0.01 \left ( 0.299 + 263 \times 10^{-0.0603\ \rho_{po}}\right)\ \left (\frac{P}{1000}\right)^2

Adjust density to the temperature of interest:

\rho_{o} = \rho_{bs} + \triangle \rho_T

where

\triangle \rho_T = (0.00302 + 1.505\ \rho_{bs}^{-0.951}) (T - 60)^{0.938} - (0.0216 - 0.0233\ (10^{-0.0161\ \rho_{bs}})) (T - 60)^{0.475}

Adjust density above the bubble point pressure:

\rho_{o} = \rho_{b}\ e^{c_o\ (P - P_b)}

Discussion

Application range

Description of the Data Used[1]:

  133 \le P_b \le 6,700
  77 \le T \le 327
  18 \le R_{sb} \le 1,975
  0.76 \le SG_o \le 0.95
  0.556 \le SG_g \le 1.237
  31.3 \le \rho_{ob} \le 55.77

Number of data sets = 684

Nomenclature

 c_o = oil compressibility, 1/psia
 P = pressure, psia
 R_s = solution gas-oil ratio, scf/stb
 SG_g = gas specific gravity, dimensionless
 SG_o = oil specific gravity, dimensionless
 T = temperature, °F
 \rho_{a} = apparent density of surface gas if it were a liquid, lbm/ft3
 \rho_{bs} = liquid density at reservoir pressure and 60°F, lbm/ft3
 \rho_o = oil density, lbm/ft3
 \rho_{po} = pseudoliquid formed by recombination of surface gas and liquid at standard conditions, lbm/ft3
 \triangle \rho_{P} = adjustment to liquid density due to pressure, lbm/ft3
 \triangle \rho_{T} = adjustment to liquid density due to temperature, lbm/ft3

Subscripts

b - bubble point
g - gas
o - oil

References

  1. 1.0 1.1 McCain, W.D. Jr.; Hill, N. C. (1995). "Correlations for Liquid Densities and Evolved Gas Specific Gravities for Black Oils During Pressure Depletion"Free registration required. Society of Petroleum Engineers (SPE-30773-MS). 
  2. McCain, W.D. Jr. (1990). Properties of Petroleum Fluids (2 ed.). Oklahoma: PennWell Corp. ISBN 978-0878143351.