# Beggs and Robinson Oil Viscosity correlation

## Beggs and Robinson Oil Viscosity correlation

Beggs and Robinson is an empirical correlation for the oil viscosity published in 1975 [1].

Beggs and Robinson oil viscosity correlation in the PVT Software

## Math & Physics

$\mu_{od} = 10^x-1$

where:

$x = T^{-1.163} \times e^{(13.108-6.591/SG_{o})}$

Saturated oil viscosity (P < Pb):

$\mu_{os} = A \mu_{od}^B$

where:

$A = 10.715\ (R_s + 100)^{-0.515}$
$B = 5.44\ (R_s + 150)^{-0.338}$

Undersaturated oil viscosity (P > Pb):

$\mu_{o} = \mu_{os} (P/P_b)^m$[2]

where:

$m = 2.6\ P^{1.187}\ e^{(-11.513-8.98 \times 10^{-5}\ P)}$

## Example. Calculation of the oil viscosity

Example source [3]

### Input data

$T$ = 137 F°
$SG_o$ = 0.922 or 22 API
$R_s$ = 90 scf/stb

Calculate the saturated oil viscosity?

### Solution

x = 1.2658

$\mu_{od}$ = 17.44 cP

A = 0.719 B = 0.853

$\mu_o$ = 8.24 cP

The solution is available in the online PVT calculator software model at www.pengtools.com

## Application range

Description of the Data Used[1]:

$20 \le R_s \le 2,070$
$0.75 \le SG_o \le 0.96$
$0 \le P \le 5250$
$70 \le T \le 295$

Number of oil systems = 600
Number of dead oil observations = 460
Number of live oil observations = 2,073

## Nomenclature

$A$ = coefficient
$B$ = coefficient
$m$ = coefficient
$P$ = pressure, psia
$R_s$ = solution gas-oil ratio, scf/stb
$SG_o$ = oil specific gravity, dimensionless
$T$ = temperature, °F
$x$ = coefficient
$\mu$ = viscosity, cP

b - bubble point