Saturated oil viscosity

Beggs & Robinson

The Beggs & Robinson correlation estimates the viscosity of saturated oil containing dissolved gas. It is based on data from North American crude oils and involves two steps: calculating the viscosity of dead oil, and then applying a correction for the presence of dissolved gas. The correlation is known for its simplicity and reliable accuracy for light and medium oils (20–45 °API). 
Recommended applicability range:

• Oil density (API Gravity): 16 – 58 °API
• Temperature: 70 – 295 °F
• Viscosity: 0.5 – 50 cP
• Solution gas–oil ratio (GOR): 20 – 2000 SCF/STB

Beal

The Beal correlation is one of the earliest fundamental methods for calculating the viscosity of saturated oil. It was developed based on experimental data from North American crude oils. The method defines viscosity as a function of bubble point pressure, temperature, and oil density using a set of empirical coefficients. Its key feature is simplicity and reliability under standard conditions, although additional adjustments may be required for heavy oils or extreme conditions. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 100 – 220 °F
• Viscosity: 0.5 – 50 cP

Bergman

The Bergman correlation (2004) is designed to estimate the viscosity of saturated oil based on the viscosity of dead oil and solution gas-oil ratio. It is most suitable for medium-density oils with moderate gas content but may introduce errors for heavy oils, condensates, or extreme gas-oil ratios. The formula is simple to apply but should not replace laboratory measurements when working with non-standard fluids. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 70 – 300 °F
• Viscosity: 0.5 – 50 cP
• Gas-oil ratio: 50 – 2000 SCF/STB

De Ghetto

The De Ghetto empirical correlation was developed based on an extensive analysis of experimental data for saturated oil. It was primarily designed for application to Brazilian oilfield conditions but has demonstrated good versatility and applicability beyond this region. 
Recommended applicability range:

• Oil density (API Gravity): 16 – 45 °API
• Temperature: 20 – 260 °F
• Viscosity: 0.1 – 1000 cP
• Gas-oil ratio: 10 – 2000 SCF/STB

De Ghetto Agip

The De Ghetto correlation, developed by Agip, is designed to estimate the viscosity of saturated oil based on its density, gas-oil ratio, and temperature. It is derived from a statistical analysis of various oil types, including heavy and highly viscous oils, making it more versatile than many other methods. The formula includes correction factors to account for the influence of oil density and dissolved gas content, allowing for application across a wide range of conditions. 
Recommended applicability range:

• Oil density (API Gravity): 6 – 50 °API
• Temperature: 80 – 300 °F
• Viscosity: 0.5 – 1000 cP
• Gas-oil ratio: 50 – 2000 SCF/STB

Petrosky

The Petrosky correlation was specifically developed for Gulf of Mexico crude oils, considering the high temperatures and pressures typical of deepwater reservoirs. It provides high accuracy for light to medium oils (20–40 °API) and includes a correction for gas-oil ratio. Compared to Beggs & Robinson, it demonstrates 10–15% better accuracy for Gulf of Mexico conditions. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 80 – 320 °F
• Viscosity: 0.5 – 50 cP
• Gas-oil ratio: 100 – 2500 SCF/STB

Egbogah

The Egbogah correlation was specifically developed for heavy and bituminous oils (5–25 °API). It accounts for the effects of gas-oil ratio, dead oil viscosity, and temperature. This model is especially useful for "cold" reservoirs and crudes with high asphaltene content. It is not applicable to light oils. 
Recommended applicability range:

• Oil density (API Gravity): 5 – 25 °API
• Temperature: 60 – 250 °F
• Viscosity: 50 – 50,000 cP
• Gas-oil ratio: 20 – 800 SCF/STB

Chu & Connally

The Chu & Connally correlation estimates the viscosity of saturated oil based on dead oil viscosity and gas-oil ratio. It is especially useful for light and medium oils and is widely used in engineering calculations. The model accounts for the nonlinear effect of dissolved gas on oil viscosity, but it is less accurate for heavy oils (API < 20) and highly viscous fluids (>50 cP). 
Recommended applicability range:

• Oil density (API Gravity): 15 – 50 °API
• Temperature: 70 – 295 °F
• Viscosity: 0.5 – 50 cP
• Gas-oil ratio: 50 – 3500 SCF/STB

Standing

Standing proposed an empirical correlation to estimate the viscosity of saturated oil based on data from California oil fields. The method relates viscosity to pressure, temperature, gas-oil ratio, and oil density. The correlation is simple to apply and suitable for "Black oil" models without significant amounts of non-hydrocarbon components. At high gas-oil ratios, it may overestimate viscosity. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 100 – 250 °F
• Pressure: < 5000 psi
• Gas-oil ratio: 90 – 1500 SCF/STB

Kartotomojo & Schmidt

The early version of the Kartotomojo & Schmidt (1991) correlation was developed as an improvement over the Standing and Beggs & Robinson models. It provides more accurate viscosity predictions for a wide range of crude oils, especially for fields in Southeast Asia. This version of the correlation uses a power-law dependency on gas-oil ratio and dead oil viscosity, delivering better accuracy for heavy and high-viscosity oils. 
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Temperature: 100 – 300 °F
• Viscosity: 1 – 5000 cP
• Gas-oil ratio: 50 – 2500 SCF/STB

Khan

The Khan correlation was developed for predicting saturated oil viscosity by accounting for the effects of gas-oil ratio, temperature, and oil density. It is particularly useful across a wide range of oil properties, including heavy fluids. Its main advantage is versatility, as it is applicable to light, medium, and heavy crude oils. Additionally, the model accounts for the significant impact of high gas-oil ratios on viscosity. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 100 – 300 °F
• Viscosity: 1 – 1000 cP
• Gas-oil ratio: 200 – 2500 SCF/STB

Glaso

Glaso (1980) proposed a generalized correlation for estimating oil viscosity, taking into account gas-oil ratio, oil and gas density, and temperature. It is better suited for light and medium crude oils than Standing’s method, especially under high gas-oil ratios. The correlation offers improved accuracy compared to older models due to the generalization of a large dataset. However, it is not recommended for heavy oils (API < 15°). 
Recommended applicability range:

• Oil density (API Gravity): 15 – 55 °API
• Temperature: 70 – 295 °F
• Gas-oil ratio: 50 – 3500 SCF/STB