Dead oil viscosity

Beal

The Beal correlation is one of the earliest but still widely used empirical models for estimating the viscosity of dead (degassed) oil. It is based on experimental data from North American crude oils. The correlation links viscosity with oil density and temperature. 
Recommended applicability range:

• Oil density (API Gravity): 14 – 40 °API
• Temperature: 100 – 220 °F
• Viscosity: 1 – 1000 cP (accuracy decreases for values > 100 cP)

Beggs & Robinson 

The Beggs & Robinson correlation estimates the viscosity of dead (degassed) oil based on oil density and temperature. It performs well for light and medium crude oils (above 22°API) but is less accurate for heavy oils (below 16°API) and highly viscous fluids. 
Recommended applicability range:

• Oil density (API Gravity): 16 – 58 °API
• Temperature: 70 – 295 °F
• Viscosity: 0.5 – 50 cP

Bergman

The Bergman correlation (2004) was developed specifically for heavy and bituminous crude oils, where classical models (such as Beggs & Robinson) often produce significant errors. This model is based on an extensive database that includes high-viscosity oil samples and provides more accurate predictions under complex conditions. 
Recommended applicability range:

• Oil density (API Gravity): 5 – 30 °API
• Temperature: 60 – 300 °F
• Viscosity: 10 – 20,000 cP

De Ghetto

The De Ghetto correlation was developed to estimate the viscosity of dead oil based on data from Mediterranean and Middle Eastern crude oils. It is particularly useful for medium and heavy oils, where many classical correlations (such as Beggs & Robinson) yield significant errors. The correlation is well-suited for high-sulfur crude oils. 
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Temperature: 80 – 300 °F
• Viscosity: 1 – 500 cP

De Ghetto (Agip)

The De Ghetto et al. correlation (developed for Agip) is designed to estimate the viscosity of dead oil, with a focus on heavy and bituminous crudes. It is based on a comprehensive database including samples from various regions and provides two separate formulas for heavy and light oils. 
Recommended applicability range:

• Oil density (API Gravity): 10 – 48 °API
• Temperature: 60 – 300 °F
• Viscosity: 1 – 50,000 cP

Petrosky

The Petrosky (1990) correlation was developed based on the analysis of PVT properties of crude oils from Gulf of Mexico fields. A key feature of the model is its adaptation to high-temperature conditions and oils with elevated gas content, which are typical for the region. The correlation performs well for paraffinic oils. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Temperature: 80 – 320 °F
• Viscosity: 0.5 – 200 cP

Egbogah

The Egbogah correlation was specifically developed for accurate prediction of dead oil viscosity, especially under high-temperature conditions and for heavy fluids. Unlike classical methods (Beal, Beggs & Robinson), this correlation incorporates an enhanced temperature dependence and modified coefficients, providing better accuracy for oils with API < 25°. The formula is based on statistical analysis of data from Canadian oil fields, making it particularly useful for oils with atypical properties. 
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Temperature: 50 – 300 °F
• Viscosity: 1 – 100,000 cP

Kartohadiprodjo & Schmidt

This correlation was developed based on an extensive database comprising over 4,500 crude oil samples from around the world. It is considered one of the most universal and accurate methods for estimating dead oil viscosity, especially across a wide range of oil densities. Additionally, it accounts for the nonlinear dependence of viscosity on both temperature and oil gravity. It is claimed to outperform Beggs & Robinson and Glaso correlations in terms of accuracy, particularly for heavy oils. 
Recommended applicability range:

• Oil density (API Gravity): 6 – 50 °API
• Temperature: 70 – 295 °F
• Viscosity: 1 – 10,000 cP (highest accuracy in the range of 10 – 1,000 cP)

Khan

The Khan correlation is a modified version of the classical Beggs & Robinson method, specifically developed for accurate prediction of dead oil viscosity across a wide range of temperatures and oil gravities. The method introduces additional correction factors that enhance accuracy for heavy oils and high-temperature conditions. The formula is based on statistical analysis of data from Pakistani oil fields but has demonstrated good applicability to other regions. 
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Temperature: 70 – 300 °F
• Viscosity: 1 – 10,000 cP (highest accuracy in the range of 10 – 1,000 cP)

Glaso

The Glaso correlation was developed based on PVT data analysis for North Sea crude oils. It estimates dead oil viscosity at atmospheric pressure using oil density and temperature. Compared to the Beal and other early correlations, Glaso offers a wider temperature applicability range. It is particularly suitable for North Sea oils but has been validated on fields in other regions as well. 
Recommended applicability range:

• Oil density (API Gravity): 15 – 50 °API
• Temperature: 50 – 300 °F
• Viscosity: 0.5 – 50 cP