Appendix A: PVT Correlations

1. OIL

Bubble Point Pressure and Gas Solubility

Al-Marhoun

The Al-Marhoun correlation (1988) was developed to calculate the bubble point pressure of crude oil based on data from Middle Eastern oilfields. It takes into account temperature, gas-oil ratio, gas density, and oil density. It was specifically designed for Middle Eastern crude oils. The correlation provides good accuracy for high-sulfur oils and serves as an alternative to the Standing and Vasquez & Beggs correlations for certain regions.
Recommended applicability range:

• Oil density (API Gravity): 20 – 55 °API
• Gas-oil ratio: 25 – 1600 SCF/STB
• Temperature: 75 – 240 °F
• Pressure: 130 – 3500 psi

De Ghetto et al.

The De Ghetto et al. correlation (1995) provides several specialized formulas for calculating bubble point pressure based on oil density. The method is derived from data from Mediterranean and Venezuelan oilfields. The correlation offers high accuracy for heavy and medium crudes, where traditional correlations (Standing, Vasquez & Beggs) often produce significant errors. For extra-heavy oils (<10 °API), it is the only correlation that delivers acceptable accuracy.
Recommended applicability range:

• Oil density (API Gravity): 5 – 40 °API
• Gas-oil ratio: 20 – 1500 SCF/STB
• Temperature: 100 – 280 °F

Glaso

The Glaso correlation was developed based on an extensive database of crude oils from the North Sea and other regions. It accounts for the influence of gas-oil ratio, temperature, oil density, and gas specific gravity, making it applicable to various types of fluids. The method uses logarithmic transformations and polynomial relationships, providing high accuracy, especially for light and medium oils. Unlike earlier correlations (e.g., Standing), the Glaso correlation performs better for oils containing dissolved gas over a wide pressure range.
Recommended applicability range:

• Oil density (API Gravity): 22 – 48 °API
• Gas-oil ratio: 90 – 2500 SCF/STB
• Temperature: 80 – 280 °F
• Pressure: 100 – 5000 psi

Lasater

The Lasater correlation is one of the earliest reliable methods for calculating the bubble point pressure of crude oil. The calculation is based on the mole fraction of dissolved gas. It shows particular accuracy for medium and heavy oils (< 40 °API). The method uses empirical relationships derived from the analysis of oils from Canada and the United States.
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Gas-oil ratio: 50 – 3500 SCF/STB
• Temperature: 100 – 300 °F
• Pressure: 100 – 5000 psi

Petrosky

The Petrosky correlation was developed for crude oils from the Gulf of Mexico. It demonstrates improved accuracy for this region compared to traditional methods. The correlation accounts for the thermodynamic properties of offshore shelf crudes and serves as an alternative to the Standing and Vasquez & Beggs correlations for offshore fields. The average error is ±6.5% compared to laboratory data.
Recommended applicability range:

• Oil density (API Gravity): 16 – 45 °API
• Gas-oil ratio: 200 – 1500 SCF/STB
• Temperature: 110 – 300 °F
• Pressure: 1500 – 4000 psi

Standing

The Standing correlation is used to calculate the bubble point pressure of crude oil based on the gas-oil ratio, gas specific gravity, oil gravity, and temperature. Originally developed for California crude oils, it has since been widely applied to other regions. The correlation is known for its simplicity, minimal input requirements, and good accuracy for light oils (25–40 °API). However, it tends to overestimate results for heavy oils (<20 °API).
Recommended applicability range:

• Oil density (API Gravity): 16 – 45 °API
• Gas-oil ratio: 20 – 1500 SCF/STB
• Temperature: 100 – 300 °F

Vasquez & Beggs

The Vasquez & Beggs correlation improves the calculation of bubble point pressure by: normalizing gas specific gravity to a reference pressure of 100 psi; dividing oils into three groups based on API gravity; and accounting for temperature and gas-oil ratio. It was developed using a global database of 600 PVT analyses. The correlation also considers separation conditions. It is less accurate for heavy oils (<20 °API).
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Gas-oil ratio: 20 – 2070 SCF/STB
• Temperature: 75 – 295 °F

Kartoatmodjo & Schmidt

The Kartoatmodjo & Schmidt correlation provides two separate formulas: one for oils with API ≤ 30 and another for API > 30, allowing for higher accuracy across different fluid types. The method accounts for the influence of gas-oil ratio, temperature, oil gravity, and separator gas properties. A key feature is the use of a correction factor to account for gas separation conditions. It is particularly effective for Southeast Asian crudes and other regions with similar characteristics.
Recommended applicability range:

• Oil density (API Gravity): 14 – 45 °API
• Gas-oil ratio: 20 – 2500 SCF/STB
• Temperature: 100 – 300 °F

Saturated Oil Formation Volume Factor

Al-Marhoun

The Al-Marhoun correlation (1988) was specifically developed for Middle Eastern crude oils based on an extensive PVT database. The method takes into account the effects of gas-oil ratio, oil and gas specific gravity, and temperature, offering improved accuracy compared to classical correlations such as Standing and Glaso. A key feature is the use of a power-law relationship optimized for Middle Eastern reservoir conditions. The formula is not applicable to oils with abnormal composition (e.g., high content of harmful components).
Recommended applicability range:

• Oil density (API Gravity): 20 – 45 °API
• Gas-oil ratio: 100 – 2500 SCF/STB
• Gas specific gravity: 0.65 – 1.2
• Temperature: 100 – 300 °F

De Ghetto et al.

The De Ghetto et al. correlation represents an advanced method for calculating the formation volume factor of saturated oil, specifically designed for use with heavy and highly viscous oils (API < 25°). Unlike classical methods (e.g., Standing, Vasquez & Beggs), this correlation applies separate calculation approaches for light and heavy fluids, resulting in improved prediction accuracy. The formula incorporates the combined effects of gas-oil ratio, temperature, oil and gas densities through a system of power-law relationships.
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Gas-oil ratio: 50 – 3000 SCF/STB
• Temperature: 100 – 300 °F

Glaso

The Glaso correlation allows calculation of the formation volume factor of saturated oil based on the gas-oil ratio, gas and oil density, and temperature. It was developed for North Sea crude oils but is also applicable to other regions. The method is known for its high accuracy with light and medium oils but tends to be less precise for heavy fluids.

Recommended applicability range:

• Oil density (API Gravity): 22 – 48 °API
• Gas-oil ratio: 90 – 2500 SCF/STB
• Temperature: 80 – 280 °F

Lasater

The Lasater correlation (1958) is based on the analysis of North American crude oils with a focus on the effect of gas solubility. The method uses the mole fraction of gas in the system for calculation, which makes it particularly accurate for gas-saturated oils. The approach is physically based but requires knowledge of the oil’s molecular weight. It tends to overestimate values for heavy oils. It does not account for sulfur or paraffin content.
Recommended applicability range:

• Oil density (API Gravity): 15 – 40 °API
• Gas-oil ratio: 50 – 3500 SCF/STB
• Temperature: 100 – 220 °F

Petrosky

The Petrosky correlation is used to estimate the formation volume factor of saturated oil based on reservoir oil parameters such as gas-oil ratio, gas and oil density, and temperature. It was developed for crude oils from the Gulf of Mexico, but the correlation also shows good accuracy for similar reservoirs. The formula takes into account the influence of dissolved gas.
Recommended applicability range:

• Oil density (API Gravity): 15 – 40 °API
• Gas-oil ratio: 90 – 3000 SCF/STB
• Pressure: up to 7000 psi
• Temperature: 120 – 300 °F

Standing

The Standing correlation is one of the most widely used empirical models for estimating the formation volume factor of saturated oil. It is based on data from California oilfields and takes into account the gas-oil ratio, specific gravity of oil and gas, and reservoir temperature. Simple to apply, this correlation delivers acceptable accuracy for "black oil" models.
Recommended applicability range:

• Oil density (API Gravity): 22 – 58 °API
• Gas-oil ratio: 20 – 2100 SCF/STB
• Pressure: up to 5000 psi
• Temperature: 100 – 260 °F

Vasquez & Beggs

The Vasquez & Beggs correlation is one of the most versatile and widely used models for calculating the formation volume factor of saturated oil. It was developed based on an extensive database of over 600 oil samples. The formula categorizes oils into several groups based on API gravity. A distinguishing feature of the correlation is the normalization of gas parameters to standard separation conditions, which enhances its accuracy.
Recommended applicability range:

• Oil density (API Gravity): 15 – 55 °API
• Gas-oil ratio: 0 – 3000 SCF/STB
• Gas specific gravity (air = 1): 0.58 – 1.18
• Temperature: 70 – 295 °F

Ahmed

The Ahmed correlation was developed as a modification of existing models to provide more accurate predictions of the saturated oil formation volume factor. It performs particularly well for heavy oils and considers the relationship between gas-oil ratio, fluid properties, and reservoir conditions. The model demonstrates good accuracy for Middle Eastern fields and yields reliable results for both heavy and medium crude oils.
Recommended applicability range:

• Oil density (API Gravity): 15 – 50 °API
• Gas-oil ratio: 50 – 3500 SCF/STB
• Gas specific gravity (air = 1): 0.65 – 1.2
• Temperature: 100 – 300 °F

Arps

The Arps correlation is a simplified linear formula used to estimate the formation volume factor of saturated oil. It relates the volume factor directly to the gas-oil ratio. The model is suitable for quick approximation calculations; however, it does not account for the effects of temperature, oil gravity, or gas gravity. This oversimplification limits its accuracy.
Recommended applicability range (exact boundaries are not defined; model is applicable within the “Black Oil” model):

• Oil density (API Gravity): 20 – 35 °API
• Gas-oil ratio: 100 – 1000 SCF/STB
• Gas specific gravity (air = 1): 0.65 – 1.0
• Temperature: 100 – 200 °F

Kartoatmodjo & Schmidt

The Kartoatmodjo & Schmidt correlation was developed based on an extensive database of over 740 crude oil samples. It is considered one of the most versatile models available. The correlation demonstrates good accuracy across a wide range of crude types—from light to heavy oils. A distinguishing feature of the method is its use of power-law relationships to account for the effects of temperature, gas-oil ratio, and fluid properties.
Recommended applicability range:

• Oil density (API Gravity): 14 – 59 °API
• Gas-oil ratio: 20 – 2900 SCF/STB
• Gas specific gravity (air = 1): 0.56 – 1.18
• Temperature: 75 – 320 °F

Undersaturated Oil Formation Volume Factor

Al-Marhoun

The Al-Marhoun correlation was specifically developed to calculate the oil formation volume factor above the bubble point pressure. The model is based on data from Middle Eastern oilfields. It accounts for the effects of pressure, temperature, and fluid properties through a power-law relationship. The correlation demonstrates good accuracy over a wide range of conditions but is most accurate for medium and heavy crude oils.
Recommended applicability range:

• Oil density (API Gravity): 19 – 45 °API
• Gas-oil ratio: 25 – 1600 SCF/STB
• Pressure: < 10,000 psi
• Gas specific gravity (air = 1): 0.75 – 1.35
• Temperature: 75 – 240 °F

De Ghetto et al.

The De Ghetto et al. correlation was developed to calculate the oil formation volume factor above the bubble point pressure. It is based on the analysis of data from heavy (<22.3 °API), medium (22.3–31.1 °API), and light (>31.1 °API) crude oils, making it suitable for a wide range of reservoir types. The model accounts for the effects of pressure, temperature, gas-oil ratio, and fluid properties. It is also suitable for reservoirs with abnormal oil characteristics.
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Gas-oil ratio: 15 – 1500 SCF/STB
• Pressure: < 8000 psi
• Gas specific gravity (air = 1): 0.65 – 1.3
• Temperature: 120 – 320 °F

A1.3.3. Glaso

The Glaso correlation is considered one of the most reliable models for calculating the oil formation volume factor in the undersaturated zone. It was developed based on North Sea crude oils. The model incorporates the effects of pressure, temperature, and fluid properties through logarithmic relationships. A key feature of the method is its high accuracy across a wide range of crude oils—from light to heavy. However, it is less accurate for oils with extreme properties (very light or very heavy).
Recommended applicability range:

• Oil density (API Gravity): 22 – 48 °API
• Gas-oil ratio: 90 – 2600 SCF/STB
• Pressure: < 8000 psi
• Gas specific gravity (air = 1): 0.65 – 1.27
• Temperature: 80 – 280 °F

Petrosky

The Petrosky correlation was specifically developed for crude oils from the Gulf of Mexico. It provides high accuracy in calculating the oil formation volume factor in the undersaturated zone. The model incorporates the effects of pressure, temperature, and fluid properties using power-law relationships. A distinctive feature of the method is its adaptability to different oil types within the defined limits. The average error is ±3–5% within the recommended applicability range. It performs especially well for reservoirs with high gas-oil ratios.
Recommended applicability range:

• Oil density (API Gravity): 16 – 45 °API
• Gas-oil ratio: 90 – 3000 SCF/STB
• Pressure: < 10,000 psi
• Gas specific gravity (air = 1): 0.6 – 0.9
• Temperature: 120 – 300 °F

Standing

The Standing correlation is a classical method for calculating the oil formation volume factor in the undersaturated zone. It was developed based on data from California oilfields and is widely used in the petroleum industry due to its simplicity and reliability. The model accounts for oil compressibility through an exponential dependence on pressure. The average error is ±5–8% within the recommended applicability range.
Recommended applicability range:

• Oil density (API Gravity): 22 – 58 °API
• Gas-oil ratio: 20 – 2100 SCF/STB
• Pressure: < 5000 psi
• Gas specific gravity (air = 1): 0.63 – 1.05
• Temperature: 100 – 250 °F

Vasquez & Beggs

The Vasquez & Beggs correlation is one of the most versatile and accurate models for calculating the oil formation volume factor in the undersaturated zone. It was developed using an extensive database of more than 600 crude oil samples. The correlation accounts for separation conditions and categorizes oils into several groups based on density, which enables high accuracy across different reservoir types.
Recommended applicability range:

• Oil density (API Gravity): 15 – 55 °API
• Gas-oil ratio: 0 – 3000 SCF/STB
• Pressure: < 10,000 psi
• Gas specific gravity (air = 1): 0.56 – 1.18
• Temperature: 70 – 295 °F

Lasater

The Lasater correlation offers an alternative approach for calculating the oil formation volume factor in the undersaturated zone, based on the mole fraction of dissolved gas. It was developed using data from Canadian and U.S. oilfields. The model performs particularly well for oils with high gas-oil ratios. However, the correlation is less accurate for heavy oils (<25 °API).
Recommended applicability range:

• Oil density (API Gravity): 20 – 48 °API
• Gas-oil ratio: 100 – 3500 SCF/STB
• Pressure: < 5000 psi
• Gas specific gravity (air = 1): 0.65 – 1.2
• Temperature: 100 – 250 °F

Ahmed

The Ahmed correlation is a modern model for calculating the oil formation volume factor in the undersaturated zone. It was developed based on a wide dataset from Middle Eastern and North African oilfields. A distinctive feature of this formula is its non-traditional approach to modeling oil compressibility through a double exponential relationship, which more accurately reflects the behavior of oils with a nonlinear volume factor dependence on pressure.
Recommended applicability range:

• Oil density (API Gravity): 25 – 40 °API
• Gas-oil ratio: 50 – 2000 SCF/STB
• Pressure: < 10,000 psi
• Temperature: 100 – 250 °F

Arps

The Arps correlation is one of the earliest practical models for estimating oil volume changes in the undersaturated zone. It was developed based on empirical data from U.S. oilfields. The method uses a linear approximation of the relationship between formation volume factor and pressure, making it simple to apply but limited in accuracy under complex reservoir conditions. At elevated pressures (> 2000 psi), the error can reach up to 10%.
Recommended applicability range:

• Oil density (API Gravity): 20 – 40 °API
• Gas-oil ratio: 100 – 1500 SCF/STB
• Pressure: < 3000 psi
• Temperature: 100 – 220 °F

Kartoatmodjo & Schmidt

The Kartoatmodjo & Schmidt correlation (1994) was developed based on an expanded global database that includes crude oil samples from various regions around the world. The method provides an advanced approach for calculating formation volume factor in the undersaturated zone, accounting for the nonlinear dependence on pressure and fluid properties. A key feature is the use of a power function to more accurately describe oil volume changes.
Recommended applicability range:

• Oil density (API Gravity): 14 – 45 °API
• Gas-oil ratio: 20 – 2500 SCF/STB
• Pressure: < 8000 psi
• Temperature: 100 – 300 °F

Compressibility

Standing

The Standing correlation, developed in 1947, is one of the earliest and most widely used methods for estimating oil compressibility. Standing proposed an empirical relationship that links compressibility with pressure, temperature, gas-oil ratio, and the specific gravities of oil and gas. The method performs particularly well for conventional crude oils with moderate gas content.
Recommended applicability range:

• Oil density (API Gravity): 20 – 45 °API
• Gas-oil ratio: 50 – 800 SCF/STB
• Temperature: 100 – 220 °F

Vasquez & Beggs

The Vasquez & Beggs correlation is an enhanced method for calculating oil compressibility, developed from an extensive PVT database. Unlike earlier models (such as Standing), this correlation explicitly accounts for the effects of pressure, temperature, gas-oil ratio, and other oil properties through a set of empirical coefficients. The method provides good accuracy across a wide range of crude oils—from light to medium.
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Pressure: < 10,000 psi
• Gas-oil ratio: 50 – 3500 SCF/STB
• Temperature: 100 – 300 °F

Glaso

The Glaso (1980) correlation for oil compressibility is based on generalized data from North Sea oilfields. The method incorporates the effects of pressure, temperature, gas-oil ratio, and oil density, offering more accurate estimates compared to classical approaches (e.g., Vasquez & Beggs). A notable feature of this model is the separation of calculation formulas for different pressure ranges—above and below the bubble point.
Recommended applicability range:

• Oil density (API Gravity): 18 – 52 °API
• Pressure: 500 – 8000 psi
• Gas-oil ratio: 50 – 3000 SCF/STB
• Temperature: 100 – 300 °F

De Ghetto et al.

This correlation was developed based on a large volume of experimental PVT data for heavy and extra-heavy crude oils, as earlier models (e.g., Standing, Vasquez & Beggs) produced significant errors for oils with API gravity below 25. The key feature of the model is the classification of fluids into multiple categories based on density, with a separate compressibility formula provided for each class. Its main limitation is that it is not universal—it performs best within the scope of the original data set.
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Pressure: < 5000 psi
• Gas-oil ratio: 0 – 2000 SCF/STB
• Temperature: 80 – 260 °F

De Ghetto et al.

This correlation was developed based on a large set of experimental PVT data for heavy and extra-heavy crude oils, as previously existing models (such as Standing and Vasquez & Beggs) produced significant errors when API gravity was below 25. The key feature of the method is the classification of fluids into several categories based on oil density. Each class has its own dedicated oil compressibility correlation. The main limitation is its lack of universality—it performs best within the bounds of the original dataset.
Recommended applicability range:

• Oil density (API Gravity): 10 – 45 °API
• Pressure: < 5000 psi
• Gas-oil ratio: 0 – 2000 SCF/STB
• Temperature: 80 – 260 °F

Petrosky

The Petrosky correlation was specifically developed for crude oils from the Gulf of Mexico, but it is also applicable to other regions. Key features of the model include consideration of gas-oil ratio, gas specific gravity, oil density, and temperature. It is optimized for light and medium crude oils. Compared to the Standing correlation, it yields more accurate results under high-temperature conditions.
Recommended applicability range:

• Oil density (API Gravity): 15 – 45 °API
• Pressure: < 8000 psi
• Gas-oil ratio: 100 – 2500 SCF/STB
• Temperature: 100 – 300 °F

Al-Marhoun

The Al-Marhoun (2003) correlation was developed to provide a more accurate estimation of oil compressibility, based on a comprehensive dataset from Middle Eastern reservoirs. The method accounts for the effects of pressure, temperature, gas-oil ratio, and fluid properties, offering improved accuracy compared to classical correlations. A distinctive feature is the use of power-law relationships optimized for various thermobaric (temperature-pressure) conditions.
Recommended applicability range:

• Oil density (API Gravity): 18 – 44 °API
• Pressure: 500 – 8000 psi
• Gas-oil ratio: 50 – 3000 SCF/STB
• Temperature: 100 – 300 °F

Lasater

The Lasater (1958) correlation was developed based on the analysis of crude oils from Canadian and U.S. fields. The method uses an empirical relationship linking oil compressibility with pressure, gas-oil ratio, and fluid properties. A key feature of this approach is its emphasis on the influence of gas solubility, making it particularly useful for oils with high gas content. At pressures above 3000 psi, the correlation may underestimate compressibility—other models are recommended for such conditions.
Recommended applicability range:

• Oil density (API Gravity): 20 – 45 °API
• Pressure: 100 – 3000 psi
• Gas-oil ratio: 50 – 1500 SCF/STB
• Temperature: 100 – 250 °F

Ahmed

The empirical correlation proposed by Tarek Ahmed is used to estimate the isothermal compressibility of crude oil. It is based on the analysis of PVT data for light and medium crude oils and is applicable when laboratory measurements are not available. The model accounts for the effects of pressure, dissolved gas, temperature, and oil density. It is known for its simplicity and reliable results under typical reservoir conditions. The correlation is well-suited for early-stage design or reservoir simulators where a quick property estimation is needed.
Recommended applicability range:

• Oil density (API Gravity): 20 – 45 °API
• Pressure: < 5000 psi
• Gas-oil ratio: 0 – 2000 SCF/STB
• Temperature: 100 – 300 °F

Kartoatmodjo & Schmidt

This correlation is a modern method for calculating oil compressibility, developed using an extensive database of PVT analyses. Unlike classical approaches (e.g., Standing, Vasquez & Beggs), this method is specifically optimized for heavy and highly viscous crude oils, showing particular accuracy under challenging conditions. The formula captures the combined influence of pressure, temperature, gas-oil ratio, and oil density through a system of power-law relationships.
Recommended applicability range:

• Oil density (API Gravity): 10 – 50 °API
• Pressure: < 8000 psi
• Gas-oil ratio: 20 – 2500 SCF/STB
• Temperature: 80 – 320 °F

Heat Capacity

Wright

The Wright (1991) correlation was developed to calculate the isobaric heat capacity of crude oils over a wide range of temperatures and pressures. The method is based on generalized experimental data for various types of crude, including heavy and bituminous oils. A distinguishing feature of the model is its consideration of oil density, temperature, and pressure through polynomial relationships.
Recommended applicability range:

• Oil density (API Gravity): 10 – 50 °API
• Pressure: < 5000 psi
• Temperature: 50 – 350 °F

Oil Density

McCain

The McCain (1990) correlation is one of the most reliable methods for calculating the density of reservoir oil. It was developed using an extensive PVT database from U.S. oilfields. A key feature of this method is its consideration of the effects of dissolved gas, pressure, and temperature on oil density. The correlation is widely used in engineering calculations due to its strong accuracy and physical relevance.
Recommended applicability range:

• Temperature: 100 – 300 °F
• Oil density (API Gravity): 18 – 45 °API
• Gas-oil ratio: 50 – 3000 SCF/STB
• Pressure: 500 – 10,000 psi

Ahmed

This correlation was developed by Tarek Ahmed and published in his classic work Reservoir Engineering Handbook (1989). It is intended for estimating the density of gas-saturated crude oil under standard conditions. The correlation is widely used in PVT analysis when laboratory data is unavailable. It expresses oil density as a function of gas-oil ratio, oil specific gravity, and gas specific gravity.
Recommended applicability range:

• Oil density (API Gravity): 10 – 50 °API
• Gas-oil ratio: 0 – 2000 SCF/STB
• Gas specific gravity (air = 1): 0.6 – 1.3

Katz

The Katz (1942) correlation is one of the earliest and most well-known empirical models for estimating reservoir oil density, accounting for the effect of dissolved gas. It is based on extensive experimental data. This correlation was widely used before the development of more advanced models such as Standing and Vasquez & Beggs.
Recommended applicability range:

1. Temperature: 60 – 220 °F
2. Oil density (API Gravity): 15 – 45 °API
3. Gas-oil ratio: 20 – 1000 SCF/STB
4. Pressure: 100 – 5000 psi

Standing

The Standing (1947) correlation is a classical method for calculating oil density under reservoir conditions. It accounts for the effects of dissolved gas, pressure, temperature, and the properties of both oil and gas. Based on experimental data from California oilfields, the correlation remains widely used today in black oil models.
Recommended applicability range:

• Temperature: 60 – 250 °F
• Oil density (API Gravity): 15 – 45 °API
• Gas-oil ratio: 20 – 1500 SCF/STB
• Pressure: 50 – 5000 psi

1. WATER

2. A2.1. Formation Volume Factor

McCain

The McCain (1990) correlation is a classical method for calculating the formation water volume factor. The method accounts for the effects of pressure, temperature, salinity (TDS), and dissolved gas, offering a physically grounded model with high accuracy. A key feature is the separate treatment of water compressibility and thermal expansion. For formation waters with TDS > 50,000 ppm, a salinity correction is required.
Recommended applicability range:

• Temperature: 100 – 400 °F
• Salinity (TDS): 0 – 200,000 ppm
• Gas content: 0 – 50 SCF/STB
• Pressure: 14.7 – 10,000 psi

1. A2.2. Viscosity

McCain

The McCain (1991) correlation estimates the viscosity of formation water based on temperature, pressure, and salinity. It accounts for the effect of dissolved salts, making it more accurate than simple correlations for pure water. The model is based on experimental data and is widely used in the oil and gas industry. It provides good accuracy for moderately to highly saline waters, but for highly mineralized water (near the applicability limits), comparison with laboratory data is recommended.
Recommended applicability range:

• Salinity: up to 200,000 ppm
• Temperature: 30 – 300 °F
• Pressure: < 10,000 psi

Beggs & Brill

The Beggs & Brill (1973) correlation was developed to calculate water viscosity in oil production processes. It is especially applicable to multiphase flow in wells. The formula accounts for the effects of temperature and pressure but does not include a correction for salinity, making it more suitable for relatively fresh formation waters.
Recommended applicability range:

• Salinity: not considered; suitable for low-salinity water
• Temperature: 60 – 300 °F
• Pressure: < 10,000 psi

Matthews & Russell

The Matthews & Russell (1967) correlation allows for estimating the viscosity of formation water by considering temperature, pressure, and salinity. It is based on experimental data and is suitable for engineering calculations in the oil and gas industry. Unlike McCain's method, this correlation uses a simpler model but remains popular due to its reliability under standard conditions.
Recommended applicability range:

• Salinity: up to 200,000 ppm
• Temperature: 60 – 400 °F
• Pressure: < 10,000 psi

HP Petroleum

HP Petroleum is a modern commercial software package for modeling PVT properties, incorporating advanced correlations for calculating water viscosity. Unlike classical correlations, HPPFP uses more sophisticated models that account for:

• Temperature effects (from cryogenic to high-temperature conditions),
• Pressure (including ultra-high pressures),
• Salinity (including complex salt compositions),
• Dissolved gases (H₂S, CO₂).

Recommended applicability range:

• Temperature: 30 – 500 °F
• Salinity: up to 300,000 ppm
• Pressure: < 10,000 psi

1. A2.3. Oil Viscosity

A2.3.1. 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)