ASTM D6377 - Reid Vapor Pressure

ASTM D6377 provides methods for determining vapor pressure of crude oil and petroleum products.

Table of Contents

Overview

Standard: ASTM D6377 - Standard Test Method for Determination of Vapor Pressure of Crude Oil: VPCRx (Expansion Method)

Purpose: Determine the vapor pressure of crude oil and condensates for:

Class: Standard_ASTM_D6377

Vapor Pressure Definitions

True Vapor Pressure (TVP)

The equilibrium pressure of vapor above a liquid at a specified temperature when vapor/liquid ratio approaches zero.

\[TVP = P_{bubble}(T)\]

Reid Vapor Pressure (RVP)

The vapor pressure measured at 100°F (37.8°C) in a standardized apparatus with vapor/liquid volume ratio of 4:1.

VPCR4 (Vapor Pressure at V/L = 4)

The pressure at which 80% by volume is vapor at 37.8°C (100°F).

VPCR Relationship

Different VPCR ratios are used in various standards:

Implementation

Constructor

import neqsim.standards.oilquality.Standard_ASTM_D6377;

// Create standard from fluid
Standard_ASTM_D6377 rvpStandard = new Standard_ASTM_D6377(thermoSystem);

Available Methods

Method Name Description
VPCR4 Vapor pressure at V/L = 4 (default)
VPCR4_no_water VPCR4 excluding water
RVP_ASTM_D6377 RVP correlation from D6377
RVP_ASTM_D323_73_79 RVP per D323 (1973/1979)
RVP_ASTM_D323_82 RVP per D323 (1982)

Key Methods

Method Description
calculate() Perform vapor pressure calculations
getValue("RVP", "bara") Get Reid vapor pressure
getValue("TVP", "bara") Get true vapor pressure
getValue("VPCR4", "bara") Get VPCR4
setMethodRVP(method) Select RVP calculation method
getMethodRVP() Get current method

Usage Examples

Basic RVP Calculation

import neqsim.thermo.system.SystemSrkEos;
import neqsim.standards.oilquality.Standard_ASTM_D6377;

// Create condensate/crude composition
SystemInterface crude = new SystemSrkEos(273.15 + 15, 1.01325);
crude.addComponent("methane", 0.01);
crude.addComponent("ethane", 0.02);
crude.addComponent("propane", 0.04);
crude.addComponent("n-butane", 0.06);
crude.addComponent("i-butane", 0.03);
crude.addComponent("n-pentane", 0.08);
crude.addComponent("i-pentane", 0.05);
crude.addComponent("n-hexane", 0.10);
crude.addTBPfraction("C7", 0.15, 100.0/1000.0, 0.72);
crude.addTBPfraction("C10", 0.20, 142.0/1000.0, 0.78);
crude.addTBPfraction("C20", 0.26, 282.0/1000.0, 0.85);
crude.setMixingRule("classic");

// Calculate RVP
Standard_ASTM_D6377 rvpStandard = new Standard_ASTM_D6377(crude);
rvpStandard.setMethodRVP("VPCR4");
rvpStandard.calculate();

// Get results
double tvp = rvpStandard.getValue("TVP", "bara");
double rvp = rvpStandard.getValue("RVP", "bara");
double vpcr4 = rvpStandard.getValue("VPCR4", "bara");

System.out.println("=== Vapor Pressure Results ===");
System.out.printf("True Vapor Pressure (TVP) = %.4f bara%n", tvp);
System.out.printf("Reid Vapor Pressure (RVP) = %.4f bara%n", rvp);
System.out.printf("VPCR4 = %.4f bara%n", vpcr4);

Comparing Different RVP Methods

// Calculate using all available methods
String[] methods = {"VPCR4", "RVP_ASTM_D6377", "RVP_ASTM_D323_73_79", "RVP_ASTM_D323_82"};

System.out.println("Method                | RVP (bara)");
System.out.println("----------------------|----------");

for (String method : methods) {
    Standard_ASTM_D6377 std = new Standard_ASTM_D6377(crude);
    std.setMethodRVP(method);
    std.calculate();
    double rvp = std.getValue("RVP", "bara");
    System.out.printf("%-21s | %.4f%n", method, rvp);
}

Effect of Light Ends on RVP

// Analyze RVP sensitivity to light ends
double[] methaneContent = {0.0, 0.005, 0.01, 0.02, 0.05};

System.out.println("Methane (mol%) | RVP (bara)");
System.out.println("---------------|----------");

for (double ch4 : methaneContent) {
    SystemInterface fluid = new SystemSrkEos(273.15 + 15, 1.0);
    fluid.addComponent("methane", ch4);
    fluid.addComponent("ethane", 0.02);
    fluid.addComponent("propane", 0.04);
    fluid.addComponent("n-butane", 0.08);
    fluid.addComponent("n-pentane", 0.10);
    fluid.addTBPfraction("C7", 0.20, 100/1000.0, 0.72);
    fluid.addTBPfraction("C15", 0.56 - ch4, 200/1000.0, 0.80);
    fluid.setMixingRule("classic");
    
    Standard_ASTM_D6377 std = new Standard_ASTM_D6377(fluid);
    std.calculate();
    double rvp = std.getValue("RVP", "bara");
    
    System.out.printf("%14.1f | %.4f%n", ch4 * 100, rvp);
}

Wet vs Dry RVP

// Calculate with and without water
SystemInterface wetCrude = crude.clone();
wetCrude.addComponent("water", 0.01);  // 1% water

Standard_ASTM_D6377 wetStd = new Standard_ASTM_D6377(wetCrude);
wetStd.calculate();

double vpcr4Wet = wetStd.getValue("VPCR4", "bara");
double vpcr4Dry = wetStd.getValue("VPCR4_no_water", "bara");

System.out.printf("VPCR4 (with water) = %.4f bara%n", vpcr4Wet);
System.out.printf("VPCR4 (dry basis) = %.4f bara%n", vpcr4Dry);

Method Selection

VPCR4 (Default)

Best for:

RVP_ASTM_D6377

Correlation from ASTM D6377: \(RVP = 0.834 \times VPCR4\)

RVP_ASTM_D323_82

Correlation from ASTM D323 (1982 edition): \(RVP = \frac{0.752 \times (100 \times VPCR4) + 6.07}{100}\)

RVP_ASTM_D323_73_79

For comparison with historical data using D323 (1973/1979 editions). Uses VPCR4 without water contribution.

Correlations

TVP to RVP

Approximate relationship: \(RVP \approx 0.75 \times TVP + constant\)

The constant depends on crude composition.

Temperature Dependence

For estimation at temperatures other than 37.8°C:

\[\log_{10}(P_{vap}) = A - \frac{B}{T + C}\]

Antoine-type equation where A, B, C are crude-specific.

RVP Specifications

Product Typical RVP Limit
Crude oil (export) < 0.7 bara (10 psia)
Stabilized condensate < 0.5 bara (7 psia)
Gasoline (summer) < 0.62 bara (9 psi)
Gasoline (winter) < 0.90 bara (13 psi)

Technical Details

Calculation Procedure

  1. Set temperature to 37.8°C (100°F)
  2. Perform bubble point flash to get TVP
  3. Perform flash at vapor/liquid volume ratio = 4
  4. Apply correlation for RVP estimation

Reference Conditions

Parameter Value
Temperature 37.8°C (100°F)
V/L ratio 4:1 (80% vapor by volume)
Pressure Equilibrium

Equation of State

Uses SRK-EoS for phase equilibrium calculations.

Accuracy Considerations

Factors Affecting Accuracy

  1. Light end characterization - Accurate C1-C4 composition critical
  2. Heavy end representation - TBP fractions affect liquid volume
  3. Water content - Can significantly affect measured RVP
  4. Sample handling - Light end loss during sampling

Typical Uncertainty

Method Uncertainty
VPCR4 calculation ±0.02 bara
RVP correlation ±0.03-0.05 bara

Recommendations

  1. Ensure accurate light ends (C1-C5) analysis
  2. Use consistent method for comparison
  3. Report method used with results
  4. Consider water content effects

References

  1. ASTM D6377 - Standard Test Method for Determination of Vapor Pressure of Crude Oil: VPCRx (Expansion Method)
  2. ASTM D323 - Standard Test Method for Vapor Pressure of Petroleum Products (Reid Method)
  3. ASTM D5191 - Standard Test Method for Vapor Pressure of Petroleum Products and Liquid Fuels (Mini Method)
  4. API MPMS Chapter 8 - Sampling