Determining Hydrocarbon Pore Volume Occupied by Evolved Solution Gas in Petroleum Engineering using Excel

Hydrocarbon pore volume is the amount of space in a reservoir that is filled with oil and gas. Evolved solution gas is the gas that comes out of the oil when the pressure drops below a certain point. The gas that comes out of the oil occupies some of the pore space, reducing the amount of space available for the oil.

The pore volume occupied by the evolved solution gas can be calculated by using the material balance equation, which is a way of keeping track of the mass and volume of fluids in the reservoir.

Basic Theory:

The hydrocarbon pore volume occupied by evolved solution gas is calculated using the equation:

    \[ \text{Hydrocarbon Pore Volume} = \frac{\text{Evolved Solution Gas Volume}}{\text{Gas-Oil Ratio (GOR)}} \]

Where:

  • Evolved Solution Gas Volume is the volume of gas liberated from the hydrocarbons due to pressure depletion.
  • Gas-Oil Ratio (GOR) is the ratio of produced gas volume to produced oil volume.

Procedures:

  1. Data Collection: Gather data on reservoir pressure, initial gas-oil ratio, and initial reservoir conditions.
  2. Calculate Evolved Solution Gas Volume: Use the material balance equation to determine the evolved solution gas volume.
  3. Determine Gas-Oil Ratio (GOR): Calculate the Gas-Oil Ratio (GOR) using the produced gas volume and produced oil volume.
  4. Calculate Hydrocarbon Pore Volume: Apply the formula mentioned above to find the hydrocarbon pore volume occupied by evolved solution gas.

Example:

Consider a reservoir with the following parameters:

  • Initial reservoir pressure = 3,000 psi
  • Initial gas-oil ratio (GOR) = 500 scf/STB
  • Produced gas volume = 10,000 scf
  • Produced oil volume = 100 STB

Calculation in Excel:

Parameter Value
Initial Reservoir Pressure (psi) 3,000
Initial GOR (scf/STB) 500
Produced Gas Volume (scf) 10,000
Produced Oil Volume (STB) 100

    \[ \text{Evolved Solution Gas Volume} = \text{Initial GOR} \times \text{Produced Oil Volume} \]

    \[ \text{Hydrocarbon Pore Volume} = \frac{\text{Evolved Solution Gas Volume}}{\text{Produced Gas Volume}} \]

Result in Excel:

    \[ \text{Hydrocarbon Pore Volume} = \frac{(500 \times 100)}{10,000} = 5 \ \text{STB} \]

Calculation in MATLAB:

% MATLAB code for calculating Hydrocarbon Pore Volume
initialGOR = 500;
producedOilVolume = 100;
producedGasVolume = 10000;

evolvedSolutionGasVolume = initialGOR * producedOilVolume;
hydrocarbonPoreVolume = evolvedSolutionGasVolume / producedGasVolume;

disp(['Hydrocarbon Pore Volume: ', num2str(hydrocarbonPoreVolume), ' STB']);

Result in MATLAB:

    \[ \text{Hydrocarbon Pore Volume} = 5 \ \text{STB} \]

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