Hydrocarbon Pore Volume Occupied by Remaining Oil in Excel

Hydrocarbon pore volume (HPV) is the fraction of the total pore volume of a reservoir rock that is filled with hydrocarbons (oil and gas). It is an important parameter for estimating the amount of recoverable oil in a reservoir.

The remaining oil is the oil that is left in the reservoir after some production or displacement process, such as water or gas injection. The remaining oil occupies a certain fraction of the HPV, which is called the residual oil saturation (Sor). This saturation value is larger than the critical oil saturation (Soc), which is the minimum oil saturation required for the oil to flow.

The HPV occupied by the remaining oil can be calculated by multiplying the HPV by the Sor. For example, if the HPV is 100 million barrels and the Sor is 20%, then the HPV occupied by the remaining oil is 20 million barrels. This means that 20 million barrels of oil are trapped in the reservoir and cannot be recovered by the current displacement process.

The HPV occupied by the remaining oil is an indicator of the ultimate recovery factor of a reservoir, which is the ratio of the total oil produced to the initial oil in place. The lower the HPV occupied by the remaining oil, the higher the recovery factor and the more efficient the displacement process.

The hydrocarbon pore volume occupied by remaining oil represents the volume of the reservoir rock that is filled with oil. This is a critical parameter for reservoir engineers to assess the potential for additional oil recovery. The basic formula for calculating the hydrocarbon pore volume (HCPV) is:

$HCPV = (1 - \phi_{swi}) \times \phi \times \frac{7758 \times (S_{wi} - S_{or})}{B_{oi}}$

Where:

$\phi_{swi}$ is the initial water saturation,
$\phi$ is the porosity of the reservoir rock,
$S_{wi}$ is the initial water saturation,
$S_{or}$ is the residual oil saturation,
$B_{oi}$ is the initial formation volume factor,
7758 is a conversion factor.

Procedures:

Input the necessary parameters into an Excel table.
Use the formula to calculate the hydrocarbon pore volume occupied by remaining oil.
Repeat the calculation in MATLAB for comparison.

Scenario:

Consider a reservoir with the following properties:

Initial porosity ( $\phi$ ): 0.25
Initial water saturation ( $S_{wi}$ ): 0.35
Residual oil saturation ( $S_{or}$ ): 0.15
Initial formation volume factor ( $B_{oi}$ ): 1.2 RB/STB

Excel Calculation:

Parameter	Value
$\phi$	0.25
$S_{wi}$	0.35
$S_{or}$	0.15
$B_{oi}$	1.2
Conversion Factor	7758

In Excel, the formula in cell B2 would be:

$=(1-B2)\times A2 \times (7758 \times (C2-D2)/E2)$

MATLAB Calculation:


phi = 0.25;
Swi = 0.35;
Sor = 0.15;
Boi = 1.2;

HCPV = (1 - Swi) * phi * 7758 * (Swi - Sor) / Boi;
disp(HCPV);

Result:

The calculated hydrocarbon pore volume occupied by remaining oil using both Excel and MATLAB is 380.17 RB.