Oil saturation is calculated by dividing the total volume of oil present in a grid by the macro pore volume of that grid. This measurement specifically considers the oil saturation located within the effective porosity of the rock.
Understanding Oil Saturation
Oil saturation is a critical parameter in reservoir engineering, representing the fraction of the pore space within a rock formation that is occupied by oil. It is crucial for estimating the amount of oil that can be recovered from a reservoir. Here's a breakdown of the concept:
What is Effective Porosity?
- Porosity is the measure of the void space in a rock.
- Effective porosity refers to the interconnected pore space that contributes to fluid flow. This excludes isolated pores that don't allow for the movement of oil or other fluids.
Macro Pore Volume
The macro pore volume refers to the volume of the larger, connected pore spaces within a rock formation. These are the spaces where oil tends to accumulate and move.
The Calculation Process
The calculation of oil saturation, specifically within the effective porosity, involves:
-
Determining the Total Volume of Oil: This is the aggregate volume of oil present within the designated grid or area being studied.
-
Determining the Macro Pore Volume: This is the total volume of connected pore spaces within that same grid.
-
Dividing Oil Volume by Macro Pore Volume: The oil saturation (So) is then calculated using the formula:
So = Total Volume of Oil / Macro Pore Volume- Where:
- So = Oil Saturation
- Where:
Why is this important?
- Volumetric Calculations: The oil saturation in the effective porosity is used in reservoir calculations to estimate the original oil in place (OOIP) and the recoverable oil.
- Reservoir Characterization: It helps understand the reservoir's fluid distribution and its potential for production.
- Production Strategy: Knowing the oil saturation assists in designing effective extraction and recovery methods.
Example
Let's assume a grid has:
| Parameter | Value |
|---|---|
| Total Volume of Oil | 500 m³ |
| Macro Pore Volume | 1000 m³ |
Then, the oil saturation would be:
So = 500 m³ / 1000 m³ = 0.5
This means 50% of the macro pore volume within the effective porosity is occupied by oil.
In Summary
Oil saturation, specifically calculated within the effective porosity, is a crucial factor for reservoir evaluation and planning. The process involves dividing the total oil volume by the macro pore volume of the grid. This data is used in volumetric calculations to determine the amount of oil in place and to inform reservoir management decisions.
