Ineffective Porosity
Ineffective porosity, a dimensionless number, is the portion of the porosity within a reservoir rock that does not contribute to the storage and flow of fluids, such as oil, gas, or water. The following types of porosity do not contribute to the effective porosity, which is the porosity that actually contributes to the reservoir's ability to store and transmit fluids. Understanding the distinction between effective and ineffective porosity is crucial for accurate reservoir characterization and for making informed decisions regarding reservoir management and production strategies.
Ineffective porosity includes
- Isolated Pores - Pores that are not connected to the pore network and therefore cannot contribute to fluid flow.
- Clay-bound Water - Water that is tightly bound to clay minerals within the rock and is not movable under normal reservoir conditions.
- Microporosity - Very small pores where the capillary forces prevent the flow of hydrocarbons.
- Dead-end Pores - Pores that are connected to the pore network but do not contribute to fluid flow because they do not have an outlet.
Ineffective Porosity formula
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\( n_i \;=\; V_{dp} \;/\; V_b \) (Ineffective Porosity) \( V_{dp} \;=\; n_i \; V_b \) \( V_b \;=\; V_{dp} \;/\; n_i \) |
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| Symbol | English | Metric |
| \( n_i \) = Ineffective Porosity | \(dimensionless\) | \(dimensionless\) |
| \( V_{dp} \) = Volume of Completely Disconnected Pores | \(in^3\) | \(cm^3\) |
| \( V_b \) = Bulk Volume | \(in^3\) | \(cm^3\) |
