# How do you find the porosity of a well log?

**logs**: also called neutron

**logs**, determine

**porosity**by assuming that the reservoir pore spaces are filled with either water or oil and then measuring the amount of hydrogen atoms (neutrons) in the pores. These

**logs**underestimate the

**porosity**of rocks that contain gas.

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Beside this, how do you calculate the effective porosity of a log?

Total **porosity** minus clay-bound water (CBW). **Log effective porosity**. In essence, total **porosity** minus shale water, where solid minerals and the volume of shale (Vsh) constitute the matrix (non-**effective porosity**) and the remaining volume constitutes the **effective porosity**.

Similarly, what is porosity log? Neutron **logs** are **porosity logs** that measure the hydrogen ion concentration in a formation. In clean formations (i.e. shale-free) where the **porosity** is filled with water or oil, the neutron **log** measures liquid-filled **porosity**. Neutrons are created from a chemical source in the neutron **logging** tool.

Keeping this in view, how do you find the porosity of a density log?

**Obtaining porosities from a density log**

- Φ = porosity.
- ρ
_{ma}= matrix density (see table below) - ρ
_{b}= formation bulk density (log value) - ρ
_{f}= density of the fluid saturating the rock immediately surrounding the borehole—usually mud filtrate (use 1.0 for freshwater and 1.1 for saltwater mud)

How do you determine porosity?

There are two basic equations used to **calculate porosity**. The first equation uses the total volume and the volume of the void. **Porosity** = (Volume of Voids / Total Volume) x 100%. The second equation uses the total volume and the volume of the solid.