Do you know that rocks aren’t completely solid? All rocks contain tiny spaces between its grains called pores. Porosity is described as a measure of the capacity of reservoir rocks to store fluids. ^[1] High porosity is valued because it means a reservoir can hold much oil.

Factors influencing porosity^[2]:

1. The arrangement of the grains, also known as granular packing. A tidy arrangement will yield higher porosity.

• The sorting of the grains. A well-sorted sandstone has grains with similar sizes and tends to have greater porosity.^[3]
• Ineffective porosity. Chemical reactions may cause grains to cement together and isolate the fluid inside them. In the oil field, we are only concerned with the effective porosity.

Source:

1. Ezekwe, N. (2010). Petroleum Reservoir Engineering Practice. 1st ed. Prentice Hall, p.1.
2. Stephan, B. (2016). Porosity Explained – Petro Prophet: Oilfield Education. [online] Petroprophet.com. Available at: https://www.petroprophet.com/porosity-explained/ [Accessed 7 Oct. 2018].
3. Sorting. (2018). In: Schlumberger Oilfield Glossary. [online] Schlumberger. Available at: https://www.glossary.oilfield.slb.com/Terms/s/sorting.aspx [Accessed 7 Oct. 2018].

Images:

Stephan, B. (2016). Porosity Explained – Petro Prophet: Oilfield Education. [online] Petroprophet.com. Available at: https://www.petroprophet.com/porosity-explained/ [Accessed 7 Oct. 2018].