Porosity

Porosity is the fraction of a material’s bulk volume occupied by pores or other void spaces. In rocks, it describes how much space is available to hold fluids or gases.

Pore: A small cavity or channel within a solid material. Pores are the voids whose volume porosity measures.
Intergranular porosity: Porosity located in spaces between sediment grains. These spaces commonly provide pore volume in clastic sedimentary rocks.
Petroleum reservoir: A subsurface rock formation that stores and transmits oil or natural gas. Reservoir porosity sets how much hydrocarbon the rock can store.
Void ratio: The ratio of void volume to solid volume in a porous material. Unlike porosity, void ratio divides void volume by solid volume, not bulk volume.
Total porosity: The fraction of bulk volume occupied by all pores, whether connected or isolated. It counts every void, including pores fluids cannot enter.
Fracture porosity: Porosity created by cracks and fractures in rock. Fractures add void space and can connect otherwise isolated pores.
Aquifer: A permeable geological formation that stores and transmits groundwater. Porosity contributes to the amount of water an aquifer can contain.
Specific yield: The fraction of a saturated material’s total volume that drains under gravity. It measures drainable water rather than the full volume of pores.
Effective porosity: The fraction of bulk volume occupied by interconnected pores accessible to fluids. It excludes isolated pores that contribute to total porosity but not fluid flow.
Vuggy porosity: Porosity formed by relatively large cavities within rock. Dissolution can create large voids that contribute substantially to total porosity.

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