Which term describes the ability of a rock to store fluids (void space)?

• A. Permeability
• B. Specific Gravity
• C. Porosity
• D. Compressibility

Answer: (C)

Porosity describes the amount of void space in a rock, the space that can be filled with fluids. It quantifies how much fluid a rock can store when saturated and is usually expressed as a percentage or decimal of the total volume. This storage capacity is different from how easily fluids move through a rock, which is what permeability measures. Permeability concerns the connectivity of pore spaces and flow, not just how much space exists. Other terms like specific gravity relate to density, and compressibility describes how the rock volume changes under pressure. So, porosity is the term that best captures a rock’s ability to store fluids.