Permeable

Permeability refers to the ability of a material to allow another substance to pass through it, especially the ability of a porous rock, sediment, or soil to transmit fluid through pores and cracks. Geologic permeability can be either primary or secondary. Primary permeability is determined by the size and shape of the rock grains and the packing of the grains. Secondary permeability is caused by fractures and cracks in the rock.

Types of Permeability

There are two types of permeability: absolute and effective. Absolute permeability is the measure of the permeability of a rock without any fluid interactions. Effective permeability is the ability to preferentially transmit a particular fluid when other fluids are present in the rock.

Factors Affecting Permeability

Several factors can affect the permeability of a substance. These include the porosity of the material, the viscosity of the fluid, and the pressure gradient across the material. The size, shape, and distribution of the pores in the material also play a significant role in determining its permeability.

Measurement of Permeability

Permeability is typically measured in the lab using a permeameter. The unit of measurement for permeability is the darcy (D), named after the French scientist Henry Darcy who first described the flow of water through sand.

Applications of Permeability

Permeability has many applications in various fields. In hydrogeology, it is used to determine the flow of water in aquifers. In petroleum engineering, it is used to calculate the flow of oil and gas in reservoirs. In civil engineering, it is used to design and analyze the stability of soil structures.

See Also

• Hydraulic conductivity
• Infiltration (hydrology)
• Permeation
• Porosity
• Transmissivity