What factor is most directly related to the rate of production from a subsurface reservoir?

The rate of production from a subsurface reservoir is most directly influenced by permeability. Permeability refers to the ability of a rock or sediment to transmit fluids through its pore spaces. In other words, it describes how easily a fluid can flow through the interconnected spaces within a material. Higher permeability indicates that fluid can move through the reservoir more freely, which enhances the production rate of resources such as oil, natural gas, or groundwater.

While factors like viscosity—how thick or sticky a fluid is—porosity, which measures the amount of open space in the material, and fluid pressure also impact production indirectly, permeability plays a critical role in the actual movement of fluids. A reservoir might have high porosity, enabling it to store a significant amount of fluid, but if it has low permeability, the fluid cannot flow efficiently to the production wells. Therefore, the actual extraction rate of resources will primarily depend on the permeability of the reservoir material.