Which term refers to the depth of a petroleum product in a tank?

The term that refers to the depth of a petroleum product in a tank is "innage." Innage specifically measures the vertical depth of a liquid in a tank from the surface of the liquid to the bottom of the tank. This measurement is critical in tank operations to determine how much product is available and to ensure safe handling and storage of petroleum products.

In contrast, ullage refers to the void space above the liquid level in the tank. It is important for assessing total capacity and for accommodating thermal expansion of the liquid. Thievage is the practice of taking samples of the product or measuring the level at specific points and doesn’t directly refer to the depth of the liquid itself. Outage typically indicates the difference between the tank's total capacity and the actual amount of product in the tank, which does not specifically address the depth of the petroleum product.