Stock-tank Oil Initially in Place
Definition - What does Stock-tank Oil Initially in Place mean?
Stock-tank Oil Initially in Place (STOIIP) is the total amount of crude oil present in a hydrocarbon reservoir before the commencement of any production. As it is not possible to measure the total volume or exact quantity of the oil in the hydrocarbon reservoir, other parameters are considered and studied for any judgment of oil estimation. It is also known as Oil in Place (OIP) and Stock Tank Original Oil in Place (STOOIP).
Petropedia explains Stock-tank Oil Initially in Place
Stock-tank Oil Initially in Place is the volume of oil present in a hydrocarbon reservoir before the start of any production in equivalent volume that the oil will occupy when it is stocked in a storage tank. In mathematical terms, STOIIP can be expressed as:
STOIIP = BV x F x (1-Swi) / Bo,
BV = Reservoir Bulk Volume
F = Effective porosity of the oil bearing rock
Swi = Initial water saturation
Bo = Volume correction factors
In order to estimate the oil in place or initial quantity of oil in a reservoir, volumetric methods are used. An estimation of the size of the oil bearing rock is made by conducting a series of test drills at nearby locations and based on the results rock conditions are mapped.