What is STOIIP or OOIP ?

The full form of these two abbreviations are as follows:

• STOIIP = Stock Tank Oil Initially In Place
• OOIP = Original Oil In Place, or
• STOOIP = Stock Tank Original Oil In Place

All of the above, essentially mean the volume of oil originally or initially present in a hydrocarbon reservoir expressed in equivalent volume that it would occupy in a stock tank at standard temperature and pressure.

Mathematically, it is expressed as:

STOIIP = BV *ϕ * (1-Swi) / Bo

where,
BV = Bulk Volume of the Reservoir
ϕ = Porosity (need to be Effective Porosity)
Swi = Initial Water Saturation
Bo = Formation Volume Factor