Volumetric value of Oil In Place (OIP) recalculated to NTP conditions:

V_{\rm STOIP} =  \int_{\Omega} \left[ \frac{s_o({\bf r}) }{B_o} + \frac{R_v \, s_g({\bf r})}{B_g}  \right]  \phi_e({\bf r}) dV

where

	Petroleum reservoir
	Position vector to some location in a reservoir
	Volume element of a reservoir
	Initial formation pressure and temperature at location
	Effective porosity at location
	Current Oil saturation and Gas saturation at location
	Oil FVF and Gas FVF at Initial formation pressure and temperature
	Solution GOR and Vaporized Oil Ratio at Initial formation pressure and temperature

For practical implementation of one needs to build a Dynamic Flow Model (DFM) and perform a numerical integration.

See Also