Synonym: Formation Volume Factor = Formation Fluid Shrinkage

Ratio of fluid volume at subsurface conditions  to fluid volume at reference conditions :

B = \frac{V_{\rm sub}}{V_{\rm ref}} = \frac{\rho_{\rm ref}}{\rho_{\rm sub}}

where  is density at reference conditions and  is density at subsurface conditions.

The reference conditions usually refer to SPE Standard Conditions (STP) but in some cases nay refer to separator conditions.

It can be calculated via Z-factor as:

B = \frac{Z}{Z_{ref}} \cdot \frac{p_{ref}}{p} \cdot \frac{T}{T_{ref}}

It is related to  fluid compressibility  as:

c = -  \frac{1}{B} \cdot \frac{dB}{dp}

For the slightly compressible fluid the fluid compressibility is not dependent on pressure   and Formation Volume Factor has a linear dependence on pressure  with usually a very small gradient :

B(p) = B_i \cdot [1 - c \cdot (p - p_i) ] 

where

The FVF values are usually used to recalculate the fluid volumes measured at surface to the fluid volumes which are produced from or injected to subsurface reservoir.

The most popular FVF are:

See Also

Petroleum Industry / Upstream / Subsurface E&P Disciplines / Fluid Analysis (PVT) / Dynamic fluid properties

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