Synonym: Formation Volume Factor = Formation Fluid Shrinkage
Ratio of fluid volume at subsurface conditions
V_{\rm sub} to fluid volume at reference conditions
V_{\rm ref}:
| B = \frac{V_{\rm sub}}{V_{\rm ref}} = \frac{\rho_{\rm ref}}{\rho_{\rm sub}} |
where \rho_{\rm ref} is density at reference conditions and \rho_{\rm sub} 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:
| (1) | B = \frac{Z}{Z_{ref}} \cdot \frac{p_{ref}}{p} \cdot \frac{T}{T_{ref}} |
It is related to fluid compressibility c as:
| (2) | c = - \frac{1}{B} \cdot \frac{dB}{dp} |
For the slightly compressible fluid the fluid compressibility is not dependent on pressure c(p) = c = \rm const and Formation Volume Factor has a linear dependence on pressure p with usually a very small gradient c \sim 0 \Leftrightarrow c \cdot (p-p_i) \ll 1:
| (3) | B(p) = B_i \cdot [1 - c \cdot (p - p_i) ] |
where
p_i | some pressure point around which the dynamic process is happening |
B_i | Formation Volume Factor at this pressure point |
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
[ Oil formation volume factor (Bo) ][ Gas formation volume factor (Bg) ][ Water formation volume factor (Bw) ]