Black-oil fluid model¶

Overview¶

In the black-oil model three pseudo-components, oil (o), gas (g) and water (w) are considered. These are assumed to be partitioned across three fluid phases, named liquid (l), vapor (v) and aqueous (a).

Phase behavior is characterized by the following quantities which are used to relate properties of the fluids in the reservoir to their properties at surface conditions.

$B_o$ : oil formation volume factor
$B_g$ : gas formation volume factor
$R_s$ : gas/oil ratio
$R_v$ : oil/gas ratio

By tables, that tabulate saturated and undersaturated oil and gas properties as functions of pressure and solution ratios.

Dead oil¶

In dead-oil each component occupies only one phase. Thus, the following partition matrix determines the components distribution within the three phases:

$\begin{bmatrix} y_{gv} & y_{gl} & y_{ga}\\ y_{ov} & y_{ol} & y_{oa}\\ y_{wv} & y_{wl} & y_{wa} \end{bmatrix} = \begin{bmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix}$

and the phase densities are

$\rho_{l} = & \, \frac{\rho_{o}^{STC}}{B_{o}} \\ \rho_{v} = & \, \frac{\rho_{g}^{STC}}{B_{g}}.$

Live oil¶

The live oil fluid model make no assumptions about the partitioning of the hydrocarbon components and the following composition matrix can be used

$\begin{bmatrix} y_{gv} & y_{gl} & y_{ga}\\ \\ y_{ov} & y_{ol} & y_{oa}\\ \\ y_{wv} & y_{wl} & y_{wa} \end{bmatrix} = \begin{bmatrix} \frac{\rho_{g}^{STC}}{\rho_{g}^{STC} + \rho_{o}^{STC} r_{s}} & \frac{\rho_{g}^{STC} R_{s}}{\rho_{o}^{STC} + \rho_{g}^{STC} R_{s}} & 0 \\ \\ \frac{\rho_{o}^{STC} r_{s}}{\rho_{g}^{STC} + \rho_{o}^{STC} r_{s}} & \frac{\rho_{o}^{STC}}{\rho_{o}^{STC} + \rho_{g}^{STC} R_{s}} & 0 \\ \\ 0 & 0 & 1 \end{bmatrix}$

whereas the densities of the two hydrocarbon phases are

$\rho_{l} = & \, \frac{\rho_{o}^{STC} + \rho_{g}^{STC} R_{s}}{B_{o}} \\ \rho_{v} = & \, \frac{\rho_{g}^{STC} + \rho_{o}^{STC} R_{v}}{B_{g}}$

See Petrowiki for more information.

Parameters¶

Both types are represented by <BlackOilFluid> node in the input. Under the hood this is a wrapper around PVTPackage library, which is included as a submodule. In order to use the model, GEOSX must be built with -DENABLE_PVTPACKAGE=ON (default).

The following attributes are supported:

Name	Type	Default	Description
componentMolarWeight	real64_array	required	Component molar weights
componentNames	string_array	{}	List of component names
fluidType	geosx_constitutive_BlackOilFluid_FluidType	required	Type of black-oil fluid. Valid options: * DeadOil * LiveOil
name	string	required	A name is required for any non-unique nodes
phaseNames	string_array	required	List of fluid phases
surfaceDensities	real64_array	required	List of surface densities for each phase
tableFiles	path_array	required	List of filenames with input PVT tables

Supported phase names are:

oil
gas
water

Example¶

<Constitutive>
  <BlackOilFluid name="fluid1"
                 fluidType="LiveOil"
                 phaseNames="oil gas water"
                 surfaceDensities="800.0 0.9907 1022.0"
                 componentMolarWeight="114e-3 16e-3 18e-3"
                 tableFiles="pvto.txt pvtg.txt pvtw.txt"/>
</Constitutive>