An eulerian-eulerian approach for oil&gas separator design conference Paper

LIST of SYMBOLS 
-
𝛼
𝑘
: phase fraction; 
-
𝒗
̅
𝒌
: phase-average velocity; 
-
𝜌
𝑘
: phase density; 
-
𝑝̅
and 
𝑝̅
𝑟𝑔ℎ
: phase-average pressure and phase-average modified pressure; 
-
𝑴
𝑰,𝒌𝒋
: 
momentum exchange across interface between phase 
k 
and phase 
j
; 
-
𝑹
𝒌
𝒆𝒇𝒇
:
 
combined Reynolds (turbulent) and viscous stress;
 
-
𝐶
𝑑
: 
drag coefficient; 
-
𝐶𝑑𝑅𝑒
: product of drag coefficient and particle Reynolds number; 
-
𝑅𝑒
𝑝
:
particle Reynolds number
; 
-
𝑑
𝑘
: 
particle diameter;
 
-
𝜈
𝑘
: phase kinematic viscosity; 
-
𝑘
𝑘
: turbulent kinetic energy; 
-
𝜀
𝑘
: dissipation rate; 
-
𝜈
𝑘
𝑡
: turbulent kinematic viscosity; 
-
𝐶
𝑡,𝑘𝑗
: turbulent response coefficient of phase 
k
with respect to phase 
j
; 
-
𝑉
𝑡,𝑘𝑗
: terminal velocity; 
-
𝐠
: acceleration field;
 

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2 
INTRODUCTION
Nowadays, multiphase flows can be considered as the standard condition for the majority of the
Oil&Gas production fields. The reasons for this peculiarity are numerous and can be related to 
different parts of the hydrocarbons production chain. As an example, injection of fluids to sustain 
production as well as the presence of an active gas cap or an aquifer determine the existence of at 
least two different phases in the upcoming flow streams. Moreover, the difference in pressure 
between the wellbore and the production tubing determines the production of a certain (and in many 
cases non negligible) amount of gas (if the bubble point condition is reached) and the possible arising 
of non-ideal volumetric behaviors (e.g., retrograde condensation). 
Among the different challenges deriving from the inherent multiphase nature of the upcoming 
reservoir flows, a key issue is represented from the separation process that the fluids must 
undertake. 
In the present paper, a consistent CFD framework for handling the separation process that occurs 
in an oil&gas separator is presented. This framework can be essentially divided in two parts: 
1. A simplified geometry for an oil and gas separator that find a compromise between the 
requirements in term of mesh generation and computational analysis and the possibility to 
provide suitable information concerning the internal fluid-dynamics; 
2. An Eulerian-Eulerian three-phase solver able to capture the separation and assess its 
efficiency. Moreover, a proposal of a three-phase turbulence model has been included to 
close the system of equations without exceeding the computational cost; 
The principle mean of investigation is represented by the OpenFOAM, a C++ software based on the 
object-oriented programming. The open-source nature of this tool alongside with the vast multiphase 
library already implemented makes it ideal for the development, customization and optimization of 
new solvers.