A Numerical Model for Multiphase Flow on Oil-Production Wells
- Sergio Pablo Ferro (Tenaris) | Marcela Beatriz Goldschmit (Tenaris)
- Document ID
- Society of Petroleum Engineers
- Latin American & Caribbean Petroleum Engineering Conference, 15-18 April, Buenos Aires, Argentina
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 4.2.3 Materials and Corrosion, 5.3.2 Multiphase Flow, 4.1.5 Processing Equipment, 1.10 Drilling Equipment, 5.2.1 Phase Behavior and PVT Measurements
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A numerical model for the analysis of multiphase flow on vertical or slightly inclined wells has been developed. The model calculates flow properties (velocity of each phase, volumetric fraction of each phase, pressure and fluids properties) on gas-oil-water wells as function of depth. Fluids properties are obtained under the assumption of black oil
model by means of correlations taken from literature, requiring only petroleum °API and the gas specific gravity as
The model may be applied to simulate both liquid flow and gas-liquid flow. In this case, different flow patterns are taken
into account: -bubble, slug, dispersed bubble and annulardepending on flow conditions, which are determined from fluid properties and production rates of oil, gas and water. Flow in tubings consisting of several sections with different diameters and inclinations may also be simulated.
The model was validated by comparisons of measured and calculated the pressure variation along the well Good agreement was found between the numerically predicted pressure drop and measurements taken from different
databases from open literature. As a consequence the proposed model proves to be a reliable tool to describe the
flow on oil-gas-water wells.
The developed numerical model takes into account the most relevant effects that take place in a production well including multiphase flow, presence of different flow pattern, mass transfer from gaseous to liquid phase and influence of
gas-liquid flow pattern on wall friction. Special attention is paid to the velocity profile of each phase along the well. Ishii's
model for two-fluid flow is used to prescribe the slip velocity between liquid and gaseous phases and to determine the
acceleration term contribution to the pressure gradient. This model is actually being employed for corrosion rate calculations inside production wells.
The study of the multiphase flows (water - oil - gas) is of major importance in oil industry since it is found quite frequently during the production process. The physics involved in these flows is very complex due to interactions between the different phases. In order to deal with this complexity, sophisticated numerical models with several parameters (most of them determined from experiments) are required.
The complexity of the problem leads to a number of simplifying assumptions and to the use of correlations to model some terms of the equations. Many numerical methods have been proposed in order to prescribe flow variables (velocities of each phase, volume fraction of each phase, flow pattern, pressure gradient) along the tubing for vertical upward flow. There is a wide variety of numerical methods, including simple models where liquid and gas are supposed to have same velocity [1-3], models that account for slippage between gas and liquid but do not consider the existence of different flow patterns [4-6], models that take into account different flow patterns [7-12] to complex mechanistic models [13-17].
In this work an alternative numerical model to estimate the flow characteristics along a vertical or near vertical pipe is presented. The proposed method belongs to the class of models described in references [7-12]. However, instead of using a correlation for liquid hold up we use a correlation for the slip velocity between liquid and gaseous phases and
calculate the hold up from conservation equations. It was codified in a FORTRAN code named GOWflow.
In the next section the general equations of the model are introduced. Then the modeling of different terms taking part in the equations is presented, followed by the description of the algorithm. There is a section devoted to the validation and another one to the application. In the last section conclusions and future work are discussed.
Governing equations were obtained from mass conservation for each component and global momentum conservation
principles in steady state . The equations were averaged across the -assumed circular- section S of the pipe in order to obtain a one-dimensional model.
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