Fahad B. A. Almudairis (Doctor of Philosophy in Petroleum Engineering)
Unified Transient Model for Gas-Oil-Water Flow in Wells and Pipelines
Conclusions and Recommendations
Many transient phenomena are encountered in the oil industry during daily operations. In a production system, transient multiphase flow can be initiated from production rate change, sudden perturbation of steady-state flow, or due to special pipeline geometries such as severe slugging in pipeline-riser system and developing slug flow in hilly-terrain pipelines. Operating a well or a pipeline under these transient conditions can cause significant production fluctuations, and reduce the efficiency of the production system. Therefore, these transient operation processes need to be predicted and analyzed.
This study presents a three-phase gas-oil-water model for the simulation and analysis of various steady-state and transient production processes. In three-phase flow, when the two liquids are separated, the two-phase models cannot be used, and new flow patterns are formed. The new transient mechanistic models are developed based on mass and momentum conservation principles for each flow pattern. The partial differential equations are solved using the finite difference method for both spatial and time discretization. A new solution algorithm is adopted to achieve a stable and full transient model. The flow patterns are determined based on two-phase gas-liquid flow pattern transition criteria along with the oil and water mixing status.
The fluid properties at each time step are calculated using either black oil or compositional model. The additional variables are calculated using closure relationships.
The present model can predict the detailed multiphase flow hydrodynamic behaviors including pressure, temperature, local flow pattern, liquid holdup, and fluid velocities. The present simulator is comprehensive and can be used for various transient phenomena. Moreover, practical situations are considered, including complex pipeline and wellbore geometries, and a wide range of operating conditions. The model is validated through comparisons with experimental results and commercial software simulations.