The Numerical modeling of multiphase flow in the oil and gas gathering pipeline from wellhead platform of X field to central processing platform of Y field

Abstract

The main objective of this research is to investigate the characteristics of slug flow inside the riser which is a 68-meter vertical pipe segment reaching from the seabed to the central processing platform of the Y field. The oil and gas mixture flows into the riser from the wellhead platform of the X field through a 25-km horizontal subsea pipeline. In this study, an integrated modeling approach is used to take into account major physical phenomena associated with the multiphase flow in the gathering system that might have strong influences on slug flow characteristics. The phase behavior model of oil and gas in the gathering pipeline were first built on the basis of Peng-Robinson equation of state to determine the multiphase equilibria and estimate fluid properties at various pressure and temperature conditions. The multiphase flow was then modeled by Beggs & Brill method for pressure drops and Hasan & Kabir for temperature distribution along the pipeline. In particular, the pressure drop calculation is based on empirical correlations from which the flow regimes can be identified and pressure drop is determined accordingly. The heat transfer calculation, on the other hand, is based on the mechanistic approach from which the temperature distribution along the pipeline system can be estimated. Finally, the slug-tracking model was developed to characterize the slug flow with essential properties such as slug frequency, length and surge volume. This helps identify slug flow existence inside the riser segment and predict potential consequences it may cause to surface facilities. The results from this work show that the integrated modeling approach is suitable to the multiphysics nature of the flow assurance problem under consideration. The slug flow might exist in the 68-m riser where more than 20 slugs of 2-m length might occur after every 1.5 hours.