Introduction

Gas-liquid two-phase flow occurs in both onshore and offshore crude oil and natural gas production and transportation facilities. In an offshore oil and gas production facility, pipeline-riser systems are required to transport two-phase hydrocarbons from subsurface oil and gas wells to a central production platform. Severe slugging reaching several thousands pipe diameters may occur when transporting gas and liquid in these pipeline-riser systems.

Severe slugging creates potential problems in the platform facilities, e.g. separators, pumps and compressors. Severe slugging may cause overpressurization of the separator, rupture of the pipe, and an increased back pressure at the wellhead. All of these might lead to the complete shutdown of the production facility. Therefore, the accurate predictions of severe slugging characteristics, e.g. slug length, oscillatory period, are essential for the proper design and operation of two-phase flow in the pipeline-riser systems.

LedaFlow is a new dynamic multiphase flow simulator for wells and flowlines. Based on models that are closer to the actual physics of multiphase flow, LedaFlow provides a step change in fidelity, quality, accuracy and flexibility over current generation multiphase flow simulation technology. This increase in model definition provides the engineer with much greater understanding of the flow in wells and pipelines.

First of all, the experimental data acquired at IMFT published by J.Fabre and L.L. Peresson was used to validate Ledaflow 1.3 software. The same experimental results were obtained using the numerical simulation by Ledaflow.

A full updated tutorial (12/03/2013) of the new version 1.3 of Ledaflow has been created.

Then, the focus was on three points with small gas and liquid flow rates referring to J.Fabre and L.L Peresson article. Three Turndown curves were traced for each point with the same gas and liquid mass fraction but with different gas and liquid flow rate.

Using these curves and transient simulations by Ledaflow, a flow map was created to distinguish the stable zone, the transient zone and the unstable zone (severe slugging).

Studies were made to compare the geometry effect on the results already found, once by doubling the length of the pipe by two and another time by doubling the height of riser by two. 

The next Video was filmed at LISBP, INSA Toulouse for an experimental installation to capture the severe slugging phenomena.