Slug flow continues to be a disruptive influence on both design and operation of multiphase pipelines and risers. In the past, the focus was largely on slugging cycles driven by the riser or driven by large scale terrain effects which were ultimately accommodated through slug catcher design, gas lift deployment, passive or active slug control measures. The current challenge is to resolve the much higher frequency hydrodynamic slug flow in order to support fatigue analysis within mechanical design of free spans, and risers, which have low tolerance to cyclic loads.
This paper will examine the use of tools capable of predicting the formation of hydrodynamic slugs within a production system and following their evolution with length and interaction with terrain. The challenges of routine deployment of such methods in support of design or operations will be considered.
In the past, the need for modelling slug flow was largely focussed around modelling severe slugging cycles and large scale liquid movement events due to restart, ramp-up or pigging, in order that the behaviour could be aligned with the capability of the downstream process plant. Such slugs, and event driven liquid movement, may be accommodated using large vessels, mitigated through operating procedures which change the system in a more gradual manner, or managed using gas injection or other active or passive slug control systems .