As large, accessible gas and oil reserves become depleted, it is becoming increasingly more important to develop marginal fields that were once considered uneconomic. It is the responsibility of the design engineer to ensure this exploitation is both technically feasible and cost effective.
One of the preferred methods to date has been the transfer of well fluids to a central ‘production/processing’ facility via a multi- phase pipeline. In this context multi-phase may not only be oil and gas but also water and solids, thus adding further complications to the understanding of fluid behaviour/characteristics and consequently the system design. The aim of this paper is to address some of the important process engineering design aspects of multi-phase flow systems specifically for use on marginal field developments. Typical examples of such aspects include:-
The accurate prediction of flow regime, pressure and temperature drops, liquid holdups, hydrodynamic slugging in pipelines and severe slugging in risers;
Hydrate formation and inhibition requirements;
Waxing, emulsion, scaling, corrosion and erosion.
Such information is vital for the complete design of the multi-phase pipeline, its capacity and associated process equipment. Our practical experience in this specific area, supported by examples from a selection of recently completed projects, are presented.
The principal objective of this paper is to provide a platform to stimulate further discussion and give input from others' experience, and also provide a general overview of the critical issues that need to be addressed to achieve successful designs for such developments.
With the gradual decline in the manageable reserves of existing fields, more emphasis is being placed on the development of smaller, leas accessible fields, which were once considered uneconomic.
The size of these marginal fields minimise their ability to bear the cost of dedicated production facilities. This has motivated oil companies to invest heavily in the search for more economic methods for the exploitation of these undeveloped fields. Multiphase transportation can make marginal Fields economical and extend the life of existing platform production facilities.
The transportation of gas and oil two base fluid or gas, oil and water (three phase liquid) simu1taneously in large diameter pipelines over relatively long distance required a detailed understanding of multiphase 1ow phenomena.
It is the aim of this paper to briefly outline the important steps that should be followed prior to final design submittal, whilst highlighting indirect consequences of multiphase transportation.
During the discussion we shall emphasise the importance of accurate steady state analysis covering the fundamental aspects of steady state multi-phase flow with typical examples to highlight the following:-
pressure drop;
temperature;
liquid hold-up;
hydrodynamic/terrain induced slugging, and
severe slugging in risers
In addition to the initial steady state analysis, this paper also aims to highlight the importance of considering transient phenomena when designing multi phase systems, addressing some of the more interesting effects of transient operation, including:-
system start-up and shutdown;
cool-down; and
production upsets.
