Abstract

BP Exploration currently has an interest in hundreds of kilometres of operating multiphase flowlines. Most of the company's proposed field developments also involve multiphase flowlines. large number of these do or will experience slug flow, either as the normal flow regime, or as a result of transient behaviour.

Data on flow regime and slug flow characteristics have been collected from many lines over the past 8 years. Information on slug characteristics from a number of different systems is presented in this paper, including velocity, length and holdup. Some unfavourable consequences of slug flow on both process performance and system integrity are highlighted, including plant shutdowns and mechanical damage.

The need to be able to predict slug flow for the design of future systems, and to advise the operators of existing systems, remains a high priority for R&D activities, as ever longer and more complex multiphase systems are proposed. BP's latest slug frequency method is described, followed by guidelines for pipework layout, and comments on current R&D on corrosion in multiphase flow.

Introduction

The majority of oil and gas fields in which BP Exploration has an interest, whether currently operating, or under development, involve multiphase fiowlines. The total length of multiphase lines runs to many hundreds of kilometres. There is a wide range of lengths, diameters, and flowrates involved. In operating such a large variety of multiphase flow crude oil production systems, BP Exploration has amassed considerable experience, and data. From 4 inch lines at Wytch Farm onshore in the UK, to the 28 inch Endicott inter-island line, there are lessons to be learnt in terms of operating conditions to be avoided, and information to be used in the development and validation of improved design methods.

This paper presents a summary of this information, as it relates to slug flow in near horizontal flowlines, together with related design methods and recommendations. A brief discussion of corrosion in slug flow, an area of great significance is also given.

Slug flow has been, and remains a source of concern for designers and operators, and much effort has been put into developing an improved understanding, and design capability, for slug flow in near horizontal lines.

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