High-Performance Multiphase Metering: A Personal Perspective

Multiphase meters have been seen by many engineers as key components in reducing the capital and operational costs of oil and gas production facilities. The development has been targeted essentially at improving well testing replace a large and expensive test separator by a compact cheap multiphase meter with equivalent perfonnance and you have obvious savings. For subsea applications the savings are even larger subsea mu1tiphase meters mounted at the wellheads save long test lines. Yet despite the potential benefits oil companies are only slowly deploying multiphase meters. Indeed, with the recent fall in oil price and the subsequent cut-backs, there has been a large reduction in funds for development of multiphase meters. I have argued that the greatest savings from using multiphase meters will come when their perfonnance is sufficiently good for them to be used for third-party allocation and when they are deployed subsea. This is especially true for a highcost production area such as the North Sea. One can then run multiphase pipelines from subsea satellites to the most convenient host facility where the hydrocarbons can be processed in common separation facilities. Thus one avoids the problem of juggling the production to the separators available to allow reasonably accurate allocation. I do not think it is exaggerated to say that without high-perfonnance multiphase metering it will simply not be economically worthwhile for oil companies to develop the small accumulations of hydrocarbons left in the North Sea. Of course they could agree to exchange or sell acreage, or agree to lower-quality metering and get around the problem, but this has not been popular to date. Knowing what one is doing is crucial for the successful exploitation of marginal fields. Cost-effective measurements are not 'nice to have'; they are essential to minimise the hassle inherent in taking on these developments, and in optimising the production. How realistic is my claim that highperfonnance multiphase metering is not only practicable, but can be achieved in reasonable time-scales, say 5-10 years? In some special cases, such as wet-gas metering, we have already achieved that kind of perfonnance. In several cases where we have operated multiphase meters in series with test or production separator metering, the multiphase meters have shown that the separator metering is mostly not as good as we would like to believe. The logic is simple: if you are happy with traditional separator metering, you should also be prepared to be happy with the multiphase metering. Laboratory tests show that there are clear ways to improve the meters' perfonnances, but also show up deficiencies in the test facilities. It is easy to bemoan the fact that mu1tiphase meters, after some twenty years of development, are not yet widely in use. On the contrary, it is a great tribute to all involved that we have meters that can be deployed, can already compete with traditional metering systems and have brought savings to the industry that easily exceed the total cost ofdevelopment to date. I see no good technical reasons why the perfonnance of multiphase meters should not improve to near fiscal quality. Multiphase metering presently offers a wide range of choices for field development or upgrading facilities, but these are poorly tested and cannot be proved except on operating facilities. In its current approach to reducing costs, the industly would like to have the benefits but is unwilling to invest the money to ensure satisfactory implementation. The oil and gas producers appear to hope that multiphase metering has become sufficiently mature so that only indirect support is needed. This paper discusses how to approach multiphase metering applications; the needs for multiphase metering; application areas with the emphasis on high perfonnance; difficulties of implementation; and the future of multiphase metering, with the emphasis on high perfonnance.