Implementation of multiphase metering on unmanned wellhead platform
Authors: Couput Jean Paul , Prouvost Hubert , Coquil Marc , Leporcher Emile , Dykesteen Eivind 
Published: October 2008

In 1997 TotalFinaElf installed a multiphase meter on an offshore unmanned wellhead platform in the Middle East. The decision to go for the multiphase metering alternative, rather than a test separator, was based on the potential high savings in CAPEX and OPEX. Monitoring of the multiphase flow at the wellhead eliminates the need for dedicated testlines from remote wellhead completions, as well as the need for a dedicated test separator at the processing facility. At this field, the deployment of a multiphase meter has contributed in improving the economy of the full project and improving our understanding of the hydrodynamics of the reservoir near the wellbore. This experience demonstrates that MPFM can be a very reliable solution for well testing and well monitoring; nevertheless success requires a minimum involvement of all people (project people, specialists, users) from design studies to operations.

Introduction

At the beginning of the 90's, TotalFinaElf launched a major research and development project to extend the capabilities of multiphase export. This program included the simultaneous development of multiphase flow modeling, multiphase technology (qualification of multiphase pumps, development of multiphase meters, subsea separation), and a new process to fight fluid-related effects such as hydrates, waxes, etc.

The initial aim was to simplify surface topside facilities; to avoid installation of separators, pumps, compressors, and safety/flaring systems. In a second stage, this technology could be subsea deployed. The development of these different disciplines would help to avoid duplicate processing and huge infrastructures, and would ease remote controlled operation of unmanned platforms. The multiphase meter was one component of this global approach.

From 91 to 96, TotalFinaElf supported and tested multiphase meter prototypes. These were qualified on onshore fields. The application of an integrated multiphase approach to develop a Middle East offshore field reduced the investments and operating costs drastically. In such a development, the multiphase meter found its place by eliminating the need for a dedicated testing flowline or a test separator and flaring system. Therefore, in 1997 TotalFinaElf installed their first multiphase meter on an offshore unmanned wellhead platform. This paper describes the field facilities, the implementation of the multiphase meter, the operating conditions, and the experience gained and lessons learned about this equipment compared to test separators.

The application

The decision to use a multiphase meter was made back in 1994/1995. At that time, very few fields relied on a multiphase meter for well testing, without it being backed up by a test separator.

The field layout is shown in Figure 1, and comprises wells that are clustered on a wellhead platform. The production is sent on shore through a 40 Km line. After separation, the oil is metered before custody transfer, which yields an excellent reference measurement.

The platform is unmanned. It has minimum facilities: Production manifold, test manifold and the multiphase meter MPFM 1900VI. The local operator interface of the meter is housed in the electrical room.