Over the last decade the development, evaluation and use of MFM systems has been a major focus for the Oil & Gas industry worldwide. So far, many alternative metering systems have been developed, but none of them can be referred to as generally applicable or universally accurate. Both established and novel technologies suitable to measure the flow rates of gas, oil and water in a three-phase flow are reviewed and assessed within this framework. Those technologies already implemented in the various commercial meters are then evaluated in terms of operational and economical advantages or shortcomings from an operator point of view. The lessons learned about the practical reliability, accuracy and use of the available technology are discussed. As operators now realise, incorporation of MFM's is an essential step in exploiting marginal fields. A new approach to flow assurance, deep water developments, downhole/seabed separation systems and wet gas fields is foreseen. The paper suggests where the research to develop the next generation of MFM devices will be focused in order to meet the as yet unsolved problems.
Brief history
The first commercial MFM's appeared about ten years ago, as a result of several multiphase metering research projects that took place in the early 1980's. Among those universities, research centres and oil companies that gave their contribution to the development of MFM's and that still are carrying out studies on the subject are: Tulsa (US), SINTEF (Norway), Imperial College (UK), National Engineering Laboratory (UK), CMR (Norway), BP, Texaco, Elf, Shell, Agip and Petrobras. The first tests of these prototype-MFM's were carried out by BP and Texaco. The driving force to develop MFM technology was the forecast decline of production from the major North Sea fields, accompanied by the necessity to tie back future smaller discoveries to existing infrastructure. Increasing gas and water fractions, inherent in a mature producing province, would create more unstable flow conditions in existing production facilities and require more flexible multiphase solutions.
In less than a decade, MFM has become accepted in the field and is beginning to be considered among the primary metering solutions for new field developments.
MFM applications
Within the oil and gas industry, it is generally recognised that MFM could lead to great benefits in terms of1,2,3:Layout of production facilities The use of MFM's reduces the hardware needed for onshore, offshore topside and offshore subsea applications. Of primary importance is the removal of a dedicated test separator for well testing applications. Utilising MFM (with its smaller "footprint") for topside applications minimises platform space and load requirements for well testing operations. Finally, costly well test lines can be stripped from the production facilities, which may be of vital importance for unmanned locations, deepwater developments and satellite fields.