API PUBL 2566-2004 pdf download.State of the Art Multiphase Flow Metering.
The attractiveness of the new multiphase metering systems, operating unattended and without the need for phase separation, stemmed from their potential to avoid or overcome some of the above operational problems. Multiphase meters provide a system that can be installed subsea. In addition, these advantages can produce significant savings especially in offshore operations. The less bulky and lighter weight of multiphase meters was a major attraction for the installation offshore and therefore a significant influence in the evaluation of the technology, especially for operators in the North Sea (II-19, II- 22) and the Gulf of Mexico. The oil industry has recognized the potential benefits of the new multiphase meters (II- 10 to 16). A systematic effort was undertaken in the 90’s by several North Sea operators to identify potential multiphase metering applications, reservoir engineering needs, and meter performances for a number of asset developments in North Sea (II-22). For the past 10 years, considerable effort has gone into developing multiphase meters that can measure gas, oil, and water flow rates at wellhead conditions (II-1). These efforts have led to the development and marketing of several types of multiphase meters. In the past five years, the meter manufacturers and operators have jointly tested multiphase meters under a variety of field conditions to evaluate their performances. In the next sections of this paper, we shall look at the trends in installations of multiphase metering systems. Wet gas metering is a more recent area of development in multiphase measurements. Wet gas metering covers a variety of measurements in production streams with high to very high gas volume fractions. There is a need for direct measurement of gas under these conditions in such applications as gas condensate and high GOR fields as well as many production operations where gas from separation systems may contain liquid (III-1). The numbers of multiphase meter installed have increased steadily since the first detailed survey was published in 1997 (II-8). Figure 1 shows the trend in the number of multiphase meter installations. This Figure is based on annual surveys of commercial multiphase meter vendors (II-11, II-12, II-14, II-15, IV-30). No such surveys were conducted for wet gas meters. But an informal survey of wet gas vendors indicates that the number of installations using wet gas meters – i.e. gas metering systems that can measure gas and liquid on-line – is about 100. In the last several years the number of worldwide installations have increased substantially. Currently, there are about 1,000 multiphase meter installations in various areas around the world. While this number is a small fraction of the total number of potential well testing sites, the rate of growth has been substantial and widespread.
The initial interest in the technology was confined to offshore and subsea applications, but over half of the current installations are now in on-shore operations as shown in Figure 1. Onshore operators are using multiphase meters to reduce the cost of well testing. As we will see in the “Application” section of this report, multiphase meters can reduce the cost of well testing by reducing the time needed to conduct a well test. This allows the operator to test more wells with multiphase meters than conventional test separators, which is very important to the management of many marginal onshore reservoirs.
Two major factors have contributed to the wider spread of the technology: • Development of efficient compact separators (II-28) has resulted in the availability multiphase metering systems utilizing partial separation (off- line). In contrast to the in-line multiphase meters, which accept the full stream, the off-line systems depend on the removal of most of the gas from the liquid flow stream. The temporary separated gas and liquid streams are subjected to measurements before being recombined into the initial full stream. These off-line multiphase metering systems are less complex and still offer some, if not all, of the advantages of the in-line multiphase measurement systems – i.e. real time measurement, shorter test time, and smaller size and weight relative to traditional gravity separation vessels, but larger than multiphase meters. The development of these systems is discussed in more detail later in this report. Asia-Pacific 24% Eastern Europe(CIS) 1% Middle East 6% Africa 5% USA 25% Americas 9% Canada 0% Mobile 7% Western Europe 23% • The compact size of multiphase meters has also resulted in the deployment of mobile systems. Mobile systems have enabled operators to use the multiphase metering technique in remote regions or in operations where a conventional well testing facility would not be available. Trailer- mounted multiphase meters have been used for well testing in fields where wells are scattered over a large area (IV-10, IV-13). In the past 3 years the number of mobile systems have increased significantly.