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API RP 86:2005 pdf download

API RP 86:2005 pdf download.API Recommended Practice for Measurement of Multiphase Flow.
Other categories of multiphase flow meters include advanced signal processing systems. which estimate phase fractions and flow rates from analysis of rapidly varying signals from sensors in the multiphase flow line. Such sensors may be acoustic, pressure. differential pressure, or other types. The signal processing may be a neural network, or another form of pattern-recognition or statistical signal-processing system. for example. An example of such a system is described by Toral IBiblio. 13].
There are also multiphase metering systems which have been developed on the basis of process simulation programs combined with techniques for parameter estimation. Instead of predicting the state of the flow in a pipeline at the point of arrival, its pressure and temperature can be measured at the arrival point and put into the simulation program. The pressure and temperature of an upstream or downstream location also have to be measured. When the pipeline configuration is known along with properties of the fluids, it is possible to make estimates of phase fractions and (low rates.
It is impossible to give absolutely definitive advice for selecting multiphase flow meters from the information provided on these few pages. However, it is crucially important that potential users attempt to predict the environment in which the meter will operate during its lifetime, to as great an extent as possible. To assist in this activity, it is strongly recommended that the so-called “trajectories” of the flow expected through the meter during its lifetime be quantified by the user as accurately as is possible, and that the results be plotted on maps such as those shown in Figures 5.6 and 5.11. These flow and composition maps should then be shared among partners. meter vendors, and regulatory authorities. Such actions will result in a higher likelihood that the meters the user selects for the task will ultimately satisfy his measurement needs.
When the choice of meters has been narrowed to a few, plotting the expected trajectories of the well(s) and the known or measured operating characteristics of the meters in forms such as those shown in Figures 82. 8.3, and 8.4 can indicate which meters are likely to perform best for the application at hand.
Additionally, it should be pointed out that, in some instances, parameters that have been described as if they are constant over long period.s may actually fluctuate considerably over shorter time frames. For example, in certain circumstances slug flow may occur, with instantaneous GVF ranging from 0 — 99%, hut with an average GVF of 90%. A meter optimized for 90% may have difficulty during those times when the extremes in GVF are being experienced.
8 Measurement Uncertainty of Multiphase Flow Measurement Systems
Measurement uncertainty performance is a primary consideration in selection among various approaches of multipliase flow measurement for regulatory compliance and revenue exposure.
Unccrtainty in flow mcasuremcnt arises from the variability (or uncertainty) in one or more factors, e.g. the fluid properties, flow regime, flow rate, instrumentation, and quality of the measurement model. Multiphasc flow meters measure unprocessed fluids with two or more phases simultaneously, thereby increasing the complexity of the measurement equations and model. This model is sensitive to the relative proportions of each phase, to the properties of the fluid (particularly fluid density), and to the flow regime.
Uncertainty in multiphase flow meters is mainly due to changes in process conditions, fluid properties. flow models, measurement devices, and sensors. The impact of these uncertainties on the uncertainty of each phase typically increases considerably as the water liquid ratio (WLR), gas volume fraction (GVF) and multiphasc flow rate approach their limits.
Characteristically multiphase meter uncertainties are larger than those from single-phase meters used on properly separated streams. Furthermore, they may contain significant bias components. resulting in overall phase uncertainties which are much greater than the aforementioned single-phase measurement uncertainties. Acceptable measurements and uncertainties are achievable in the main areas of application by careful selection of a metering system based on analysis of uncertainty and sensitivity for the forecast production. Regular maintenance, calibration, and updating of the meter configuration to suit the actual fluid properties and production, contribute in equal part to minimization of uncertainty in service.


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