ABSTRACT:

At Ripalta, Italy, the natural gas stocked in an exhausted reservoir is dehydrated before its input into the gas network. Normally the liquid carry over from these columns is 1.3 Kg/106 Sm3. This could be a hundred times greater in case of malfunctioning. In order to monitor the liquid carry over, STOGIT decided to install a wet gas meter based on isokinetic sampling. This type of flow meter has been used in the past by ENI E&P for another challenging application: the measurement of a liquid volume fraction about equal to 0.2% and a water fraction about equal to 0.02% in the Allegheny TLP (Gulf of Mexico) [1]. At Ripalta the natural gas flows in a 12" pipeline at 40-50 Bar of static pressure. Due to the size of the pipeline, for the first time it was decided to install the flow meter in a horizontal configuration. The innovative design of the horizontal multiphase flowmeter allowed a very compact dimension: 1.8m in length and 1.5m in height. The meter was installed on February 2006. A preliminary set of test was made by injecting known quantities of liquid during the normal process. The results obtained without performing any type of calibration were excellent: The meter was able to detect liquid when the liquid volume fraction was 0.00002% with a scatter between injected and measured liquid flow rates equal to or less than 10% relative. To our knowledge it is unique that a multiphase meter is able to work under these conditions. The instrument is now being operated by STOGIT. STOGIT has also installed a second instrument in another gas plan

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