Automatic System for Measuring Gas Stream Velocity in Gas Collection System Flow-Lines

Abstract

When transporting raw gas through the gas collection system flowlines, moisture in the gas facilitates formation of hydrates during winter, which is not just impairs efficiency of gas transportation from well to gas treatment unit, but also may lead to an emergency. To prevent hydrate formation, special inhibitors are added into the gas stream, usually methanol-water solution (MWS) of a certain concentration. The process of methanol carry-over with production fluid is rather complex, as it is a two-phase mixture whose phases have different mechanism of interaction with methanol. To estimate the period after which a necessary methanol concentration is achieved throughout the length of the pipeline, one shall know the gas stream velocity in the flowline. This paper proposes to determine it from velocity of a pressure wave, which is artificially created by receiver when introducing the MWS into the stream. Fast-response pressure transmitters and recorders are used to register pressure changes, while operation of the system as a whole is synchronized with the help of GPS signals. Identification of the artificial wave proceeds following a special signal processing algorithm for pressure transmitters. Application of the system allows increasing efficiency of gas field control.