Critical Review of Wet Gas Definitions

摘要

Although each of the above attempts to classify wet gas covers a true aspect of wet gas, none of them can be considered as universal and self-sufficient. Due to the complexity and peculiarity of wet gas flow, it is extremely difficult to capture the effects of operating pressure and temperature, composition, flow regime, mass flow rates and volume flow rates in a single definition. Among the factors that make wet gas difficult to classify are: 1. the occurrence of slip between the liquid and the gas; 2. the difficulties in predicting the transition between flow regimes in horizontal and in vertical currents; 3. the uncertainties related to the PVT characterisation of wet and retrograde gas fields; 4. the liquid phase of wet gas streams may be a combination of hydrocarbons and water, so that wet gas metering becomes a three-phase problem; 5. the oil/water inversion point can have a significant impact on the multiphase flow correlations used to calculate pressure drops and boundaries between flow regimes; 6. solids or chemicals may be a "fourth phase" present in the stream; 7. the composition of the stream to be metered may vary with time, along with the operating pressure and temperature and, ultimately, the flow regime. Hence, a gas which is initially dry becomes a gas condensate, with the heavier components in the liquid phase and the lighter components in the gas phase.