Wet Gas Performance of Differential Pressure Flowmeters Available to Purchase

Wet gas flow measurement is becoming vital to the natural gas production industry. New wells with marginal outputs cannot justify gas-liquid separation equipment and must transfer gas which contains some liquid volume. The flow measurement device on each well dictates the allocation earnings and must therefore provide gas flow measurement as accurately as possible. Several types of differential pressure based flowmeters are currently being used in wet gas flow measurement. DP based flowmeters share many performance characteristics in wet gas applications. However, studies have also found that there can be significant differences in the correlations between meter over reading and liquid content depending of the type of DP meter being tested. Emerson Process Management conducted a series of wet gas tests on a standard orifice plate, a V-Cone, a Venturi and two Rosemount conditioning orifice plates at the National Engineering Laboratory in Scotland (NEL). Previously, tests of conditioning orifice plates in wet gas were conducted at the Colorado Engineering Experiment Station, Inc. (CEESI). The work described in this paper is aimed at investigating the similarities and differences in the performance of these meter types in wet gas flows. Comparisons of these data to those from previous studies on the meter types tested are presented. Also, as a result of these studies, a general method for correcting the over-reading of DP-based, wet gas flowmeters using process measurements and the flow computing capabilities of modern multivariable DP transmitters was developed and is presented.