Phase envelope graph

The Hydrocarbon Dewpoint Curve displays the hydrocarbon gas pressure versus its temperature. The graph has 3 areas, where the gas can be in a gas state, a mixture of gas and liquid state, or a liquid state.

1. The left-hand side of the curve is a single-phase liquid region.

2. The middle side of the curve is a two-phase gas-liquid region.

3. The right-hand side of the curve is a single-phase gas region.

Phase Envelope

The black curved line on the graph, divides the single-phase region from the two-phase gas-liquid region.

Cricondentherm

The maximum temperature (in temperature units), at which the hydrocarbon gas will start to condense out of the gaseous phase. The cricondentherm is the furthest point to the right on the phase envelope graph. It is expressed in temperature units.

Cricondenbar

The maximum pressure (in pressure units), at which the hydrocarbon gas, will start to condense out of the gaseous phase. The cricondenbar is the highest point on the phase envelope graph and is expressed in pressure units.

Critical Point

The critical point is a point on this curve where the 3 phases (gas, gas-liquid and liquid) coexists.

Hydrocarbon Dewpoint

The hydrocarbon dewpoint is the point on this curve closest to the meter's current pressure and temperature.

Operating Point

The current pressure and temperature of the gas.

Notes: The cricondentherm is stored in the gas quality (GQ) history tables, and the hydrocarbon dewpoint is stored in the Meter History (Meter History) table.

The critical point, the cricondenbar, and the phase envelope graph are not stored, and are calculated upon demand.

The phase envelope, critical point, cricondentherm, and cricondenbar are properties of the GQ and are independent of the flowing pressure and temperature conditions of the meter.