Therefore it will not form any liquids, which are at times referred to as NGL (natural gas liquids). When it is produced to the surface, it is maintained in the gaseous phase with surface temperature falling outside the two-phase envelope. It contains primarily methane with small amounts of ethane, propane, and butane, with little or no heavier compounds. 1.5.1 Dry- and Wet-Gas Phase BehaviorsР”Р„s discussed earlier in this chapter, dry gas is in the gaseous phase under reservoir conditions, as marked by point A in Figure 1-7.

Р”В¬ricondenbar-the highest pressure at which a liquid and vapor can coexist.Р”В¬learly, the natural gas phase envelope can be very different depending on its source.

That means the mixture will be gas irrespective of pressure when the temperature is larger than cricondentherm.

Р”В¬ricondentherm-the highest temperature at which liquid and vapor can coexist.

The pressure and temperature at the critical point are called critical pressure and temperature, respectively. At that given pressure and temperature, gas properties are identical to liquid properties. Р”В¬ritical Point-the point on the phase envelope where the bubble point curve meets the dew point curve.It is the connected points of pressure and temperature at which the first liquid droplet is formed out of the gas phase.

Р”Вew Point Curve-the curve that separates the pure gas phase from the two-phase region.This means that at a given temperature, when pressure decreases and below the bubble point curve, gas will be emitted from the liquid phase to the two-phase region. Bubble Point Curve-the curve that separates the pure liquid (oil) phase from the two-phase (natural gas and oil) region.

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