Phase Behavior Characteristics of Rich Gases and Their Engineering Significances

For the rich gas transmission schemes, extraction of NGL from the natural gas is not required in the oilfield or gas condensate field, so the gas treatment processes in the field is simplified and the expense from the storage and transportation of NGL is saved. Rich gas can be transported in single phase under conven- tional pressure, dense phase, or two-phase. The phase envelopes of typical rich gases are calculated to investigate the effect of the composition of rich gases on the characteristics of phase behavior. Only the rich gas with low contents of C₃ and C₄, and with the strict condensate removal, could go a long distance in single phase under conventional pressure. The dense phase alternative may have a requirement for moderate removal of condensate from the gas for the sake of cricondenbar. In most cases, the hydrocarbon dew point is not specified for the two-phase transmission of rich gas, but condensate removal could lower the volume content of liquid accumulated in the pipeline. Dense phase or two-phase alternative is a common selection for the rich gas.