Wellhead Compression – Minimum Suction Pressure

field compressor to trip-off prematurely. In this case, the field operators were reporting that they could not operate a compressor suction below 70 PSIG. Their experience had taught them the following:
1. They would set the compressor to operate in the tandum mode.
2. Over a period of a few days the wellhead pressure would diminish from 120 PSIG to 70 PSIG.
3. At 70 PSIG (as indicated by the flow chart pressure recorder) the unattended compressor would trip-off.

Figure 4-3 shows that this was not quite true. The cause and solution to this problem resided in the pressure setting of the threephase, low pressure separator. As this vessel was set to hold 65 PSIG, it followed that the high pressure separator could not drain whenever it’s pressure reached 65 PSIG. The liquid level in the high pressure separator would then rise and carry-over water to the field compressor. As engine fuel was being drawn from the compressor suction line, the water overflowing from the separator entered the engine and caused it to stall. The simple solution to this problem was to reduce the three-phase separator pressure from 65 PSIG to 30 PSIG.

Minimum compressor suction pressure is set by 3-phase separator

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