Natural gas produced from underground reservoir is saturated with water and hydrocarbon vapor. The moisture content in natural gas steream is dependent of temperature and pressure, the higher temperature and the lower pressure, the higher moisture content. As the wellhead pressure continue to declline, the water content of produced gas will continue to rise.
The dehydration process at Cluster 4 consists of two stages, namely Low Pressure (LP) Dehydration System and High Pressure (HP) Dehydration System which has different operating pressure and temperature. Currently, the performance of LP Dehydration and HP Dehydration System is under-perform that can be seen from the difference in the gas outlet chiller temperature between design condition and actual condition. Based on the root cause anaylsis, there are some equipment suspected do not work properly, such as pressure control valve in HP Chiller and Propane Compressur Anti-surge Controller (CCC).
To maintain the desire moisture content of the gas at 36 lbs of water per MMSCF of gas, the suspected equipment that do not work properly need to be repaired or upgraded. After the dehydration system work properly, the operating temperature of the Porpane Chiller need to be reduced accordingly to maintain the desired water content. For the high pressure gas after booster compressor unit at pressure 335 psig, the chiller outlet temperature neet to be maintained at 55°F to prevent hydrates formation.