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SPM Oil and Gas Processing Series
SPM-3000 Gas Oil Separation Process

Click to view schematic display A Click to view schematic display B Click to view schematic display C Click to view schematic display D

Process Description

The Gas-Oil Separation Process separates gas from crude oil in a 4-stage separation process. The oil is sent to storage, and the recovered gas is recompressed in a 4-stage centrifugal compressor, and sent to treating.

Crude oil is produced from the wells in the first-stage separator. The gas leaving the first stage separator blends with the 4th stage compressor effluent, and is sent to treating.

The oil leaves the first-stage separator and enters the second-stage separator. The gas leaving the second stage separator blends with the gas from the 2nd stage compressor and the liquid from the 4th stage suction knock-out drum, and is cooled and sent to a knock-out drum before it is compressed in the 3rd stage compressor. The gas from the 3rd stage compressor is cooled and sent to a knockout drum before being compressed in the 4th stage compressor.

The oil leaving the second-stage separator flows into the third-stage separator. The gas leaving the third stage separator blends with the gas from the 1st stage compressor and is cooled and sent to a knockout drum before being compressed in the 2nd stage compressor.

The oil leaving the second stage separator flows through a crude oil cooler, which maintains the temperature of the oil entering the fourth stage separator. The gas leaving the first stage separator goes to the 1st stage knockout drum before being compressed in the 1st stage compressor. The cooled oil enters the fourth-stage separator, removes the water and then is sent on to storage. The quality of the oil to storage is maintained by controlling the fourth stage separator pressure.


Instrumentation

Crude oil is produced from the wells in the first-stage separator, D-101, at 1610 psig and 170 Degrees F. The gas leaving the separator is about 225 million standard cubic feet per day. The oil leaves the first-stage separator by level control, LIC-101, and enters the second-stage separator, D-201, at 330 psig and 150�F. The gas leaving the separator is about 60 million standard cubic feet per day.

The oil leaves the second-stage separator, by level control, LIC-201, and flows into the third-stage separator, D-301, flashing down to a pressure of 55 psig and a temperature of about 127�F. The gas leaving the separator is about 20 million standard cubic feet per day.

The oil leaves the third-stage separator under level control, LIC-301, and flows through crude oil cooler, E-402, which maintains the temperature of the oil at l00 �F by controller TIC-401. The cooled oil enters the fourth-stage separator, D-401, flashing down to a pressure of 8.5 psig. The fourth stage separator first removes the water by LIC-403, and then the oil is sent to storage by LIC-401. The flow rate of oil to storage is measured by FI-402, and by controlling the temperature, TIC-402, and pressure, PIC-402, on the fourth-stage separator, the quality of the oil to storage is maintained.

The gas coming from the fourth stage separator, D-401, about 6 million standard cubic feet per day is scrubbed in the 1st stage knockout drum, D-402, to knock out any liquids that might be entrained in the gas, before it goes to the first-stage compressor which compresses the gas from 8.5 psig up to 75 psig, raising the temperature from 100� F to 234� F. Anti-surge controller, FIC-401, controls a spillback to the compressor suction, which is cooled in E-401 by TIC-402. Gas comes out of first-stage compressor and passes through a pressure controller, PIC-402, which controls the pressure of the fourth-stage separator. The set point on this controller is used to vary the vapor pressure of the oil going to storage.

After the gas goes through the control valve of PIC-402, it is blended with the gas coming from the 3rd-stage separator, about 21 million standard cubic feet per day. The gas is cooled to 75 degrees F in E-301 controlled by TIC-302, and enters the 2nd Stage Knock-out drum D-302 before entering the 2nd stage compressor, which compresses the gas from 54 psig to 503 psig, raising the temperature to 304� F. Anti-surge controller, FIC-301, controls a spillback to the compressor suction. Gas comes out of 2nd stage compressor and passes through a pressure controller, PIC-302, which controls the pressure of the third stage separator.

After the gas goes through the control valve of PIC-302, the gas is blended with the gas coming from the second stage separator, about 60 million standard cubic feet per day, and liquid coming from the 4th stage knock-out drum D-102. The gas is cooled to 75 degrees F in E-201 controlled by TIC-202, and enters the 3rd Stage Knock-out drum D-202 before entering the 3rd stage compressor, which compresses the gas from 330 psig to 870 psig, raising the temperature to 219� F. Anti-surge controller, FIC-201, controls a spillback from the 4th stage compressor discharge to the 3rd stage compressor suction.

The gas leaving the 3rd stage compressor is then cooled to 75� F in E-201 controlled by TIC-102, and enters the 4th stage knock-out drum, D-102, before entering the 4th stage compressor, which compresses the gas from 850 psig to 1610 psig. The gas leaves the compressor and blends with the first stage separator gas, 225 million standard cubic feet per day, and passes through PIC-101, to gas treating.