Applying Split-Range Pressure Control as a way for Maintaining Production

Abstract

Jambi Merang's Sungai Kenawang Plant (SK) is central gas processing facilities consists of processing systems including separation, condensate stabilizer, mercury removal, CO2 removal, dehydration, condensate recovery, metering and utility systems including air instrument, heating medium, flare and fuel gas.

At normal operation, fuel gas consumption is taken from suction sales compressor (350 psig, 105°F, CO2 4.5%, H2O 5 ppm, Heating Value 1140 Btu/scf, Wobbe Index 1360 Btu/scf). Fuel gas is reduced to 247 psig using Pressure Control Valve (PV) and then distributed to heater/thermal oxidizer, blanketing, power generation and turbine compressor.

Based on the design, a 6" PV is installed to deliver fuel fuel as needed to 7.6 MMscfd. Whereas during operation, the amount of fuel gas that is being flowed and required is only 4 MMscfd. This condition, in experience caused PV to become often unstable in controlling the pressure and also causing the PV to often close and finallly create an unplanned shutdown.

In order to improve controlability of PV and increase availability of Fuel Gas System, modifications have been made including changing the number and size of PV to be 2 pieces 4" and modifying the PID controller into a split-range, in which the output of a controller is split to two valves. Two PVs is installed parallel with different setting i.e. 245 psig and 250 psig respectively.

Currently, no unplanned shutdown occurs by applying a split-range control scheme.

This paper describes an overview of success in applying split-range pressure control as a way to maintain production. Preparation step, study and implementation are also discussed.