Khurais HP Gas Compressor Swing Line Control Logic Modification Through Dynamic Simulation Modelling
Authors: Bajuaifer Hatem Abdullah , Khan Ashiff , Jansen Kevin , Al-Zahrani Abdullah Atiyeh , HE Yufeng 
Published: December 2021

Khurais central processing Facility is a hydrocarbon plant consists of 5 GOSPs with a stabilizer (i.e oil train), 3 gas plants and power plant with their associated utilities. Each oil train has one HP gas compressor to send the gas from oil trains to gas plant. These compressors is oversized and running each compressor alone results in excessive recycling and wasting energy. In 2018 Khurais introduced a new energy optimization initiative which is swing line that is a common header connects all HP compressors together with the objective of maximizing operating loads in each gas compressor. In doing so, the last compressor can be shut down for as long as the capacity of the other compressors is still adequate to accommodate the extra gas rate from the shutdown compressor.[1] (Refer to Figure 2) Although this approach resulted in maximizing energy efficiency of the facility it introduced a new challenge to the facility which is in case of any trip to a compressor connected to swing line all other connected compressors will trip. Recently Khurais introduce a new philosophy to shift the load from tripped compressors to other compressors through modifying swing line and compressors DCS control logics.

This paper covers the swing-line control logic modifications and enhancement followed by Saudi Aramco Khurais producing facility to overcome multiple compressor outages challenge.

This paper is aimed to:

Share the challenge of multiple compressors trips with swing line operations that occurs if one of the compressors connected to swing line is tripped resulting in 100% of gas flaring. Present dynamic simulation modelling results and new logic modifications implemented for compressor controls to avoid such multiple trips scenario. Present Compressor trips cases before and after implementing the control logic enhancements. Highlight how this approach enhanced compressor's reliability and helped Saudi Aramco to reduce its carbon footprint.

In this paper various dynamic simulation modelling graphs that showed the root cause for multiple compressor trips will be presented, evaluation of several control logic and their consequences. This topic will also cover the new proposed logic with zero investment to avoid multiple compressors trip scenario with operations of swing line. Details about behavior of compressor before and after the modification including the reaction of newly implemented control logic in flare control valves is included part of this paper.

After the implementation of this logic the following results have been realized:

No incident of multiple compressor trips happened due to proper functioning of logic. Eliminated 60-100 MMSCF/year of flaring due to multiple compressors trips scenario through having "quickest" handle to restoring flow to the swing line and stop flaring. Reducing carbon footprints due to flaring compared to old setup. Realized Recovered revenue worth approximately US$ 500,000/year

The novelty in this paper is describing an approach of gradual load shifting from a tripped compressor to other running compressors to avoid multiple compressors trips which can be utilized in any facility that has a common suction header connects all its compressors. Such logics can be implemented in-house with no modification in compressors or swing lines or other equipment.