De-Salting Train Transformers Retrofitting and Optimization Study to Achieve Flexibility and Efficiency in Saudi Aramco

Abstract

This paper covers and evaluates a retrofit work for desalting trains grids in Saudi Aramco Khurais facility to accommodate water cut increases due to field maturity. The main objective of this retrofit work is to accommodate the increase in water cut (emulsified and free water) while enhancing the de-salting process with minimum modification scope and cost effective approach. This Paper is intended to: Presents the retrofit basis and compare old and new grids design. Presents the results of this optimization study along graphical representations. Highlights how this initiative increased the desalting trains efficiency and redundancy. The basic concept of the retrofit work is to change the grids in electrostatic separation vessels from the conventional tapered configuration to straight configuration. The original configuration was tapered configuration that is intended to maximize separation and balance the load on all transformers however the limitations of this configuration is in case of one grid shorted all other transformers will be shorted. Despite the available transformers capacity, however as the water cut increases the chances of water carry-over increases as well as emulsions which results in multiple outages of de-salting trains. Straightening the grids will help avoiding total outages of the transformer, so in case of one grid shorted, other two grids will be running with a higher load which provides redundancy, reliability and guaranteeing the quality targets. This modifications were evaluated from safety, process, electrical and cost life cycle point of view and assessed post retrofitting for 1 year against there pre-defined success majors that includes: Outage hours of dehydrator and/ or de-salter (Target less than 5 hours per quarter). Demulsifer chemical consumptions (Target reduction by 10% or more annually) Quality specification (Target maintaining BS&W and Salts within crude specifications of 0.2% and 10 PTB respectively even in case of 1 or 2 transformers shorted. This modifications succeeded in achieving the predefined targets in addition to a cost saving equivalent to US$ 120,000 due to demulsifer injection reductions (i.e Regular and emergency dosage). Figure 1 shows the change in grids configurations before and after retrofit work