Over the last decade, the crude oil industry has been demanding more advanced produced water treatment systems. The focus is on optimizing produced water management from oil fields and enhancing the performance of existing water-handling facilities. Saudi Aramco, the world’s largest oil & gas company, has completed a performance test with GEA’s centrifuges and rated them as having excellent performance and reliability.
Better water quality while saving energy
Saudi Aramco conducted a field trial of a GEA disk stack centrifuge at one of its Gas Oil Separation Plants (GOSP) in 2019. The objective was to test the de-oiling and solid removal capabilities of the centrifuge from the produced water at fluctuating feed rates and inlet concentrations. The results of the test were published in a paper by The Society of Petroleum Engineers (SPE).
The test demonstrated for Saudi Aramco that the injection well could be used longer because its permeability was improved due to better water quality. In addition, the company can save energy when disposing of produced water because better permeability means lower pressure drops when pumping into the formation.
One byproduct of crude oil production is formation water, also known as produced water in the oil and gas industry. This is the largest sidestream of the production: In some areas, the water cut can be up to 80 to 90%. It’s critical for the whole industry and the environment that this byproduct is disposed of correctly. There are different methods of disposal. One of the most common is reinjection through disposal wells or production wells into the ground at very high pressure.
Disposal is highly regulated and requires high-quality treatment. At offshore sites, disposal directly into the sea is common practice, and many companies use GEA centrifuges. Centrifuges can also be used onshore when more demanding process requirements are fulfilled. It’s critical to get this right to meet environmental standards and ensure that wells are not clogged and formation permeability is not reduced, which can result in higher pressure drops during reinjection and, in the worst case, lower oil production.
GEA builds ready-to-connect, produced water treatment systems that operate with high centrifugal force (up to 10,000 g). These systems can treat produced water in a single process stage, or as an extension of existing technologies. They significantly optimize the process of treating formation water.
By 2019, Saudi Aramco had completed several projects to optimize its water-handling facilities and improve their performance. The company was focused on upgrading existing gravity separators by installing plate coalescers, but the oil droplets that were created were too small, which meant it took a long time for gravity to settle them. It also tried electrostatic separators, but their performance was not sufficient either.
By the last quarter of 2019, Saudi Aramco was convinced that the best equipment to use was centrifuges and decided to conduct a test with a disk stack centrifuge. Centrifuges provide immediate reaction to fluctuating inflow conditions because produced water is retained inside the centrifuge bowl for a shorter time.
Saudi Aramco wanted to test how GEA’s centrifuge technology would perform with their specific water and how it would meet the oil in water concentration of <50ppm (mg/L) in harsh conditions. GEA provided a process engineer and a test machine from the test machine fleet to carry out an on-site test at the customer’s premises. The test fulfilled all of Saudi Aramco’s requirements and safety standards.
The test was conducted at Saudi Aramco's Shedgum Gas Oil Separation Plant in December 2019.
The test results successfully demonstrated that GEA's centrifugal separator technology achieved and exceeded the expected separation results of <50 ppm oil in water, reducing the content of oil and solids in Saudi Aramco’s stream of produced water by an average of 10 ppm, no matter what the feed composition.
Saudi Aramco has said the performance, reliability, low energy consumption and small footprint of the GEA machines was outstanding.
With the results and data from the tests, Saudi Aramco will be able to scale up the use of centrifuges precisely, for instance at a large-scale production plant. It will also be able to predict machine performance and flow rates using the equivalent clarification area figure of a single centrifuge.
As a result, the company will be able to make estimates for machine design, plant size, performance and CAPEX / OPEX. Based on data from the test, we know that the company could purify 15,000 BPD (100m³/h) of this specific water using one of GEA's largest centrifuges. GEA can supply produced water treatment systems that are nitrogen-purged, hydro-hermetically oxygen sealed, fully automated and ATEX / IECEx- compliant. They are made of highly corrosion and erosion-resistant materials, such as super duplex.
Saudi Aramco can achieve higher flow rates as well by installing multiple centrifuges in parallel. The tests showed that an uptime rate of > 99% per year is possible. The company saw how it can use this machine at substantially low lifecycle costs to achieve an oil-in-water content of less than 25ppm, with simultaneous separation of residue particles. The results showed that the centrifugal separator provides high efficiency de-oiling (>90% for high oil-in-water concentrations) and handles high inlet oil-in-water feed concentrations.