As is often the way with highly complex infrastructure projects, Sasol’s Oryx gas-to-liquids (GTL) plant in Qatar was a long time in gestation. The South African company opened discussions with Qatar in 1996, but it was not until six years later, in 2003, that a lump-sum turnkey contract was finally signed for the construction of the facility.

Construction work on the plant – Qatar’s first commercial GTL facility – began in March the following year, yet was not without its teething problems. The construction phase was completed in 2006, but commissioning of the plant was delayed due to technical issues, and more specifically due to what Sasol officials described at the time as problems with a superheater on the unit. Full-scale operations eventually began in 2007.

Complex project

The plant also suffered from a difficult cost environment for construction work. “Rising EPC [engineering, procurement and construction] costs and resource shortages in construction, logistics and procurement were the real challenges in implementing the Oryx GTL project, a large and technically complex project,” said Italy’s Technip, the EPC contractor on the scheme.

More recently, though, operations have enjoyed a smoother ride. The plant is running close to its 32,400 barrel-a-day capacity, and sometimes a little over, and has run for more than two years without a lost-time outage.

Qatar’s venture into the GTL market was driven by a strategic decision to diversify away from its reliance on sales of liquefied natural gas, susceptible as they are to the variations of the global market. Although the volumes produced are relatively small, having GTL as part of its product mix gives the country the opportunity to take advantage of a global market in which oil is trading at a premium to gas.

The Oryx plant converts gas from the giant North Field into diesel, naphtha and liquefied petroleum gas (LPG). Sasol operates the plant in a joint venture with the government’s oil investment arm, Qatar Petroleum (QP). Sasol Synfuels International has a 49 per cent stake in the partnership, with QP holding the balance. Marketing is carried out in partnership with the US’ Chevron, under the Sasol Chevron brand.

The plant incorporates three core technology units: synthesis-gas production, licensed by Haldor Topsoe, which creates a synthesised mix of carbon monoxide and hydrogen, commonly known as syngas; Fischer-Tropsch synthesis, licensed by Sasol, which converts the syngas into liquid hydrocarbons; and product work-up, licensed by Chevron, to separate out the diesel, naphtha and LPG.

An array of ancillary processing facilities includes units for air separation, hydrogen production, heavy ends recovery, reaction water treatment and LPG clean-up. Technip carried out construction work in a two-phase process, comprising EPC work on the original plant and technological improvements following the start of operations.

Construction work on the 72-hectare project was of mammoth proportions. At the peak of construction, 4,500 people from 15 different countries were working on the site, with the labour force putting in a total of almost 30 million man hours. Prefabricated piping weighing more than 4,500 tonnes was used, while some construction equipment components weighed up to 2,000 tonnes.

Clean fuel

The diesel produced by the plant, which accounts for about four-fifths of total output, is much cleaner than that typically produced by oil refineries. Diesel from the Oryx plant has a sulphur content below – and usually significantly below – 5 parts per million (ppm), compared with that typically marketed in Europe, the target threshold for which is 10ppm.

The low sulphur content of the Oryx diesel makes it attractive as a blend stock to bring more sulphurous diesels below the threshold for sales in Europe. The bulk of the diesel is sold in northwest Europe, with a small amount sold to neighbouring countries in the Middle East.

The naphtha is also exported, mainly to South Asia and the Far East, where it is used as a cracker feed for the manufacture of downstream chemicals, while the plant’s LPG output is used to supply Qatar’s domestic market. For the time being, the plant does not produce kerosene – used to make aviation fuel – but should it wish to undertake the necessary modifications, Sasol has approval to produce the fuel for use in an aviation fuel mix up to 50 per cent.