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Exxon Mobil Corp looks set to be on course to restart its 50,000 barrels-per-day (bpd) visbreaking complex at its mainland Singapore refinery by the end of this month, Reuters reports.

The U.S oil major has been carrying out maintenance at both its mainland and Jurong Island refineries since February, which has meant the company has been short of fuel oil to sell to the Singapore cargo market and is reported to have had a significant decrease in supplies to the Hong Kong bunker market. Availability of 380-centistoke (cst) has been particularly tight in Hong Kong since the end of March.

Visbreaking units at both Singapore refineries have been shut in stages, which in turn has had an impact on the production of fuel oil between early-March and April.

ExxonMobil's fuel oil supplies from its 309,000 bpd mainland refinery are drawn from its three visbreaking units, which crack residues left over from the crude distillation units into higher-value products.

The first of the mainland refinery's visbreakers was restarted at the end of March, whilst the second is expected to resume operations by the end of this week. The last unit is reportedly on course to restart by the end of this month.

When monthly production is running normally at 600,000-650,000 tonnes, Exxon reportedly sells around 50 percent to the Singapore bunker market and 40,000-80,000 tonnes to the Singapore cargo market. Approximately 200,000-250,000 tonnes are also sent to Hong Kong, however, the figure was said to be up to 40 percent lower in February and 10-15 percent less in March when the majority of ExxonMobil's available supplies were being used to cover marine fuel demand in Singapore.

ExxonMobil also uses output from its 300,000 barrels-per-day (bpd) Jurong refinery - also called the Pulau Ayer Chawan (PAC)- for sale in the Singapore marine fuels market and is amongst the top suppliers at the world's largest bunker port with a market share of approximately 8 percent.

According to data released by the Maritime and Port Authority (MPA), ExxonMobil was the second largest supplier in Singapore in 2008 behind BP Singapore Pte Ltd.

The Jurong Island facility operates two crude distillation units (CDUs) with a capacity of approximately 115,000 bpd and 185,000 bpd. The smaller one was shut for over two weeks in May 2007 after a fire.

Meanwhile, the mainland refinery also has two CDUs, one with a capacity of more than 200,000 bpd and the other with up to 100,000 bpd.