With one of the most complex geologies in the region, Oman is increasingly turning to the use of enhanced oil recovery (EOR) techniques to raise oil production.

Primary extraction, in which oil flows to surface because of the natural pressure of the reservoir, can typically recover 5 to 20 per cent of the oil in place. Secondary techniques, using water flooding or gas injection to maintain pressure, can also allow the recovery of 10 to 20 per cent. Using EOR, between 30 to 60 per cent more of the reservoir’s original oil can be extracted.

These techniques include the injection of natural gas, carbon dioxide or nitrogen, and thermal recovery, employing high pressure steam injection, which is typically favoured for the displacement of heavy oils. Chemical recovery can also be used. This involves injection of surfactants, polymers or alkalis such as caustic foam to reduce the surface tension which traps oil.  

By 2018, state-run Petroleum Development Oman (PDO) expects primary extraction methods to represent only 39 per cent of production, down from 47 per cent currently and almost 70 per cent in 2000. The use of secondary techniques is also falling, down to 25 per cent by 2018. EOR, however, will contribute as much as 36 per cent of total production by then, from only 16 per cent currently.

According to UK engineering firm Mott Macdonald, PDO is the only company in the world currently implementing multiple large-scale EOR projects simultaneously. The company is planning nearly $10bn-worth of EOR project investments over the next 10 years.

Its EOR portfolio is currently spread across more than four fields. This includes polymer injection at the Marmul field, which is expected to produce 8,000 barrels a day (b/d) when completed.

It is currently commissioning the Qarn Alam steam injection project, costing an estimated $1.2bn, one of the largest full-field EOR projects in the world. After an initial ramp up of production for an estimated three years, the expected plateau production rate is expected to reach 60,000 b/d and 1.2 million cubic feet a day (cf/d) of gas. The project also included the construction of s 24,000 tonne-a-day water (t/d) treatment facility and 18,000-t/d steam injection plant.

Gas injection is being used at the Harweel field, and steam-based EOR at Amal East and West fields.

The US’ Occidental took over PDO’s development of the Mukhaizna field in 2005, when production had fallen to 10,000 b/d from 16,000 b/d. Debottlenecking and pilot stream injection schemes have ramped production to 18,000 b/d.

Full EOR facilities have been established, totalling some $800m, allowing the company to produce 75,000 b/d and progress towards its target of 150,000 b/d by 2012.

Oman’s oil production currently stands at 816,000 b/d, up 14 per cent on the 714,300 b/d produced before the introduction of EOR techniques.

Mott Macdonald is involved in five EOR schemes, spread across eight fields with a total value of $2.325bn which are expected to add some 253,000 b/d of production by the end of the decade. The country is planning to implement another five major EOR projects before 2016 worth an estimated $4bn.