Petroleum Development Oman (PDO) is planning two phase expansions to the Marmul polymer project, at an estimated cost of over $1bn to maintain and increase oil production at the field.

PDO is now close to approving the second phase of development, which will involve adding another 19 wells making use of the existing spare capacity at the feild’s phase 1 plant, according to Jamal al-Naamani, PDO’s lead engineer for the Marmul and Chemical enhanced oil recovery (EOR) cluster in the south directorate.

These will supplement the existing 27 wells from the original Marmul project about 200 kilometres northeast of Salalah.

Speaking at MEED’s Brownfield projects conference in Abu Dhabi on 10 December, Al-Naamani told delgates, a third phase is still in the conceptual phase, but could increase the number of wells at Marmul to more than 500 at a cost of more than $1bn, making it one of the largest polymer injection projects in the world.

Along with the construction of a 80,000-cubic-metre-a-day (cm/d) water plant and 17,500-cm/d polymer injection plant, the project was PDO’s first full-scale enhanced EOR scheme and began operations in 2010.

Discovered in 1956, the Marmul field is mature and produces extremely heavy, viscous crude oil, with most coming from the major reservoir, Al-Khlata. The technique works by mixing water with polymer to produce a viscous liquid that is effective at ‘sweeping’ the reservoir of oil. Water is separated from the oil after it emerges. The aim of the scheme was to arrest oil production declines at the field, which was producing between 60,000-70,000 barrels a day (b/d) and has also raised production by another 8,000 b/d.

PDO is the main exploration and production company in Oman, accounting for more than 70 per cent of the sultanate’s production of crude oil and most of its natural gas. The government of Oman owns a 60 per cent interest, while UK-Dutch Shell Group holds 34 per cent, France’s Total 4 per cent and Portugal’s Partex 2 per cent.

In November, Oman’s production of crude oil and condensates totalled 933,509 barrels b/d, a rise of 0.75 per cent compared with October 2012, according to the monthly report released by the Oil & Gas Ministry on 8 December.