Enhancing opportunities: Challenging terrain requires advanced extraction techniques

The nature of Oman’s geology and the locations of its proven crude oil reserves mean that the sultanate has had to become a pioneer in the area of enhanced oil recovery (EOR) technology. EOR includes a range of techniques for extracting oil from geologically difficult reservoirs. As Oman’s more easily accessible reserves deplete over the coming years, advanced techniques will become increasingly important, and indeed some of the region’s most innovative and largest EOR projects have already been launched in the sultanate.

Growth Area

Oman’s geology has long presented a challenge for oil engineers. Much of its reserves are hard to access, with reservoirs in small pockets in complex rock formations deep underground. While EOR remains a marginal concern at the moment, its importance is expected to grow rapidly over the next decade.

An October 2013 report by Petroleum Development Oman (PDO) forecast that oil extracted using EOR techniques would account for 16% of Oman’s output by 2016, up from 3% in 2013, and rising to 22% by 2021. The development of EOR will boost demand for suppliers and service companies operating in the segment, and Oman will need to ensure it has very specific technical expertise to implement its EOR projects.

PDO’s first full scale EOR project was implemented in October 2010 at its Marmul field in the south of the country. In August 2013, PDO announced that it was implementing six different EOR technologies – including a full spectrum of thermal, chemical and miscible recovery – in efforts to find the best combination of processes to optimise production. PDO’s managing director, Raoul Restucci, said that the company was testing both established and new EOR techniques for their suitability in Omani conditions.

Among the EOR projects are a thermally assisted gas oil gravity drainage recovery mechanism at PDO’s Qarn Alam field, and a miscible gas injection system with steam injection and polymer flooding at Harweel.

Gas Injection

PDO currently uses three main types of EOR – miscible gas injection, thermal recovery and chemical recovery. Miscible gas injection involves injecting a gas into the reservoir into which crude oil can dissolve, making it easier to move through the rock and out of production wells. The Harweel project using this technology has some of the world’s oldest hydrocarbons deposits. The EOR plant has wells that are 14.5 km deep and uses high-pressure inlet separators to divide the oil from the solvent gas. The oil is then washed to remove salt, stabilised and exported. The gas is then either injected back into the well at 550-bar pressure (that is, 550 times atmospheric pressure) or sweetened and exported for commercial use.

As PDO notes, this process requires the production and injection wells to be very carefully located, and extensive mapping and analysis of where the gas in which the oil is dissolved will move through the rock formations. The extremely high pressure of the gas demands that the facilities for handling it be very robust, particularly given the dangers of toxicity.

Thermal

The Qarn Alam project uses thermal EOR, specifically thermally assisted gas-oil gravity drainage (TAGOGD). Thermal extraction works on the basis of heating the heavy, thick oil to make it lighter and less viscous, and thus easier to move and extract. TAGOGD, which was used for the first time anywhere in the world at Qarn Alam in 2010, is a complex method that involves heating the reservoir rock by injecting steam into the fractures, with the result that the oil moves more easily into producing wells at the bottom of the reservoir. TAGOGD is best used in highly fractured reservoirs.

PDO’s Amal West field uses another form of thermal EOR, steamflooding, which involves injection of steam into permeable but un-fractured reservoirs to form condensed water, which releases latent heat to make the oil flow more easily. It also helps lighter hydrocarbons mix with the oil, thinning it further.

At the Amal East field, PDO uses cyclic steam injection, which again involves pumping steam into the reservoir. In this case, the well is shut off for several days to allow the steam to heat the oil and condense into water, which is then extracted, mixed with the oil, through the injection well.

Finally, a fourth variety of thermal EOR is in-situ combustion, which involves igniting some of the oil in the well to heat the oil around it to make it less viscous while also creating gases and steam that put pressure on the crude and push it towards the production well. In-situ combustion tends to be used only in reservoirs with a high degree of permeability, and even then sparingly, as the process is relatively dangerous and complex.

Chemical

At its Marmul field, PDO has developed chemical EOR, using polymers as a thickening agent in water, making it more viscous, and injecting the resulting liquid into the reservoir to push out heavy crude oil. The Marmul field was first identified in 1956, and originally it was thought that only 10-20% of the oil would be extractable using conventional methods as the reserves are so heavy. The first polymer pilots were tested here in the late 1980s, which raised estimates on how much oil could be recovered to around 30%. However, plans to develop the field using chemical EOR were shelved as other fields in Oman offered resources that were cheaper to extract. But with more accessible reservoirs depleting, and oil prices high enough to justify the extra unit cost of EOR, polymer extraction was launched at Marmur in 2010.

“Using conventional recovery methods allows for a small fraction of resources to be extracted from the country’s oil fields,” Vinod Shah, managing director for Oman at Mott MacDonald, a consultancy, told OBG. “Thus the sultanate has become a fantastic laboratory for testing and achieving best results from steam, polymer and carbon dioxide extraction techniques.”

Solar

In May 2013, PDO and GlassPoint Solar, a California-based company specialising in solar EOR, announced the commissioning of the world’s largest solar-driven EOR project at the Amal West field in southern Oman. The 7-MW project delivers 50 tonnes of steam a day to existing heavy oil EOR operations at Amal West without producing damaging emissions. It uses GlassPoint’s enclosed trough technology, which deploys mirrors rather than solar panels to concentrate the sun’s rays on water tubes. The system operates within a glasshouse not dissimilar to those used in agriculture. The benefits of the technology include lower capital costs than conventional solar cells – equivalent to those of using gas, according to GlassPoint – and the protection afforded by the glasshouse, which makes the sites easier to maintain.

The Amal West project will help determine the potential of solar-powered EOR in Oman. According to Syham Bentouati, head of new technology implementation at PDO, it is being viewed as “a performance and operational baseline for future solar steam generation projects in Oman, providing us with valuable information for planning potential future large-scale solar steam projects”. The project’s pilot stage is due to end in January 2014, after which further decisions will be made about rolling out other solar EOR facilities.

Given the sultanate’s year-round sunshine, there are high hopes for the technology. GlassPoint says that its technology can reduce gas consumption at EOR facilities by as much as 80%. This could potentially be a boon for the country as a whole as well, freeing up more gas either for domestic supply or, potentially, export.

Global Centre

While it might be a stretch to call Oman’s difficult geology a blessing in disguise, there is little doubt that the country has become a leader in deploying EOR, to the benefit of local production and indeed the international players in the country. “Oman has the potential to be a technological leader in the region,” Dave Campbell, general manager of BP Oman, told OBG. “As the sultanate continues to diversify due to its declining resource base, EOR and other techniques will prepare Oman for the future. “ It should be said that while companies working in Oman use EOR techniques that are barely known, let alone deployed, elsewhere, the technology is not usually developed in Oman itself, but imported. However, Oman is developing substantial domestic expertise at using enhanced technology and the knowledge transfer to Omanis and local companies could help them gain work on EOR projects across the world in the future. EOR is only likely to become more important worldwide as other countries find their more accessible oil reserves depleting and need to access reserves that are as geologically challenging as Oman’s.

EOR may account for a relatively small proportion of Oman’s total oil production at present, but the practice is rapidly growing. “The Oman oil industry is at the forefront for new initiatives and technologies. It is a strong point of national pride to be able to provide technical solutions and expertise in the global oil and gas sector,” Usama Barwani, the director at MB Petroleum Services, told OBG. Thanks to the efforts of PDO and its international partners, Oman has stayed ahead of the game, and the raft of EOR pilots that have been launched in recent years will help test a range of techniques for their suitability in the sultanate. These projects are laying the foundations for a future in which EOR is an essential part of the sultanate’s economy.