Doha has yet to deploy enhanced oil recovery techniques (EOR) for its fields. Efforts to increase crude reserves are currently centred on waterflooding and continuous gas lift methods for offshore production. The country’s oil fields have not depleted to the extent that other methods are necessary.

Over the next decade the market for EOR techniques could be ripe for growth. Waterflooding is considered a secondary production method.

EOR techniques such as injection of miscible gas, for example carbon dioxide, hold promise and make economic sense in a country with high emission rates.

 The key players working to increase oil reserves in Qatar are state-backed Qatar Petroleum (QP) and Danish company Maersk, which produces at the Al-Shaheen oil field.

Increasing oil production

Onshore, QP is enhancing production with waterflooding at the Dukhan oil field, where production started in 1947. At present, output amounts to 335,000 barrels a day (b/d), with injected water pushing the oil to the production wells.

Offshore, the Bul Hanine and Mayday Mahzam fields, are pressurised by continuous gas lift, with gas replacing the produced crude.

Maersk discovered oil in the 780 million b/d Al-Shaheen field in 1992 and started production two years later.

The international oil company (IOC) constructed the world’s longest horizontal wells to develop the thinly spread reservoir, located about 70 kilometres northeast of the Qatari peninsula.

The length of horizontal development has been gradually increased. In 2008, the limit was extended beyond 40,000 feet when a production well in the Kharaib B section was drilled to a world-record depth of 40,320 feet.

Maersk understands the complexities of the Al-Shaheen field. The company is investing $100m into a research facility at the Qatar Science and Technology Park. It has also entered into a partnership with Dutch consultancy and technology developer TNO to develop production enhancing technologies.

“With Maersk, what we are looking at is how to apply EOR for extremely long horizontal wells,” says Anton Leemhuis, managing director at TNO.

The basis for improving the production process is better monitoring, modelling and the effective interpretation of the data collected. This approach is not unique to Qatar and is known as the smart field, or smart well concept. For Maersk, the emphasis will be on optimising the waterflood of the Al-Shaheen field.

The geological properties of the field have thrown up some formidable challenges for Maersk. The field comprises carbonate rock and more permeable sandstone rock.

In the carbonate sections, in particular, there is a risk of the injected water flowing directly from the injector well to the producer well, without pushing the oil to the surface. This is known as inter-well short circuiting that results from the uneven flow of water.

With Maersk, what we are looking at is how to apply EOR for extremely long horizontal wells

Anton Leemhuis, TNO

“It is an art to deal with the various inconsistencies, some of the rocks are very porous, some of them come in cracks, so water will flow through it and before you know it you are only producing water, as water takes the path of least resistance,” says Leemhuis.

“There are a lot of heterogeneities in characteristics of reservoirs and even in sections of a reservoir that make it very difficult to get an efficient flow of water.”

To be able to control the various zones in a well, Leemhuis stresses the importance of effective monitoring.

“The only way to do that is to get a grip on the production process, so to better understand what is really happening two-three kilometres below your feet.”

Latest oil recovery techniques

Waterfloods could also be improved by other means. “Qatar’s oil reservoirs may benefit from designer water floods,” says Christiaan van der Harst, regional resource volume manager at UK/Dutch Shell for the Middle East and North Africa region.

“Designer water works by changing the salinity of the injected water, so modifying the ‘wettability’ of the rock.”

Chemical enhanced oil recovery also holds promise for a number of Qatar’s oil reservoirs. Chemical EOR relies on the injection of polymers to enhance the flow of oil through the pores in the reservoir.

Beyond these techniques, producers in Qatar should look to miscible gas injection. Miscible gas changes the viscosity of the oil, allowing it to flow more easily.

“[They] could consider the application of miscible gas injection, especially if the miscible gas, for example carbon dioxide, can be extracted from power plants or industrial projects,” says Van der Harst.

Enhancing oil recovery with liquefied carbon emissions or carbon dioxide has been practiced in the US for some time. Similar projects are now under way in Abu Dhabi and Saudi Arabia.

Apart from the environmental benefits of storing the pollutant underground, carbon dioxide lends itself well to EOR as its low viscosity improves the flow of oil significantly.

Carbon emissions

Qatar produces among the highest amounts of carbon emissions per capita in the world. This, in combination with depleting oil fields, makes carbon dioxide EOR an attractive option for oil producers in the country.

“At some point waterflooding will only give you so much, then carbon dioxide EOR becomes an option,” says Leemhius.

“EOR is one of the few business cases of carbon dioxide management that has been proven to be economically viable in some cases,” adds Leemhius.

“The question is whether that also applies to Qatar. But the simple fact that you have a lot of carbon dioxide available and you are producing oil fields, it is a pretty logical conclusion to start looking.”

There are some questions over carbon dioxide injection into oil fields in Qatar and other GCC countries such as the UAE. Hydrocarbons produced in those countries contain a high level of carbon and it is unclear how this affects the carbonate rock in a reservoir. The same advances in oil field monitoring and control would have to be applied to get optimum results from carbon dioxide EOR.

Gas recovery in Qatar

Qatar is the world’s largest producer of liquefied natural gas (LNG), producing 77 million tonnes a year. With the bulk of hydrocarbon activity on the gas side, the question is whether the production of gas should be enhanced in future.

“Enhanced gas recovery could be considered in Qatar, although the feasibility has not yet been investigated,” says Van der Harst. “Introduction of non-hydrocarbon gases into a gas reservoir needs to be managed and monitored very closely. A breakthrough of non-hydrocarbon gas will affect production rates.”

With oil production still increasing year-on-year and 2011 being the first year of full production from its newly expanded LNG infrastructure, time is on Qatar’s side. This will enable it to study and perfect the techniques required long before they need to be deployed.