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Carbon trap

controversy about the viability of using carbon dioxide for enhanced oil recovery was once again in the forefront recently with the starting of a Canadian project's new phase in which around 20 million tonnes of carbon dioxide would be injected into a reservoir located in Rejina for recovering oil.

With emission trading growing in importance, such methods are being explored as a way for reducing atmospheric carbon dioxide concentrations, as the gas injected gets stored underground. Storing carbon dioxide in oil formations is an attractive trading option, as costs of storing is partially offset by enhanced oil recovery.

As per the method, carbon dioxide is injected under pressure into oil-bearing rocks. If the pressure is high enough, carbon dioxide and oil get mixed. This reduces the viscosity of oil and makes it swell up. While some carbon dioxide does come up with oil, a large part remains underground and operations can be modified to increase the percentage that stays underground.

Many claim that it is a good and cost-effective way to reduce atmospheric levels of carbon dioxide. However there are some who do not agree. "There is no experience to date regarding the long-term safety of storing large volumes of carbon dioxide,' points out Michael Celia from the department of civil and environmental engineering, Princeton, usa. According to him, there is no guarantee that the carbon dioxide stored will not change sub-surface pressures resulting in earthquakes. It could also lead to an elevation of land above the depositories. Similarly there is no assurance that in the long run the stored carbon dioxide will not escape from the formations and contaminate drinking water and accumulate as gas in buildings. In addition to uncertain effects on the environment, it could also increase the risk of North dumping carbon dioxide in the South.

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