With supply struggling to meet surging demand as economic recovery accelerates, the Paris-based IEA expects average oil prices to increase in real terms to $87 (£52) per barrel by 2015, $100 by 2020 and $115 (or $190 in nominal terms) by 2030. Oil is currently trading at around $80 per barrel, up from just $32 last December.

This is a prognosis for oil prices with which Steve Thornber, head of global energy research at Threadneedle, concurs.

"Given the global supply and demand dynamics, we believe energy prices will move upwards over the medium and long term," he says.

Driving this global demand will be the future rapid growth of energy demand in fast-developing economies such as India and China, where per capita energy use is currently a fraction of that in economically advanced countries. On the supply side, the major oil companies are finding it ever more difficult to replace their reserves and are being forced to explore in increasingly hostile environments, says Mr Thornber.

"The impact of rising oil prices on economic growth will depend upon the trajectory of oil prices. If they rise gradually, stock markets and economies will be able to adjust. But if there is a sharp jump – such as that which occurred in 2008 – it could prove a shock to both markets and economies," Mr Thornber warns.

So what is the best way for investors to exploit the long-term trend of rising energy prices?

Oliver Burns, private client fund manager at Jupiter Asset Management, says clients have numerous means at their disposal, depending on their objectives and attitude to risk.

Investors can, for example, opt for broad equity funds that invest in regions with a high level of exposure to changes in the oil price, or in natural resource funds "where you are relying on the skills of a fund manager to select the right time to invest in the sector and the right companies to invest in".

There are also energy funds that will provide a purer play on companies in the sector.

"These funds won’t track the oil price as there are numerous drivers for share prices in oil companies outside of the oil price, such as M&A activity," argues Mr Burns, adding that investors can also buy shares in individual oil companies.

Conversely, investing in the 'supermajors' is not the answer, according to Mr Thornber.

"Bizarrely, the likes of BP or Royal Dutch Shell are not that sensitive to oil prices. They’re not really increasing production or replacing their reserves, and they have other businesses, which are holding back their overall progress," he says.

"At Threadneedle, we are thus focusing upon companies that are actively drilling and finding new resources. We have targeted exploration and development companies, such as Tullow Oil, and the likes of BG, the latter of which has announced large finds offshore of Brazil."

Mr Thornber believes that "national champions" will be another beneficiary of rising oil prices. Countries such as Russia with large oil reserves increasingly wish to exploit their resources through domestically owned companies – another problem facing the supermajors.

Tim Guinness, who manages the Global Energy fund at Guinness Asset Management, also advocates a focus on some national champions, such as PetroChina, as well as on medium-sized, independent exploration and development companies. But he does not exclude the oil majors from the investment landscape, since these will "benefit from rising oil prices over the long run and they are very cheap".

Petrobras is an example of a national champion favoured by fund managers. Brazil wants to control more of its reserves in the future, and Petrobras thus receives preferential access to resources. In addition the company has recently made some major oil discoveries – another bonus for investors. Yet value for money remains key.

"You have to keep an eye on valuations," warns Mr Guinness. "Petrobras was relatively cheap but it’s pretty fully valued now."

An alternative way to play the forecasted rise in oil prices is to focus on service companies – a path that Threadneedle is pursuing.

"Oil firms are outsourcing and subcontracting more and more of their activities to specialist service companies, as projects become increasingly complex," says Mr Thornber. "We are thus looking at drilling companies, particularly deep-water drillers."

The ocean depths are indeed the latest frontier of oil exploration. Consequently, there is huge demand for rigs that can drill in two kilometres of water, with the wells located up to a further 10 kilometres below the seabed.

Investing in a country-specific fund such as Brazil or Russia could be a further option for those seeking rewards from higher energy prices. The latter should, in principle, benefit these countries’ wider economies; moreover, energy tends to form a large part of the benchmark, so the local stock market and the funds that invest in these countries should also perform well.

Yet Tim Guinness believes that country-specific funds are a "hopeless way" of targeting rising oil prices. This is because investors are exposed not just to energy, since the fund will also be investing in banks, industrials and other areas. "You are much better off investing in funds that are focused on the energy sector," he asserts.

As Mr Thornber points out, an investor is also reliant upon the fund manager in terms of attitude to energy: "The manager may have a positive view and thus hold a significant weighting in the sector, but you can’t take this for granted. You also have to hope they choose the right companies."

Exchange traded funds (ETFs) are a low-cost means of gaining exposure to the whole energy sector. They do not target specific companies but simply mirror the performance of the sector or track a particular index.

By contrast, an actively managed fund can target individual companies such as Tullow or BG, which have the potential to outperform the supermajors that dominate the energy index.

"Certainly, anyone investing in ETFs over the past year would have seen little benefit – the sector as a whole has more or less tracked the world index," Mr Thornber adds.

In terms of evidence, Guinness Asset Management has just completed a study showing that actively managed funds beat the ETFs that track energy equities over a five-year period.

"The outperformance of actively managed funds is partly explained by the fact that the ETFs track indices that are too overweight in the oil majors," Mr Guinness says.

In conclusion, investors can gain exposure to the anticipated long-term rise in the oil price in a number of ways. As with all potential investments, those seeking to maximise their returns need to research thoroughly the funds, the options and the wide range of companies in the sector. Ascertaining a fund manager’s views on energy prices, and which sectors and companies they think will outperform, is as good a place as any to start.

Anthony Beachey is a freelance journalist

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