Non-renewable energy resources – oil, natural gas, coal and uranium – account for close to 90 % of the world total primary energy supply. Energy Agencies (e.g. IEA 2008) predict a further increase of the demand for all kinds of fuels. In the 1960es, oil has become the most important energy source with recently a share of 36 % on total primary energy supply. Although huge amounts of reserves and resources of conventional oil are still known, this kind of fuel will run into shortage in the predictable future. BGR expects the maximum of conventional oil production at around 2020. Yet, as several parameters for such a prognosis are uncertain, the “peak oil” year can move in both time directions. Due to the enormous importance of oil for the world economy we need to find alternatives. One of them could be natural gas.
Whereas natural gas reserves of 166 billion toe (toe = tons oil equivalent) (183 trillion m³) are grossly equivalent in amount to conventional oil reserves (164 billion t), gas resources of 188 billion toe (207 trillion m³) are much higher than conventional oil resources (82 billion t). Moreover, there are huge amounts of non-conventional gas resources i.e., in the order of 230 trillion toe for tight gas and coal bed methane (CBM) – roughly corresponding to all conventional and non-conventional oil resources – plus gas hydrates in the order of 1180 trillion toe (triple of the common oil reserves plus resources). However, production of non-conventional gas is more expensive and sensitive to ecological aspects. Still, non-conventional gas can play a role in the future energy supply, especially tight gas and CBM, possibly gas hydrates, too.
Can natural gas fill the predicted gap for oil? Consumption behaviour for oil and natural gas is showing significant differences. In OECD countries in 2006 petroleum products were mainly used in the transport sector (63 %) and in industry (25 %). Other sectors (residential, commerce & public and agriculture) are of secondary importance (12 %). Consumption of natural gas is dominated by other sectors: Main contributions go to heating of residential buildings (60 %) and to industry for process energy and heating of buildings (36 %). The transport sector, at present, accounts for only 3 %. Transformation of energy (generation of electricity) with natural gas is clearly higher than with oil (19 ExaJoule and 5 ExaJoule, respectively).
Looking at the potential of natural gas, we can conclude that natural gas can substitute oil in several sectors such as heating and industrial use. More challenging is the substitution in the transport sector due to the lower energy density and higher transport costs of gas. Despite the many options to use natural gas, it is a finite resource, like oil. In case of its exhaustive use we will, probably within the second half of this century, face the same situation as for oil today. For several decades natural gas could bridge the energy gap until future energy resources including renewables become available and affordable.