This article was first published on Geoexpro.
Vast amounts of shale gas promise a new energy future for North America, perhaps even for Europe. However, recent developments indicate that whilst the gas is undoubtedly there, the transformation of energy markets is unlikely to happen overnight – a long view is necessary.
Global gas reserves
The 2010 BP Statistical Review of World Energy noted that global proved reserves of natural gas grew by 2.21 Tcm (78 Tcf) in 2009, driven by increases in Russia, Venezuela and Saudi Arabia. The global R/P ratio increased to 62.8 years, representing the length of time that those remaining reserves would last if production were to continue at the previous year's rate.
Proved reserves of natural gas are those that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and operating conditions.
So even under these quite conservative assumptions, global gas reserves are considerable. Global gas resources, dominated by all manner of unconventional gas sources that are yet to be proven commercial, are vastly more. Unconventional gas includes Tight Gas, Coal Bed Methane, Shale Gas and – potentially – Gas Hydrates.
Gas reserves are dominated by the Middle East, Europe and Eurasia (i.e. Russia) and Asia Pacific. In contrast, gas resources (excluding gas hydrates) are dominated by North America and then the FSU. Shale gas is the dominant contributor in North America, China, Latin America, the Middle East/North Africa and the rest of the world, which excludes the former regions and the FSU and Western Europe (Stevens, 2010).
Science and Technology Behind Shale Gas
The fundamental idea behind the exploration and exploitation of shale gas is that in some cases, rich oil-prone source rocks buried at the centre of a basin will have passed into the gas generation ‘window’ and that most of the gas, rather than being expelled and subsequently migrating into conventional traps, will be retained trapped in the source rock itself. This basin-centred saturation concept can be applied to shale oil as well, where a source rock has entered into and then remained in the oil generation ‘window’. Some pundits argue that up to 75% of the generated hydrocarbons remains in the source rock.
These plays involve considerable risk and it seems that as many as 75% of wells are non-commercial at current North American gas…
