There is a close connection between gas and oil and it is the case that between 15% - 20% of world oil is actually based in some way on gas. Due to the imminence of peak oil, there has been a shift away from conventional oil production toward such lighter hydrocarbon fuels described as NGL (natural gas liquids) and condensates, which are liquids that are condensed out from raw natural gas, while the gas-component is most often re-injected in order to maintain adequate pressure within the reservoir, or simply vented away or "flared-off". It is a familiar sight throughout the history of the oil-industry to have burning highly smoky gas flares that are actually contaminated with large amounts of liquid hydrocarbons (oil) and various minerals and metals too, most of them highly poisonous in nature. When the gas is simply vented it is invisible to the naked eye, but potentially nonetheless a threat in terms of climate change, dumping methane into the atmosphere. Methane is a particularly potent greenhouse gas, with around 100 times the "global warming" capacity of CO2. It is often quoted that methane is about 20x as bad as CO2 in this respect, but that refers only to the situation averaged over 100 years, during which course some of the methane is broken-down by being oxidised to CO2 in the troposphere. After 300 years, there will be practically none of the initial methane remaining. In reality, if equal volumes of methane and CO2 were released into the atmosphere, the heating effect, the "instantaneous radiative forcing factor" as it is known, is nearer 110 [I will supply the math(s) behind this conclusion if anybody asks me]. Worryingly, about 9% of world gas is pumped straight into the sky, in other words is wasted, without finding any use as a fuel.
Undoubtedly, peak oil comes before peak gas - and may have already done so, and there are numerous estimates for the times when either will arrive. It is not a simple stepwise advance of one over another though, due to their interrelated aspects, both physical (chemical) and economic. Increasingly, oil is made from gas as a raw material, from "hot greasy gas" as Andrew McKillop has described it, and which is formed at depths of 3 - 4 kilometers underground. In "extreme depth offshore" regions like Angola and the deep Gulf of Mexico, that "ground" may be seabed that is itself 3 - 4 km underwater. Using the classical wooden "derrick" of the oil-gusher days, for "conventional" production of oil, there would certainly have been some gas in the "oil-stream", but nothing to compare with present production of "unconventional" oil, which is reckoned at the equivalent of one oil barrel equivalent of gas produced and re-injected, vented or flared, for every 8 barrels of oil that are condensed out of "greasy gas", as a world average. As wells become "older" that ratio is much higher, and more determined strategies are employed to recover more oil from the "greasy" oil-gas stream, to the extent that in the US, "conventional" oil production amounts to just about one quarter of the total oil produced there, which is around 1.5 million barrels a day from near to 6 million barrels altogether. Since the US gets through around 22 million barrels daily in total, rough reckoning indicates that it must now import almost 3/4 of its oil. Now that figure is alarming, and we can draw our own conclusions as to what that will mean on the world stage.
It has been assumed that Russian gas is in practically unlimited supply, as was thought of the Saudi oil fields about two decades ago. We now know this is not true. Neither does it appear that the Russian Gazprom can supply Europe with sufficient of its gas requirements into the future. Despite claims of huge gas resources, it seems that in reality, falling supplies from the three critical ("biggest") west-Siberian gasfields are unlikely to be able to provide even in the short-term for Russia's own domestic, CIS and European customers. Part of the problem is the need for a massive investment programme, to extract more gas and to do it more efficiently, and in the absence of such a capital cash-injection it is only at a push that the period 2009-2015 will not witness significant gas-shortages across the whole of Europe and the former Soviet Union - a massive total region with somewhat over 1 billion people. Put bluntly, "Peak Gas" is likely to strike in 2009... in a couple of years from now.
Peak oil is grudgingly becoming acknowledged and accepted, although the apocalyptic consequences of simply sitting by and letting the consequences of it happen are not routinely broadcast. Possibly there is a plan to avert mass-panic. The price of gas and that of oil will become inextricably linked and probably economic drivers - high cost - will kick-in and act as a brake on how much of these commodities is used. There will be little comfort found in this, however, especially in the midst of a very cold winter.
Andrew McKillop, "Peak Oil to Peak Gas is a short ride". http://www.energybulletin.net/print.php?id=23462