• Overview
  
  
• Overview: Conventional Oil
  
  
• Conventional Oil: Simple Estimate
  
  
• Conventional Oil: More Realistic Estimate
  
  
• Overview: Natural Gas
  
  
• Natural Gas: Simple Estimate
  
  
• Overview: Coal
  
  
• Coal: Simple Estimate
  
  

During 2001, natural gas provided 23% of the energy that is “consumed” [1,2] by all the people of the world. The International Energy Outlook 2004 (IEO 2004), published by the United States Department of Energy (USDoE), contains a projection that, in 2025, natural gas will provide 25% of the energy consumed globally. It is important to note that the authors of the IEO 2004 also project global natural gas consumption to increase by an average of 2.1% per year from 2001 to 2025.

The global reserves of natural gas total 6076 trillion cubic feet (Tcf).[2] The United States contributes 187 Tcf to this total.[2] William L. Fisher, Director of the University of Texas at Austin's Jackson School of Geosciences, has estimated that the United States has a remaining natural gas resource base of 2400 Tcf.[3] Of this 2400 Tcf, "about 800 Tcf is yet to be discovered...about 600 Tcf will come from so-called basin center, generally low-permeability formations; about 300 Tcf will come from shales and coal beds; something on the order of 500 Tcf will come in the form of reserve growth from existing fields; and current proven reserves amount to 177 Tcf." Because of the uncertain nature of this estimated resource base, it is not clear whether this entire estimated resource base will eventually be considered to satisfy the definition of reserves.

The calculations that you can perform by using the web pages linked to this page (see the menu at the left) are meant to help you gain a feel for the "lifetimes" of the fossil fuels. At present, there is one method available on these web pages to estimate the "lifetime" of natural gas. It is a simple method, in which the annual percentage change in consumption is assumed to be constant for all time. This method is implemented on the page listed on the menu on the left. This page enables you to change various inputs, such as the amount of remaining natural gas reserves, the rate of consumption, and the annual percentage change of the consumption rate.

NOTE: To use this page, you must be using a browser that enables Java to JavaScript communication. PC users using Internet Explorer or Netscape Navigator 7.0 will probably experience no problem. Mac users: OS 9.1 with Netscape 7.0 works. Also OS X with any latest-edition browser will probably work. The author has not tested these pages on all different platform/browser combinations.

Because world events can significantly alter the rate of consumption, no claim is made about the accuracy of the predicted "lifetimes". Please keep in mind that it is most useful to simply allow the numbers to vary and see how the "lifetime" of the fossil fuel changes.

[1] Strictly speaking, energy is not “consumed”, but rather is converted into different forms. When most people speak of "consuming" energy, the process they are describing is the conversion of energy to useful work or to energy stored in the form of (new) chemical bonds. During the conversion process, some of the available useful energy is transformed into radiant energy (light) and thermal energy (heat).

[2] Energy Information Administration, Office of Integrated Analysis and Forecasting, International Energy Outlook 2004, rep. no. DOE/EIA-0484(2004), U.S. Department of Energy, Washington, D.C. (April 2004).

[3] William L. Fisher, "Domestic Natural Gas: The Coming Methane Economy", Geotimes, pp. 20-22, November 2002.