Recoverable resources are the subset of the total resource base that is thought to be technically recoverable; the technology exists to make its extraction possible. This subset is further divided into discovered and undiscovered resources. Discovered recoverable resources are those in a known location. That is, those reservoirs that geologists have actually located through exploration. Discovered recoverable resources include current production, all past production, as well as the gas that is remaining to be produced (known as ‘reserves’). Economically recoverable resources are those natural gas resources for which there are economic incentives for production; that is, the cost of extracting those resources is low enough to allow natural gas companies to generate an adequate financial return given current market conditions. However, it is important to note that economically unrecoverable resources may, at some time in the future, become recoverable, as soon as the technology to produce them becomes less expensive, or the characteristics of the natural gas market are such that companies can ensure a fair return on their investment by extracting this gas. Those resources that have been discovered, and for which a specific reservoir location is known, can further be broken down into those resources that are economically recoverable, and those that are economically unrecoverable. This differs from technically unrecoverable resources, in that the technology exists (or is foreseeable in the near future) to get economically unrecoverable resources from the ground, but the economics do not exist to make the production of this natural gas profitable. Those discovered, technically and economically recoverable resources are further broken down into different types of ‘reserves’. In general, reserves can be broken down into two main categories – proved reserves, and other reserves