Unconventional natural gas resources

Abstract

The most-often mentioned sources of unconventional natural gas are tight gas formations, coal seams, aquifers, and Devonian shales. However, there are other unconventional sources such as methane hydrates, ultra-deep formations, and abiogenic gas. The chemical composition of gas from unconventional sources is essentially the same as natural gas from conventional resources which varies with the producing horizons. The major difference between the two is the nature of the reservoir. In unconventional sources the reservoir rock also may be the source bed, the permeability and porosity of the reservoir may be significantly less, the reservoir actually may be an aquifer, and/or the reservoir rock may not be the commonly accepted sandstone or carbonate formation. Gas production from the unconventional resources is technically more difficult, usually more expensive, and less predictable than conventional sources. This study describes the different unconventional natural gas resources. The difficulties in terms of production and the degree of success with producing the resources are discussed. 14 references.