The Underground Gasification of Sub-Bituminous Coals
Authors: Jennings James W. , Evers John F. 
Published: December 2007

This paper was prepared for the Rocky Mountain Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Billings, Mont., May 15–16, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Most of the published work on the underground gasification of coal has dealt with a combination of a conventional mining process and a combustion process although a few of the experiments accomplished the combustion through bore holes. Recently, the U.S.B.M. has reported on an underground gasification test which has not used conventional mining as a part of the process.
This paper describes a process for the underground gasification of sub-bituminous coals using in-situ combustion techniques which have been developed by the petroleum industry. A brief analysis of the chemical reactions available for the process is made with emphasis placed on the effects of temperature and pressure. Water and oxygen requirements are estimated for the process. The application of existing petroleum technology is recommended and suggestions as to the possible role of the petroleum engineer in the development of the process are made.
The expected composition of the produced gas is stated and suggestions are made for its end use. Some of the operating problems of the process are discussed and recommendations are made concerning their solution. Finally, there is a brief look at the economics of underground gasification together with estimates of the required capital investment.

Introduction
Although the United States has large domestic reserves of fossil fuels and uranium ore, the most readily available and desirable of these fuels are being rapidly depleted. For example, it appears that the U. S. has produced about 1/2 of its original supply of produced about 1/2 of its original supply of natural gas. Because of the limited nature of the supply of oil and natural gas, only a minor portion of the projected energy requirements of this country after the year 2000 can be provided by the domestic reserves of these materials.
It is becoming apparent to even the layman that it is imperative for the U. S. to develop its vast coal, oil shale, and uranium resources so that the domestic energy requirements of the country may be met independently of other energy producing nations. The recent Arab oil boycott has impressed vividly on the minds of all Americans the importance of self-sufficiency in the area of energy.