Bulletin 146—Coalbed methane in the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado

Edited by W. B. Ayers, Jr. and W. R. Kaiser, 1994, 216 pp, 14 tables, 171 figs.

Coalbed methane is playing an increasingly important role in meeting the energy needs of the United States. This unconventional gas may supply 4–5% of the domestic natural gas in 1994. The San Juan Basin led the nation in coalbed methane production in 1992, when nearly 2,100 Fruitland coalbed wells produced approximately 447 billion cubic feet (BCF) of coalbed methane - 81% of the total U.S. coalbed methane production of approximately 553 BCF.

This publication discusses five areas that relate to controls on the occurrence or producibility of coalbed methane in the San Juan Basin: tectonic setting; depositional setting; fracture patterns in Fruitland coalbeds and adjacent strata; studies of hydrology, thermal maturity, and gas composition; and the integration of geologic and hydrologic studies. The research, funded by the Gas Research Institute and conducted by the Bureau of Economic Geology at the University of Texas at Austin, the Colorado Geologic Survey, and the New Mexico Bureau of Mines and Mineral Resources, was summarized in a topical report (GRI-91/0072) that had limited distribution. This publication includes reviewed papers on the San Juan Basin from that report, but omits two generic papers, and makes the research results more available to geoscientists and engineers.

The first topic, the tectonic setting of the San Juan Basin, reviews regional tectonic controls on depositional systems and coalbed attitude. Among the most important geologic factors affecting the occurrence and producibility of coalbed methane is the depositional setting, which is covered in the second part of the report; a chapter on the regional depositional setting of Fruitland coalbed methane is followed by two chapters describing local studies. Fracture patterns in Fruitland coal beds and adjacent strata are addressed in three chapters that discuss regional cleat trends and lineament analysis. Studies of hydrology, thermal maturity, and gas composition are essential to understanding and predicting regional hydrodynamics and coalbed gas content and composition; these considerations are the subject of two chapters. Finally, the last topic is the integration of geologic and hydrologic studies. In this section, the gas and water production from Fruitland coalbeds are summarized, and on the basis of the relations between production, geologic setting, and hydrodynamics, the San Juan Basin is divided into regions in which Fruitland coal beds have similar reservoir characteristics. Authors that contributed to this bulletin include: S. E. Laubach, C. M. Tremain, W. B. Ayers, Jr., W. A. Ambrose, J. S. Yeh, S. D. Zellers, N. H. Whitehead, III, R. W. Baumgardner, Jr., W. R. Kaiser, T. E. Swartz, G. J. Hawkins, and A. R. Scott.