James R. Lancaster¹, John H. Dolloff²

(1) Evaluations, Inc, Littleton, CO
(2) Ripley Energy Associates, Golden, CO

ABSTRACT: Gas Storage Capacity of the Lewis Shales, San Juan Basin, New Mexico and the Sand Wash Basin, Colorado is Estimated from Log-derived Total Organic Carbon

An application of laboratory core and sample analyses for determining gas storage capacity from total organic carbon is compared with a study using wireline logs to compute total organic carbon. Results of log-based total organic carbon converted to gas storage capacity are comparable to those determined with laboratory procedures. Data are presented for the Late Cretaceous Lewis formation on wells located in the San Juan Basin, New Mexico and the Sand Wash Basin in Colorado. The well-documented San Juan Basin example is typical of currently developing gas production from previously unrecognized fractured Lewis Shale intervals.

Using previously published table data, equations were generated to compute gas storage capacity in standard cubic feet per ton from total organic carbon values. This presentation includes illustrations of the excellent correlation of data derived from both techniques in the San Juan Basin well. It also presents log-derived total organic carbon and adsorbed gas in the Sand Wash Basin, which suggest even greater gas storage capacity in the Sand Wash Basin than in the San Juan Basin.

Producing gas directly from source rocks in re-completed existing cased well bores, as in the San Juan Basin, may be a viable low-cost means of increasing gas production in the Sand Wash and other basins.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado