Arnold, Bill W.¹, J. Matthew Herrin², Paul M. Basinski³
(1) Sandia National Laboratories, Albuquerque, NM
(2) New Mexico Institute of Mining and Technology, Socorro, NM
(3) El Paso Production Company, Houston, TX

ABSTRACT: Statistical and Geostatistical Analyses of Coal-Bed Methane Production in the Raton Basin, New Mexico and Colorado

Coal-bed methane production may be influenced by multiple factors, including fracture network characteristics, local geologic structure, regional stress, coal thickness, depth, hydrology, and pressure history. Understanding the relative importance of these factors potentially contributes to the optimization of production development.
Average daily gas and water production from 284 CBM wells in four El Paso Production development pods in the Raton Basin were analyzed. Stepwise linear regression was used to estimate the relative importance of independent variables, including the first and second derivatives of upper surface of the Trinidad Sandstone, total coal thickness, groundwater total dissolved solids, and duration of production, to the gas and water production. Variogram analysis was used to assess the spatial continuity in production.
The correlation analysis using stepwise linear regression indicates that the total coal thickness in the Vermejo and Raton Formations accounts for about 14% of the variability in average daily gas production. The slope of the Trinidad Sandstone parallel to maximum principal horizontal stress (N 5 E) accounts for about 5% of the variability in average daily gas production. Significantly better correlation exists between the independent variables and the ratio of gas to water production, with 44% of the variability in the gas/water ratio accounted for by the slopes of the Trinidad Sandstone parallel and perpendicular to maximum principal horizontal stress. Geostatistical analysis with variography indicates that the spatial correlation in gas and water production among wells extends about 3 to 6 kilometers.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004