Gas and Water Production in the Wind River Basin, Wyoming

Nelson, Philip H.¹, Patrick K. Trainor², and Thomas M. Finn^1
1U.S. Geological Survey, Denver, CO
²Colorado School of Mines, Golden, CO

     We examine gas and water production from low-permeability reservoirs in the Wind River Basin, where water is commonly produced from most gas fields. Plots of gas production, water production, and water-gas ratio illustrate the variability of fluid production within fields (time dependence). Representative daily rates derived from these plots permit field-to-field comparisons (spatial dependence).
     As an example of time dependence, plots of gas and water production from overpressured sandstones in the Upper Cretaceous Cody Shale in the Madden area show that water is produced from all intervals and that water production commences with gas production. Gas production usually decreases with time, but in some cases remains unchanged (within a factor of two) for as long as 13 years. In 11 cases of decreasing gas production with time, water decreases with time in 6 cases, remains unchanged in 3 cases or increases in 2 cases. The water-gas ratio increases, decreases, or remains unchanged with time, with no apparent dependence upon gas or water behavior. In brief, gas production rate, water production rate, and water-gas ratio over time are highly variable among wells and among production zones.
     To examine spatial dependence, average daily fluid production rates after two years of production are plotted on log-log plots of water and gas rates for a number of fields in the basin. Gas and water rates vary by more than ten-fold from well to well within fields. In five “tight” gas fields, gas production ranges from 300 to 10,000 mcf/ day, water production ranges from 1 to 100 barrels per day, and the water-gas ratio ranges from 1 to 30 barrels per mmcf. The water-gas ratio does not appear to depend upon thermal maturity.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah