Gas and Water Production in the Wind River Basin, Wyoming
Nelson, Philip H.1, Patrick K. Trainor2, and Thomas M. Finn1
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