Produced Watershttp://energy.cr.usgs.gov/health_environment/produced_waters/ ******************************************************************************
Two new studies examine the relationship between gas and water production over time in tight gas sand fields in Wyoming and Colorado. These studies examine fluid production from tight-gas reservoirs, which are characterized by low permeability, low porosity, and the presence of clay minerals in pore space. Production from each well is represented by two samples spaced five years apart, the first sample typically taken two years after production commenced. For each producing interval, summary diagrams of oil-versus-gas and water-versus-gas production show fluid production rates, the change in rates during five years, the water-gas and oil-gas ratios, and the fluid type. These diagrams permit well-to-well and field-to-field comparisons. Fields producing water at low rates (water dissolved in gas in the reservoir) can be distinguished from fields producing water at moderate or high rates, and the water-gas ratios are quantified.
Gas, oil and water production from Jonah, Pinedale, Greater Wamsutter, and Stagecoach Draw fields in the Greater Green River Basin, Wyoming
Gas, oil, and water production data for tight gas reservoirs were compiled from selected wells in western Colorado from the relatively shallow Paleogene Wasatch G sandstone interval in the Parachute and Rulison fields and fluvial sandstones in the deeper Upper Cretaceous Mesaverde Group in the Grand Valley, Parachute, Rulison, and Mamm Creek fields. In this study, slightly more than half the wells producing from the Mesaverde Group show decreases in water production with time. Plots of water decline versus gas decline show little relation between the two, with only the wells in Rulison field displaying some tendency for water and gas to decline proportionately. An online version of the report can be accessed at http://pubs.usgs.gov/of/2009/1290/.
Gas, oil and water production from Grand Valley, Parachute, Rulison, and Mamm Creek fields in the Piceance Basin, Colorado
Gas, oil, and water production data were compiled from selected wells in four gas fields in rocks of Late Cretaceous age in southwestern Wyoming. In all wells in all four fields examined here, water production commences with gas production—there are no examples of wells with water-free production and no examples where water production commences after first-sample gas production. The fraction of records with water production higher in the second sample than in the first sample varies from field to field, with Pinedale field showing the lowest percentage of such cases and Jonah field showing the most. Most wells have water-gas ratios exceeding the amount that could exist dissolved in gas at reservoir pressure and temperature. An online version of the report is available at http://pubs.usgs.gov/of/2010/1110/.
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