Fluid Production Characteristics in Pinedale and Jonah Fields

Abstract

Gas, oil, and water production data were compiled for selected wells in Pinedale and Jonah fields, Wyoming, for the purpose of quantifying the fluid production from two tight gas systems. Production of gas, oil, and water from each well is represented by two samples taken five years apart, with the first sample typically taken two years after commencement of production. For each well, summary diagrams of oil versus gas and water versus gas production show fluid production rates, the change in rates after five years, the water-gas and oil-gas ratios, and the fluid type. These diagrams allow well-to-well and field-to-field comparisons. Fields producing water at low rates (with a lower limit based on water vapor 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 production rates are higher in Jonah field than in Pinedale field at both the first and second samples, and the average gas production rate for the second sample is about half that of the first sample for both fields. Water production rates are generally substantially higher in Pinedale than in Jonah, and water–gas ratios in Pinedale are roughly a factor of ten greater in Pinedale than in Jonah. Gas and water production rates for each field are fairly well grouped, indicating that Pinedale and Jonah fields behave as distinct but fairly cohesive gas–water systems. In particular, Pinedale field appears to be remarkably uniform in its flow behavior with time. Jonah field, although internally faulted, exhibits a small spread in first-sample production rates. In all wells examined from the two fields, water production commenced with gas production—there are no examples of wells with water-free production and no examples where water production began after first-sample gas production. Water production rates declined in all wells in Pinedale field from the first to the second sample, whereas in Jonah field, half the wells showed increases and half showed decreases during the five-year period. Most wells had water–gas ratios exceeding the amount of water that could exist as water vapor in gas at reservoir pressure and temperature.