The Second Frontier Formation in the Emigrant Springs area is a moderately tight, gas producing sandstone reservoir with absolute permeabilities averaging less than 1.0 md. Well completion in the area involves setting casing through the zone, perforation of the casing, and stimulation by hydrofracturing. Well evaluation is typically accomplished using production history and decline curves. Further development in the area, in terms of step-outs and infill drilling, demands techniques for predicting well productivity using wireline log data obtained prior to the setting of the casing.

In an effort to quantify these values, a petrophysical analysis was performed. Open-hole well logs, sidewall cores, and specialized logs such as Combinable Magnetic Resonance (CMR) and Formation Multi Imager (FMI) were used to compute parameters such as effective porosity, water saturation and permeability. The relationships between these parameters and productivity indicators, such as initial production (IP) and estimated ultimate recovery (EUR), were then studied.

Furthermore, this analysis included a review of depositional environments in the area to identify any effects on production. This examination included petrographic analysis of drill cuttings, and the interpretation of FMI logs, which were then coupled to previous petrographic work that considered similar data from the same general area1 .

Results indicate that the product of log-derived porosity, permeability, gas saturation and pay thickness are indicators of IP and EUR. Additionally, this analysis demonstrates that productivity indicators are strongly influenced by geometric, textural, and diagenetic characteristics of the reservoir rock (lithofacies) that are largely a function of depositional environment.

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