Analyzing Hydraulically Fractured Gas Well Performance in the Greater Green River Basin of Wyoming*
Hydraulic fracture stimulation often dictates the economic outcome of wells completed in low permeability gas reservoirs. Evaluating well performance - the rate and pressure behavior of a well over its productive life - provides the opportunity to discover the key elements driving stimulation and completion effectiveness in any particular environment. This presentation demonstrates the integrated use of reservoir engineering, petrophysical and geologic analysis to evaluate well performance, identify flow regimes and distinguish between reservoir and completion induced behavior. Tools used include well log analysis (for pay identification and petrophysical calculations), the reciprocal productivity semi-log method (to normalize the inevitable variations in flow rate when evaluating the post-linear, infinite acting radial flow period), fractured well type-curve analysis, pressure buildup analysis and numerical simulation. The main emphasis is an expanded discussion outlining the fundamentals of production data analysis. Case studies from the Greater Green River Basin of Wyoming of single wells and entire fields draining low permeability gas reservoirs are used to demonstrate this methodology, and significant reservoir, completion, and production factors affecting well performance are identified as an outcome. The impact of critical completion and production factors will be revealed and discussed. These problems and factors include wellbore liquid loading (in reducing or eliminating the effective hydraulic fracture length), treatment sizing, treatment isolation strategies and sequencing of multi-pay completions, treatment flowback strategy, use of velocity/ tubing strings and selection of landing depths, and shutting in a producing well. Remedies are suggested for stimulation and completion induced problems.