Evaluating the Impact of Waterfrac Technologies on Gas Recovery Efficiency: Case Studies Using Elliptical Flow Production Data Analysis

摘要

This paper presents results from an evaluation of water-based hydraulic fracture stimulation treatments (or "waterfracs") performed in the Bossier tight gas sand play in the East Texas Basin. The primary objectives of our study were to not only assess stimulation effectiveness, but also to compare recovery efficiencies of various waterfrac technologies. Our primary evaluation tool is a set of new decline type curves developed specifically for the analysis of production data acquired from the elliptical flow period commonly observed in hydraulicallyfractured wells completed in tight gas sands [Amini et al (2007)]. In this study we evaluated 12 gas wells from three Bossier tight gas fields located in Freestone County, Texas. Stimulation treatments for the wells in this study include water-based hydraulic fracture stimulation treatments with little or no sand, cases with large sand concentrations, as well as "hybrid waterfracs." "Hybrid waterfracs" are defined as fracture stimulation treatments where water is pumped initially to create the fracture geometry (I.e., width and length), followed by sandladen gels to transport and place sand in the fracture (presently low concentration gels are used as opposed to large concentration gels used in the 1980s). Results from our study confirm that "hybrid waterfracs" yield longer, more conductive hydraulic fractures and are more effective at recovering gas-in-place for a given well spacing. Although less expensive to implement, small "waterfracs" (with little or no sand/proppant) are less efficient at gas recovery — which suggests more wells may be required to maximize gas recovery when "waterfracs" are employed.