A study was made of stimulation treatments being conducted in the Frontier Formation, southwestern Wyoming. The purpose of the study was to determine why some treatments were successful while others resulted in inadequate production increases.

The initial step was to gather as much data as possible from treatments previously pumped. Although this information helped to pinpoint trends in the field, it was of little value in determining the cause of stimulation failure. In an effort to get more information, rninifracture treatments were pumped on new wells to determine fracture parameters. Bottom-hole pressures were also monitored during all pumping operations. Applying current technology to these data led to a better understanding of how the fracture was propagating. On previous jobs, post-fracture temperature logs consistently indicated "in-zone" treatments, which could not be supported by the interpretation of bottom-hole treating pressures. The assumption that fractures were confined in the pay zone was also disproved by post-fracture, pressure buildup tests. These tests indicated that effective propped fracture lengths were far shorter than calculated fracture lengths. The key to successful stimulation was found to be controlled fracture height throughout the fracture.

Our goal was to build an artificial barrier the length of the fracture using 100-mesh sand. Other techniques applied included lower pump rates, lowering breakdown pressures to avoid unwanted fracture geometry, and gut shooting the pay zone to predetermine the point of fracture initiation. Production results to date show a definite increase in the percentage of successful stimulation treatments.

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