Geomechanical analysis of in-situ stress and its influence on hydraulic fracturing at the Wattenberg Field, Colorado

The Reservoir Characterization Project, in conjunction with Anadarko Petroleum Corporation, undertook an integrated dynamic reservoir characterization of a portion of Wattenberg Field. We have examined various well completion parameters and their influence on production. Our conclusion is that little correlation exists between the completions parameters (fluid and proppant injection) and production. The largest control on production is geologic heterogeneity. We show that stress differences exist due to faults. Stress compartments subdivide the study area and account for localized stress rotations within fault-bounded blocks or compartments of the reservoir. These faults control stress distribution throughout the reservoir and are interpreted to be the main driving factors for production variability across the study area. Wattenberg Field is located northeast of Denver, Colorado (Figure 1). The field produces from sandstones, shales, and limestones of Cretaceous age. Discovered in 1970,Wattenberg Field has produced 321 million barrels of oil and 4.5 TCF of gas. More than 11,000 vertical wells are present in the field. Since 2007, horizontal drilling has been concentrated in the Niobrara and Codell intervals where both oil and gas are present (Figure 2). For a summary of the Niobrara/Codell resource play see Sonnenberg (2015). The Niobrara and Codell are the main development targets at depths of 6000 to 8000 ft (1800 to 2400 m). The Niobrara is comprised of approximately 300 ft (90 m) of interbedded limestone, chalks, and marls. The Codell Sandstone is a siltstone interval located below the base of the Niobrara and largely considered a separate reservoir interval.