Production data analysis of shale gas reservoirs

Hydrocarbon resources from unconventional shale gas reservoirs are becoming very important in the United States in recent years. Understanding the effects of adsorption on production data analysis will increase the effectiveness of reservoir management in these challenging environments. The use of an adjusted system compressibility proposed by Bumb and McKee (1988) is critical in this process. It allows for dimensional and dimensionless type curves to be corrected at a reasonably fundamental level, and it breaks the effects of adsorption into something that is relatively simple to understand. This coupled with a new form of material balance time that was originally put forth by Palacio and Blasingame (1993), allows the effects of adsorption to be handled in production data analysis. The first step in this process was to show the effects of adsorption on various systems: single porosity, dual porosity, hydraulically fractured, and dual porosity with a hydraulic fracture. These systems were first viewed as constant terminal rate systems then as constant terminal pressure systems. Constant pressure systems require a correction to be made to material balance time in order to apply the correction for adsorption in the form of an adjusted total system compressibility. Next, various analysis methods were examined to test their robustness in analyzing systems that contain adsorbed gas. Continuously, Gas Production Analysis (GPA) (Cox, et al. 2002) showed itself to be more accurate and more insightful. In combination with the techniques put forth in this work, it was used to analyze two field cases provided by Devon Energy Corporation from the Barnett Shale. The effects of adsorption are reasonably consistent across the reservoir systems examined in this work. It was confirmed that adsorption can be managed and accounted for using the method put forth in this work. Also, GPA appears to be the best and most insightful analysis method tested in this work