A number of injection/fall tests using the Nolte G-function and after closure analyses (ACA) were performed on horizontal Marcellus Shale completions to determine the ISIP, closure stress, net pressure, fluid efficiency, reservoir pore pressure, and formation permeability. The results obtained from the G-Function analysis were verified by post-fracture history matching of the fracture treatment and production data. This information was used to modify current and subsequent fracture treatment designs.
These tests were conducted during a period of time when the well would typically sit idle waiting on the fracture treatment, allowing the well to yield meaningful diagnostic data during what would otherwise have been a period of non-productive time. The shut-in period was sufficient in all cases to achieve pseudosteady behavior, which is critical to obtain a realistic ACA for determining formation permeability and reservoir pressure.
The results of these analyses have been used to improve efficiency during field development. Core analyses and post fracture production history matching has verified the reliability of the Marcellus Injection/Fall-off program in Greene County.