In 2004 the first Appalachian Basin Marcellus Shale gas well stimulation utilizing a large slickwater treatment was performed in southwestern Pennsylvania. Since that time, based upon various publically reported results, it has become the most widely discussed play in the basin with numerous operators drilling and completing Marcellus wells in Pennsylvania, West Virginia, Ohio, and New York. This wide geographic range has led to numerous different completion schemes being utilized as with geographic variation comes geologic variability within the formation itself. A primary topic of discussion has been determining the optimal size and type of stimulation treatment for a given area. This paper will discuss the stimulation treatment designed and performed on a Marcellus well operated by Guardian Exploration LLC.
The log in Figure 1 shows the Marcellus section of a well drilled by Guardian Exploration in Potter County, PA in 2007. The Marcellus lies at a depth of 5220' to 5310'. It was cased with 4–1/2" 11.6 ppf N-80 casing rated at 6700 psi working pressure. The formation was perforated in the interval between 5255' and 5301'.The formation is underlain by the Onondaga lime which should provide a good lower barrier to fracture height growth. There appears to be little if any significant barrier to upward fracture growth.
A significant part of designing the stimulation treatment for the well was the adaptation and incorporation of ideas that have proven to be successful in other shale plays such as the Barnett shale of the Ft. Worth Basin and the Fayettville shale of Arkansas. It should always be kept in mind however that what works in one area or play does not always guarantee success in another area. By their nature, shales are extremely variable and regional differences in structure, mineralogy, and other characteristics should always be considered in treatment design.