SENSITIVITY ANALYSIS OF HYDRAULIC FRACTURE CHARACTERISTICS IN CARBONATE FORMATIONS OF THE APPALACHIAN BASIN

A sensitivity analysis has been performed for characteristics of hydraulic fractures induced in carbonate formations for the purpose of creating gas-storage capacity using a new method involving large-scale dissolution with acid. A realistic range of physical parameters for Paleozoic limestone formations at 1200-2500 m depth in the northeastern United States was estimated and used to predict the characteristics of fractures that could be created. The degree of influence of various parameters on fracture propagation and various methods of inducing fractures were analyzed. Fracture simulations were conducted using modeling software that has a fully 3-D fracture geometry package. The simulations, which predict the distribution of fracture geometry and fracture conductivity, show that the stress difference between adjacent beds is the physical property of the formations that has the greatest influence on fracture characteristics by restricting vertical height growth. The results indicate that by modifying the fracturing fluid, proppant type, or pumping rate, a fracture can be created with characteristics within a predictable range. Understanding the expected characteristics of induced fractures in carbonate formations improves the ability to assess the fracturing technology for use in groundwater withdrawal, solution mining, natural gas storage, and oil and gas production.