The effectiveness of hydraulic fracturing in most applications is directly dependent upon the geometry of fractures created within the layered reservoir[l,2]. Therefore, design of fracturing treatments is generally based on maximizing fracture length and propped width (conductivity) while maintaining fracture height as close to pay zone height as possible [c.f. 3, 4]. In certain situations, such as the proximity of the pay zone to a water aquifer, vertical fracture extension could become critical. Hence, fracture geometry calculations that do not assume a constant fracture height have become necessary requirements for optimum treatment design.
This paper discusses a three-dimensional model, "HYFRAC", and shows its applicability to fracture geometry prediction for a wide variety of conditions. The results of the 3-D fracture analysis can be employed to validate and/or evaluate currently used models and theories of fracture growth. Comparisons will be made with Perkins and Kern predictions of constant height growth , with Geertsma-DeKlerk and with methods using downhole pressure variation to determine fracture growth and stability. Results from other current models will also be compared to HYFRAC results. Such studies will help determine the strengths and weaknesses of the available models. This will provide a better understanding of when problems require a fully three-dimensional solution and when a two-dimensional, quasithree-dimensional, or other analysis may suffice.