Hydraulic fracture design optimization for deep foothills gas wells

The Deanne Glauconitic A pool is located approximately 80 km northwest of Rocky Mountain House, in the Alberta foothills. The reservoir is a thin, tight sandstone, located at a depth of approximately 3,500 m. In situ stress conditions in this area have been strongly influenced by the orogeny of the Rocky Mountains, with significant tectonic stresses imposed on the rock matrix. This high stress regime poses a major challenge to the very costly hydraulic fracturing treatments. A review of off-setting fracture treatments in the area showed that approximately 50% of previous treatments suffered from premature screenout, with poor post-stimulation productivity. A comprehensive study was conducted to understand the cause(s) of previous failures, and to make recommendations for an optimal fracture design. Once the key fracturing design parameters were identified, a recompletion design was carried out, including a refracture treatment, which successfully placed all of the fracture sand. This paper describes recommended procedures to optimize hydraulic fracture design for a deep gas reservoir in the foothills. These procedures include: Review off-setting fracture treatments; Identify the key drivers for successful sand placement; Examine core samples and design the fracture fluid, with emphasis on minimizing rock-fluid interactions; Model the hydraulic fracture using a 3D simulator; Size the fracture to optimize economic returns; Design the recompletion program and estimate costs; Implement the fracture treatment with stringent QA/QC processes; and, Post-fracture analysis by means of net pressure and radioactive logs to validate the fracture design.