The growth of a hydraulic fracture changes the hydraulic impedance at the point where the fracture intersects the well. The components of impedance can be defined in terms of fracture dimensions using elasticity relationships for a suitable fracture model. When these components are derived from measurements of pressure oscillations, the dimensions of the fracture can be calculated. This method was applied during minifracture testing in a tight gas sand well in East Texas and a coal seam methane well in Colorado's Piceance Basin. In both tests we observed shifts in oscillation frequencies and decay rates consistent with theoretical predictions. We were able to closely duplicate measured oscillations at different stages of fracture development using numerical models. Calculated fracture dimensions are in the 70 – 120 ft range. The tests established that the impedance method can be used for fracture evaluation under both cased-hole and open-hole conditions.

You can access this article if you purchase or spend a download.