UC Berkeley

Copyright 2015, Unconventional Resources Technology Conference. The canonical monitoring geometry for hydraulic fracturing processes consists of a horizontal treatment well and a roughly parallel observation well that contains an array of acoustic sensors. This is a cost-effective method because it allows for relatively high-resolution monitoring with a low number of cross-well geophones. However, there is a significant drawback with this type of monitoring technique. Specifically, moment tensor inversion suffers based on a small solid angle, which is due to limited aperture. While the current literature suggests that additional monitoring wells are necessary to gain a better understanding of microseismic attributes, that solution is accompanied by a much higher cost. Another proposed solution to this problem is through the use of large surface monitoring arrays; however, what is gained in azimuthal coverage is often lost due to the introduction of significant noise. In an effort to minimize overall cost and improve the understanding of microseismic source mechanisms with this basic monitoring geometry, we propose a new approach that relies primarily on spectral analysis. Though careful exploration in the frequency domain, specific parameters like center frequency and bandwidth, combined with knowledge of pumping parameters, lead to inferences regarding microseismic source mechanisms that would be otherwise unavailable. The benefits of this approach are significant due to the fact that an understanding of microseismic source mechanisms can lead to a greater awareness of new fractures and associated permeability of the fracture network. Moreover, circumventing the limitations accompanied by the traditional survey geometry due to limited aperture while minimizing overall cost can have a significant impact on the viability of new hydraulic fracturing processes.