Summary

Interferometric imaging of microseismic data can provide high-resolution images of the subsurface. Each microseismic event can be used as a seismic source to image the subsurface in the vicinity of the event location. Combining thousands of events yields a three-dimensional image with a resolution on the order of a few feet, much finer than typical surface seismic or VSP data. These images can be combined with treatment and production data to help understand the effectiveness of a hydraulic fracturing program and identify additional drilling opportunities. We illustrate the method with a real data example from the Permian basin.

Introduction

While microseismic data have been used extensively to map hydraulic fracturing or understand microseismic source mechanisms, these data have not seen much use as sources for conventional seismic imaging of the subsurface. Microseismic events are weak compared to controlled energy sources and their origin times and locations are not known with great accuracy. The same could be said for passive seismic sources. Interferometric techniques have successfully been applied to image the subsurface using passive seismic (de Ridder and Biondi, 2010) as well as active-source (He et al, 2009) seismic data. Interferometric imaging works with passive data because it is relatively insensitive to source location and time origin, and is dependent only on knowledge of the local velocity model in the vicinity of the borehole, not on the overburden velocity. Because the effects of the overburden are removed, interferometric images can have broader frequency content and higher resolution.

We focus on a particular variant of interferometry, transmission interferometry, where P and S energy generated from microseismic events is imaged as it scatters off subsurface structures. We show it is possible to image the subsurface using microseismic energy, and use thousands of events to build up a high-resolution threedimensional image, using a microseismic dataset from the Permian basin.

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