Beyond “dots in a box”: The Use of Tomographic Fracture Imaging (TFI)
for the Direct Mapping of Frac-Induced Fracture Networks and
Their Connection to the Natural Permeability Field.

TFI is a new method for direct 4D mapping of active fracture/fault surfaces in near real time. TFI utilizes Seismic Emission Tomography (SET) to create semblance volumes from the seismic data. SET utilizes seismic data collected by a beam forming surface array to form semblance volumes. The semblance volumes are then subject to post processing using algorithms based on empirical data on fracture distribution and geometry. The talk has two parts:

• A brief overview of the geological and geophysical basis for the TFI technology.
• A discussion of three case studies of the technology: Tumbler Ridge, B.C.; Barnett Shale, Wise county, TX; Southwestern W. VA.

Of the three studies the focus is on the results of a blind test of TFI conducted in a tight gas reservoir in the Appalachian basin of southwestern West Virginia. The goal was to monitor a nitrogen frac to determine if direct observation could be made of the frac induced “rubbilization” and its connection to the natural fault and fracture fairways that are the main producing features in the reservoir. TFI maps from a series of frac stages, were successfully tested against an array of independent data sets including field-wide pressure monitoring, FMI logs, interference testing as well as chemical and radioactive tracer testing. The independent data sets confirmed that the TFI maps of the fracture fairways and frac induced “rubbilization”, resulted in a more thorough understanding of the reservoir production with a high degree of accuracy and precision. It was concluded that TFI can yield results that give significant new insights into reservoir performance and represent a major advance over standard downhole hypocentral techniques. The study provides further confirmation that TFI is a powerful new tool for improving understanding of hydro-carbon and other fluid reservoirs.

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