Multidirectional linear trends are commonly observed in maps of microseismic events recorded during fracture stimulation. Since Fisher drew lines through an animated map of microseismic events (Fisher et al. 2002), the industry has recognized that complex-fracture patterns can develop during hydraulic fracturing. Consequently, several new complex-fracture propagation models have been introduced to "match" the stimulated reservoir volume observed in maps of microseismic events recorded during hydraulic fracturing.

Every complex-fracture propagation model requires geometric input, including a pattern of discontinuities in the rock that can dilate or propagate during hydraulic fracturing; however, defining a pattern of discontinuities is a challenging task in a subsurface rock formation that cannot be observed directly.

We present a new method for defining a geometric model for input into a complex-fracture model using microseismic events recorded during fracturing. Events are animated and planar trends are identified to define natural fracture orientation, trace length, dip angle, and natural fracture density within the stimulated reservoir volume. Statistical analysis of the natural fracture properties allows probability distributions to be defined for each fracture property, which are then used to generate stochastic natural fracture patterns for input into a complex-fracture model.

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