Microseismic Features of Gel and Water Fracturing of Tight Gas Reservoirs

We analyse the spatio-temporal dynamics of hydraulic fracturing induced microseismicity. We present a model that describes the growth of a hydraulic fracture as a geometry and diffusion controlled process. This model contributes to estimate important parameters of the fractured area and to better understand underlying physical processes. We apply this model to well documented datasets from fracturing experiments in Cotton Valley tight gas reservoir. The treatments were performed with different parameters, e.g., type of fluid, injection rate, total volume of fluid and of proppant. In case of a gel-based fracturing, the r-t diagram of microseismicity shows signatures of fracture volume growth, fracturing fluid loss as well as a diffusion of the injection pressure. In contrast, in water-based fracturing a diffusion-like growth of microseismic event cloud is not clearly observable. However, for both the gel- as well as the water-based fracturing we obtain very similar estimates of fracture geometry and hydraulic parameters of the reservoir. The difference in permeability of the particular hydraulic fractures is probably caused by the different treatment parameters.