Evaluating the Effect of Natural Fractures on Production from Hydraulically Fractured Wells Using Discrete Fracture Network Models

Abstract

Summary URTeC 1581931 Many unconventional reservoirs contain natural fractures. These fractures may be non-conductive but open preferentially during hydraulic fracturing treatment, or they may be conductive prior to treatment and provide an enlarged tributary drainage volume with different lateral extents than those suggested by conventional models of unconventional reservoirs. This paper presents a Discrete Fracture Network (DFN) study of gas production from an Eastern unconventional reservoir that contains pre-existing, conductive fractures. The natural fractures are known through a combination of innovative flow logging during drilling, image logging of the wells, and Tomographic Fracture Imaging™ (TFI). Chemical frac-tracer monitoring confirms that a natural fracture network accesses a considerably larger volume of rock than the microseismic data alone would indicate. The results of these methods provide the basis for constructing a discrete fracture network model that honors the conventional microseismic data, the flow logs, and the TFI fractures. Simulations of gas production from this network model show that, although the major portion of production comes from the hydraulic fractures and nearby closely-spaced natural fractures, the tributary drainage volume of the well extends well beyond the footprint of the hydraulic fractures themselves.