Abstract
In the absence of natural fractures, hydraulic fractures can open against the minimum principal stress and propagate along continuously through the formation. However, field observations and microseismic (MS) activity suggest that, natural fractures can reactivate upon stimulation: forming complex/sheared discrete fracture networks (DFNs). Current industry practice primarily utilizes MS events alone to determine the extent of reactivation within a DFN and consequently the stimulated rock volume (SRV). However, MS activity does not necessarily distinguish between dry (i.e. reactivation with non-conductive fractures) vs. wet events (i.e. reactivation with conductive fractures). Indeed, wet events are most likely to contribute towards a Productive-SRV as these conductive fractures have an increased chance to remain open during production. This paper presents a series of geomechanical sensitivity analysis that quantify the difference between fracture events within the framework of a complex discrete fracture network simulator coupled with fluid flow and fracture reactivation. Our results show that the extent of Productive-SRV is controlled primarily by a combination of reservoir, geomechanical and stimulation parameters. These parameters include: DFN geometry (e.g. patterns, spacing, density, and orientation), stress anisotropy/isotropy, frictional strength, the duration of stimulation, and the number of stages. Results are further coupled with an unconventional reservoir simulator to quantify ultimate recovery/production for different scenarios. This integrated study/workflow provides guidelines in the field to optimize stimulation operations and to better interpret microseismic field data.'ép.
