High-Resolution Numerical Modeling of Complex and Irregular Fracture Patterns in Shale Gas and Tight Gas Reservoirs
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AbstractVarious models featuring horizontal wells with multiple fractures have been proposed to characterize flow behavior over time in tight and shale gas systems. Currently, only very little is known about the effects of nonideal fracture patterns and coupled primary-secondary fracture interactions on reservoir performance in unconventional gas reservoirs.We developed a 3D Voronoi mesh-maker that provides the flexibility to accurately represent various complex and irregular fracture patterns. A numerical model was developed based on such fracture concepts to assess the potential performance of unconventional gas reservoirs. We conducted simulations using up to a half-million cells and considered production periods that are orders of magnitude longer than the expected life of wells and reservoirs. Our aim is to account for a wide range of flow regimes that can be observed in irregular fracture patterns, and to fully assess even slight nuances in flow behavior.We investigated coupled primary-secondary fractures, with multiple vertical hydraulic fractures intersecting horizontal secondary "stress-release" fractures. We studied irregular fracture patterns to show the effect of fracture angularity and nonplanar fracture configurations on production. The results indicate that the presence of high-conductivity secondary fractures results in the highest increase in production, while, contrary to expectations, strictly planar and orthogonal fractures yield better production performance than nonplanar and nonorthogonal fractures with equivalent propped fracture lengths.
