Induced fracture complexity maximization, in addition to the primary hydraulic fracture, to improve the recovery efficiency or productivity of gas or liquids in unconventional reservoirs has been accepted and fully implemented by the industry. As a result, stimulation fluids and/or completion strategies have been engineered to maximize induced fracture complexity in many unconventional reservoirs. In typical horizontal completions, induced fracture complexity with sustained conductivity is clearly beneficial for the productivity of nanodarcy (nd) shales, although this might not be a requirement for all unconventional reservoirs, especially tight sands.
In some unconventional reservoirs, operators have observed similar productivity in wells with predominantly planar fractures compared to wells that appear to have more complex fractures. This paper, supported by extensive reservoir simulations, aims to develop criteria for situations in which induced fracture complexity and sustained conductivity are required and when they are not. The simulations include a reservoir permeability range of 10 nd to 0.001 md and a complexity or secondary fracture conductivity of 1 to 5 md-ft. The results show that the fracture complexity and sustained conductivity are generally important for reservoir permeabilities lower than 100 nd for gas and 500 nd for liquid-producing reservoirs.
Based on these results, an optimized completion strategy is suggested to maximize the productivity or recovery factor (RF) in unconventional gas- and liquid-producing reservoirs.