Effect of hydraulic fracture staging and size on hydrocarbon production from shale

One of the main purposes to introduce hydraulic fractures into hydrocarbon recovery in unconventional resources is to improve the connectivity between existing natural fractures and the production well. The newly formed fracture connectivity provides faster paths for the free hydrocarbon. It is however unclear how the staging and size of the hydraulic fractures affects the recovery and if there is an optimal setting to reduce the number of frack jobs so that the impact from fracking can be reduced. In the current study, we perform numerical simulations of hydrocarbon recovery process to estimate at which hydraulic fractures size and spacing the fracture connectivity, reaches its high limit and additional hydraulic fracturing does not encourage higher hydrocarbon recovery. We use Discrete Fracture Network (DFN) modeling approach, which is highly capable of representing similar fracture network observed on individual reservoir sites, for this purpose. The DFN of natural fractures is generated and horizontal production well with vertical hydraulic fractures is explicitly represented in the system. The flow boundary conditions are applied in the way that flow is directed from boundaries of the simulation domain into the production well in the domain center. Simulations are performed for different hydraulic fracture sizes and spacing, and the variable intensities of natural fracture network. The study shows that the first-year production is not effected significantly by hydraulic fractures size or spacing in dense natural fracture networks. The hydraulic fracture size is important in reservoirs with sparse natural fractures, while spacing does not play a remarkable role.