Reservoirs are not homogeneous. The rock and even fluid properties varies within the same pool/compartment, sometimes even locally (anisotropic, such as permeability). read more
The sweet spots are the areas of the reservoir with highest oil saturation and permeability (among other properties) that yields - according to the assumptions, estimates and simulations made - the highest productivity indexes (ratios of well rate to the pressure drawdown) therefore the highest recovery factor. read more
Sweet spots in shale reservoirs may be defined by source-rock richness or thickness, by natural fractures, or by other factors, using geological data such as core analysis, well log data, or seismic data. read more