Effects of Diffusion, Adsorption, and Hysteresis on Huff-n-Puff Performance in Ultratight Reservoirs with Different Fluid Types and Injection Gases

Cyclic solvent injection, known as huff-n-puff, is one of the promising techniques for enhancing oil recovery from shale reservoirs. This study investigates huff-n-puff performance in ultratight reservoirs by conducting large-scale numerical simulations a wide range reservoir fluid types (retrograde condensate, volatile oil, and black oil) different injection gases (CO2, C2H6, C3H8). A dual-porosity compositional model utilized to comprehensively evaluate impact multicomponent diffusion, adsorption, hysteresis on production each retention capacity gases. The results show that process improves 4–6% when injected with 10% PV gas. Huff-n-puff efficiency increases decreasing gas-oil ratio (GOR). C2H6 provides highest systems, CO2 retrograde condensate type. Diffusion adsorption are essential mechanisms be considered modeling gas However, relative permeability effect not significant. GOR, while decreases increasing GOR. Oil density reduction caused diffusion observed more during soaking period considering low prediction error, showed noticeable error.