Experimental and computational evaluation of cyclic solvent injection in fractured tight hydrocarbon reservoirs

Multi-fractured horizontal wells have enabled commercial production from low-permeability ('tight') hydrocarbon reservoirs but recoveries remain exceedingly small (< 5-10%). As a result, operators have investigated the use of solvent (gas) injection schemes, such as huff-n-puff (HNP), to improve oil recovery. Previous HNP laboratory approaches, classified primary as 'flow-through-matrix' and 'flow-around-matrix' typically (1) are not fully representative of field conditions at near-fracture regions and (2) require long test times, even when performed on fractured cores. The objectives of this proof-of-concept study are to (1) design and implement a new experimental procedure that better reproduces HNP schemes in near-fracture regions and (2) use the results, simulated with a compositional lab-calibrated model, to explore the controls on enhanced hydrocarbon recovery in depleted tight oil plays. Performing multiple CO₂ and (simplified) lean gas HNP cycles, the integrated experimental and simulation approach proposed herein achieves the ultimate recovery factors in a significantly shorter time frame (25-50%) compared to previous studies. The integrated experimental and computational approach proposed herein is valuable for core-based evaluation of cyclic solvent (CO₂, CH₄) injection in tight hydrocarbon reservoirs for (1) hydrocarbon recovery and (2) subsurface greenhouse (CO₂, CH₄) gas disposal/storage applications.