Solid-shelled microemulsion with capabilities of confinement-induced release for improving permeability of reservoirs

Low permeability is one of major challenges associated with ineffective recovery of hydrocarbon from reservoirs. Here, we describe a novel approach to selectively removing pore blockages by asphaltene-based particles and grains, thereby improving the permeability of hydrocarbon reservoirs. This approach relies on the size-selective breakage and release of a solvent in confining regions of porous media. Such microspheres were prepared by the encapsulation of toluene emulsion droplets with silica-based solid shells. Dynamic light scattering (DLS), ultraviolet-visible (UV-vis) spectroscopy, zeta potential and optical microscopy techniques and scanning electron microscopy (SEM) technique were used to investigate their structural characteristics and stability and release behavior. The microspheres were found to be uniform in size (1-3 µm) and had a smooth surface with a shell thickness of 100-150 nm that can be ruptured under external hydrodynamics forces in narrow channels. Sand column tests revealed that when a limited amount of solvent was used, solvent-loaded microspheres could double the recovery of heavy oil, compared to the same amount of free solvent, in a model reservoir. The enhancement in the recovery was mostly attributed to the avoidance of random and uniform distribution of the solvent in the porous media and the selective localization of the solvent at confined regions. Such breakable microspheres can provide an effective approach to eliminate asphaltene-based pore blockages hindering hydrocarbon recovery.