Nanoparticle and Microparticle Flow in Porous and Fractured Media: An Experimental Study

Abstract

Abstract The goal of this research was to develop methods of acquiring data about reservoir pressure and temperature, near the wellbore and far out in the formation, and correlating such information to fracture connectivity and geometry. Existing reservoir characterization tools allow for pressure and temperature to be measured only at the wellbore. The development of temperature- and pressure-sensitive nanosensors will enable in-situ measurements within the reservoir. This paper provides the details of the experimental work performed in the process of developing temperature and pressure nanosensors. The study investigated parameters involved in the mobility of nanoparticles through porous and fractured media. These parameters include particle size or size distribution, shape and surface charge or affinity to rock materials. The principal findings of this study were that spherically shaped nanoparticles with surface charge compatible with that expected in porous media are most likely to be transported successfully through formation rock, without being trapped due to physical straining, chemical or electrostatic effects. Silica nanoparticles were passed through Berea sandstone and long slim-tube sand-packs without difficulty. We found that tin-bismuth nanoparticles of 200 nm and smaller were transported through Berea sandstone. Larger particles were trapped at the inlet of the core, indicating that there was an optimum particle size range. We also found that the entrapment of silver nanowires was primarily due to their shape. This conclusion was supported by the recovery of the spherical silver nanoparticles with the same surface characteristics. The entrapment of hematite nanorice was attributed to its affinity to the porous media caused by surface charge. The hematite coated with surfactant (which modified its surface charge to one compatible with flow media) flowed through the glass beads, emphasizing the importance of particles surface charge. Preliminary investigation of the flow mechanism of nanoparticles through a naturally fractured greywacke core was conducted by injecting fluorescent silica microspheres. We found that silica microspheres of different sizes (smaller than fracture opening) could be transported through the fracture. We demonstrated the possibility of using microspheres to estimate fracture aperture by injecting a polydisperse microsphere sample. It was observed that only spheres of 20 μm and smaller were transported. This result agreed reasonably well with the measurement of hydraulic fracture aperture (27 μm) as determined by the cubic law.