Injection of polymeric solutions, either as slick water or cross-linked fluids, in order to propagate a fracture and distribute proppants and keep the fracture open is a common practice in hydraulic fracturing of unconventional tight and ultra-tight formations. In addition to propagation of a main fracture, polymeric fluids will be invading the already existing network of micro-fractures and extending the network connected to the main fracture. Fluid loss into the matrix rock and micro-fractures is inevitable, so is the use of a comparable fluid loss additive to reduce the filtrate volume.
Different classes of nanoparticles have been used by several researchers to carry different agents including surfactants and enzymes for hydraulic fracturing purposes. Nano-sized pores and micro-sized fractures in tight and ultra-tight formations require a nano to micro-sized fluid loss additive to improve propagation of the hydraulic fractures by efficiently reducing the fluid loss.
In this study, application of silica and polyelectrolyte complex (PEC) nanoparticles as fluid loss additives for three sets of core plugs with permeability values within the 10−5 −10−4 mD, 0.01–0.1 mD and 1–40 mD range was investigated. The nano-sized material used in this study significantly reduced the fluid loss volume for the cores with permeability values below 0.1 mD when mixed only with 2% KCl or with low concentrations of guar polymer prepared in 2% KCl.
Combination of the fluid loss additive application with chemical carrying application makes these nanoparticle systems a suitable package for hydraulic fracturing of tight and ultra-tight formations.