Transport and Plugging Behavior of Viscoelastic Suspensions in Fractured Tight Reservoirs.

Natural or hydraulic fractures in reservoirs can lead to conformance control issues and poor reservoir confinement, making fracture plugging an essential strategy for controlled fluid flow. This work has investigated the dynamics of solid particle transport and plugging behavior in fractured tight reservoirs using high- and low-permeability sand packs. Two distinct fluid systems have been studied, a polymer-solid suspension and a nanoparticle-viscoelastic surfactant suspension. Three key injection parameters were investigated: the viscosity of the carrier fluid, the concentration of the injected solids, and the particle size distribution of the solids. Results showed that using 0.5 wt % polymer concentration with 1 wt % solids can lead to 99% permeability reduction in ∼1000 Darcy sand packs. Increasing both concentrations leads to premature plugging and injectivity loss. Upscaling to 3-foot-long sand packs showed the ability of this system to plug larger fracture volumes uniformly along the length of the sand pack. For lower-permeability fractures ∼10 Darcy, it was necessary to reduce the particle size from 112 to 62.5 μm at the same 1 wt % concentration to maintain injectivity and achieve comparable plugging efficiency. Decreasing the particle size even further to the nanoscale resulted in deeper fracture penetration and 98% permeability reduction. For the nanoparticle-enhanced VES system, the absence of nanoparticles led to limited fracture plugging of 35%, but the addition of nanoparticles increased fracture permeability reduction to 99% in low-permeability fractures. High-permeability fractures showed up to 80% reduction of the permeability and an increase in the minimum pressure gradient for mobilization up to 35 psi at higher concentrations of VES and nanoparticles. This work highlights the ability of both of these systems to effectively plug fractures, with the extent of permeability reduction being subject to injection parameters such as carrier fluid viscosity, solids concentration, and solids particle size distribution that must be tailored to the fracture characteristics. These results provide valuable insight into conformance control, enabling a more efficient reservoir performance.