Presented here is a new approach to hydraulic fracturing, using proppants that self-suspend in water. To form these self-suspending proppants (SSP), conventional proppant particles are encapsulated with a thin layer of a high-molecular-weight hydrogel polymer, and then dried, yielding a free-flowing granular system that can be handled much like traditional proppants. Once the SSP contacts water, the hydrogel layer expands spontaneously and it forms a space-filling cushion around each granule. These SSPs were created to address the performance limitations that exist with traditional proppants. In contrast to traditional proppants, SSPs remain well suspended and evenly distributed within fracturing fluid. The new technology can be applied to a variety of proppant substrates.
Properties of the SSP arise from the hydrogel formulation used as their coating. Upon hydration in water, the hydrogel coating around the proppant particles imbibes water quickly and swells substantially, expanding the hydrodynamic radius of the polymer-enveloped solid core. In addition, any SSP particles that settle are easily resuspended upon restart of flow. The self-suspending proppant approach delivers proppants efficiently with the hydraulic fracturing fluid and results in no observable segregation/sedimentation. Conventional breakers are used to reverse the effect of the hydrogel layer, releasing the proppant into the fracture after transport.
Conventional proppants have a tendency to settle out of the carrier fluid, causing segregation during pumping. By contrast, the self-suspending proppant technology enables complete proppant suspension until deposition in the fracture. Moreover, using SSP can eliminate the need for the viscosity and suspension properties of a gel carrier entirely, thereby reducing the hydraulic pumping pressure for proppant transport. This self-suspending proppant technology offers a promising alternative to the proppant systems currently available for hydraulic fracturing applications. The major benefit of the SSP is better placement of proppant in the fracture, leading to lower water injection requirements, lower proppant usage, and improved well productivity.