Wellbore to fracture proppant-placement-fluid rheology

• Novel viscoelastic surfactants can reduce viscosifiers and breakers in fracturing.
• Viscoelastic surfactants thicken in a discrete shear regime as tunable fluids.
• Extensional flow from perforations induce fluid resistance for proppant transport.
• The degree of thickening determines the degree of induced viscoelasticity.

Novel reservoir engineering displacement fluids (cetyltrimethylammonium bromide and sodium salicylate in water) are examined as candidates for proppant placement during fracturing. The need for additional crosslinkers, breakers or contact with hydrocarbons to change the viscosity is eliminated. These materials have a viscoelastic response governed by flow. Two fluid compositions are investigated in relation to Newtonian fluids of similar base viscosity to determine how shear induced structures (SIS) influence flow properties in the near-wellbore region of a fracture. In Couette flow, the fluid displays shear thickening and thinning within a discrete shear regime. Extensional flow tests in a microfluidic device reveal a flow resistance up to 25 times higher than Newtonian fluids. This extra flow resistance is due to an induced intermicellar network and has potential application for improved proppant carrying after injection via a perforation. Particle image velocimetry is used to visualise the entrance flow in a fracture. Instabilities are reduced as flow through the perforation increases. The viscosity contrast ratio between zero-shear viscosity and maximum viscosity response determines the extra proppant carrying capacity.