Influence of Weak Hydrophobic Interactions on in Situ Viscosity of a Hydrophobically Modified Water-Soluble Polymer

Polymers are attractive enhanced oil recovery (EOR) chemicals that improve sweep and accelerate production. There is an ongoing search for polymers that are more temperature-, salinity-, and shear-stable as fields in increasingly challenging environments open to EOR methods. This paper investigates one type of hydrophobically modified polyacrylamides (HMPAM), which has promising properties. This weakly hydrophobic PAM-based polymer has been characterized with regard to in situ viscosity and rheological properties. The polymer shows similar viscosity as HPAM with regard to shear and concentration dependency but exhibits significantly higher in situ viscosity. The enhanced in situ viscosity can be ascribed to flow-induced hydrophobic interactions and not permeability reduction, as is often reported. In situ rheology is concentration-dependent and between 1000–3000 ppm, the polymer changes flow behavior from near-Newtonian to rheo-thinning. This gel-like behavior cannot be explained from bulk measurements as...