Development of a Viscoelastic Property Database for EOR Polymers

Abstract

Partially hydrolyzed polyacrylamide (HPAM) and related polymers are widely used as mobility control agents in all chemical EOR applications, and an accurate characterization of their apparent viscosity in the reservoir rock is crucial for design and performance evaluation of these processes. Their apparent viscosity in porous media generally decreases as flow velocity increases; however, beyond a certain critical velocity, the apparent viscosity sharply increases, showing shear-thickening behavior. A procedure to predict both the shear-thinning and shear-thickening apparent viscosities, from the rheometer-measured shear and oscillatory viscosities, has been developed earlier and validated with corefloods (Delshad et al., 2008). In addition to the shear viscosity database developed earlier (Lee et al., 2009), a database of the oscillatory viscosities of the EOR polymers was therefore developed for wide ranges of polymer concentration, NaCl salinity and calcium content, and temperature. The generalized Maxwell model (GMM) is employed to estimate the relaxation time of the polymer solution, by making non-linear fitting of the measured G' and G" data to GMM. Empirical correlations were developed to predict the relaxation time, which is subsequently used to quantify the shear-thickening portion of the apparent polymer viscosity under different process conditions. The apparent viscosity estimated matches reasonably with the available coreflood data.

Review on Polymer Flooding: Rheology, Adsorption, Stability, and Field Applications of Various Polymer Systems

“…Storage and loss moduli decrease due to the addition of salt. 98,99 Modulus crossover point of the copolymer did not significantly change with temperature. Rashidi et al 56 evaluated the effect of the degree of sulfonation on shear stability and found that the increase in the degree of sulfonation has increased the shear stability due to increased rigidity.…”

Oil displacement mechanisms of viscoelastic polymers in enhanced oil recovery (EOR): a review

“…This model accounts for both rheological behaviors and was successfully used to history-matched data taken from published laboratory reports. Kim et al (2010) used this viscoelastic model to develop a database for HPAM polymer solutions for a wide range of polymer concentration, salinity, and hardness, and temperature making it more practical to quantify the apparent viscosity of the polymer solution at reservoir conditions. Recently, further improvement of the parameters of this model was presented by Sharma et al (2011).…”

Microvisual investigation of polymer retention on the homogeneous pore network of a micromodel

“…The most sensitive polymer to brine and multivalent ions is hydrolyzed polyacrylamide. This sensitivity results in a loss of viscosity and thus increasing mobility (Kim et al, 2010). As the literature proposed, the polymer displaced by 5 wt% NaCl dyed-water has less retention on the pore walls as compared to the polymer retention of very low salinity water.…”