Rheological Assessment of the Elasticity of Polymers for Enhanced Heavy Oil Recovery

Abstract

More recently polymer flooding recovery processes are becoming increasingly attractive due to the improvements in polymer manufacturing, hydration and implementation successes worldwide. This is especially true in the application of polymer for enhancing heavy oil recovery. It has been suggested that the elastic nature of the polymer is equally important to the viscous properties. In the present study, a specialized rheometer was used to determine the viscoelastic properties of both hydrolyzed polyacrylamides (HPAM) and hydrophobically associating polyacrylamides (HAP) used in heavy enhanced oil recovery (EOR) processes. The rheometer has the capability to measure rheological properties in porous capillary plugs providing a more representative picture of non-Newtonian fluid flow in reservoirs. The rheological parameters were determined as influenced by polymer type, concentration, molecular weight, hydrophobicity, salinity and temperature. Increases in elastic tendencies were observed as a function of the first four; however, salinity and temperature were found to have a slightly negative effect. A medium density, hydrophobic polymer showed an earlier onset of elastic contribution at in-depth reservoir shear rates as determined by its Weissenberg number. For heavy oil reservoirs utilizing higher polymer concentrations, the viscoelastic properties of a polymer system should be evaluated in the screening process. Recent studies suggest that viscoelastic polymers can reduce the residual oil saturation below that to waterflood with two different plausible mechanisms at play, depending whether the media is water- or oil-wet. However, in both theories, polymer elasticity is believed to be the dominant force that contributes to the additional reduction in oil saturation. Aside from measuring the elasticity directly, other parameters that quantify a polymer's elastic potential are its relaxation time and Weissenberg number; therefore, the change in these parameters with respect to dynamic shear rate or flow velocity can be further useful for screening purposes.

Assessment of Polyacrylamide Based Co-Polymers Enhanced by Functional Group Modifications with Regards to Salinity and Hardness

“…FLOCOMB C7035 is an anionic post-HPAM [18]. Through post-hydrolysis process, molecular weight, and polydispersity (i.e., molecular weight distribution) were increased so as to provide a full range of calcium tolerance thus increasing chemical stability in very hard and salty brines [19,20].…”

“…The co-polymers investigated in this study were FLOCOMB, an anionic post-HPAM [18] with increased molecular weight and polydispersity [19,20], AN132 VHM, a sulfonated polyacrylamide copolymer with a sulfonation degree of 32 mol % and a high molecular weight [19,21,22] SUPERPUSHER SAV55, having a functional groups that are similar to AN132 VHM, but with a higher degree of sulfonation [21] and THERMOASSOCIATIF, a copolymer showing thermo thickening behavior [21,23,24].…”

Understanding the flow behaviour of copolymer and associative polymers in porous media using extensional viscosity characterization: Effect of hydrophobic association

“…[8,[49][50][51][52][53][54][55][56] The longest relaxation time determined by the cross-over method was reported to be within the same range of rouse relaxation time. [56] Wilton and Torabi [57] recently used a specialized oscillatory V-E rheometer, based on oscillatory flow, but with the capillary plug for characterizing the EOR polymers. Seright et al [20] reported the inability of shear rheology to distinguish similar shear behaviour polymers (HPAM and AP) in the oscillatory field, thereby resulting in a similar value for G' and G".…”

Polymer Injectivity: Investigation of Mechanical Degradation of Enhanced Oil Recovery Polymers Using In-Situ Rheology

“…Regardless of the nature and differences in the molecular structure of these two polymers, polymer viscosity is the main physical property in the context of polymer flooding. Polymer viscosity depends on polymer molecular structure, molecular weight [3], polymer concentration [4], salinity [5,6], temperature [7,8], degree of hydrolysis [9], pH [10], flow model and type of forces dominating the flow [11].…”