Comprehensive Evaluation of the EOR Polymer Viscoelastic Phenomenon at Low Reynolds Number

Abstract

This study focuses on the investigation of the total pressure drop with regards to the shear, elongational and frictional forces experienced by the viscoelastic EOR polymers during the flow through porous media. The main analysis is performed to these forces occurring at low Reynolds numbers. Single-phase flooding experiments were conducted in Bentheimer core plugs and micromodels. Moreover, observations at pore-scale level are included by streamlines visualization analysis. The overall approach can be summarized in the following sequence: 1) Single phase polymer flooding through Bentheimer core plugs 2) Analysis regarding the correlation between the pressure drop and the apparent flow behavior. This analysis also focuses on the contribution of shear, elongational and frictional forces to the pressure drop at low Reynolds number 3) Porescale streamline visualization experiments using micromodels 4) Analysis regarding the elastic instabilities or turbulences observed during the flow at low Reynolds number from streamline visualization experiments. The preliminary evaluation from core flooding experiments shows a significant additional increase in pressure drop during the viscoelastic EOR polymers flow through porous media. The analysis regarding the cause of the additional increase in pressure drop indicates that shear and frictional forces are not the main determinants during the flooding process. This leads to a strong indication that the elongational forces experienced by the EOR polymers while flowing through the pores are the primary reason for the additional increase in pressure drop. A correlation between elongational forces and flow instabilities during the experiments was observed. It was also observed that at a given shear rate the onset of elasticity occurs. The onset of elasticity was evaluated by the observation of the normalized data obtained by taking the ratios between apparent and bulk viscosity. Further evaluations from the porescale streamlines visualization experiments showed a clear occurrence of elastic instabilities during the flow at low Reynolds numbers in the form of vortices, crossing streamlines, and steadily changing flow directions of streamlines. These flow instabilities account for the additional increase in pressure drop. This study provides a novel comprehensive evaluation approach to characterize the pressure drop observed during the EOR polymers flow through porous media with regards to their viscoelastic behavior. It should help to understand porescale polymer displacement and the contribution of viscoelastic properties on additional oil recovery. Furthermore, this paper provides evidence of the flow instabilities through visualization experiments and detailed analysis.

Coupling Microfluidics Data with Core Flooding Experiments to Understand Sulfonated/Polymer Water Injection

“…Rheometer calibration was performed prior to each measurements and viscosity measurements are performed for fresh solutions (at specific temperature), in order to avoid the possible minor changes in polymer molecular structure. For further details on the detailed rheological measurement evaluation, refer to the author’s previous publications specially [ 44 ] with further details in [ 45 , 46 , 47 , 48 , 49 ].…”

Impact of Mechanical Degradation on Polymer Injectivity in Porous Media

“…These different flow regimes have been widely discussed earlier e.g., by Chauveteau [7],Southwick and Manke [8],Stavland, et al [9],Zamani, et al [10], and Skauge, et al [11]. Due to its viscoelastic nature, its in-situ viscosity is a contribution of viscous and elastic properties e.g., shear and extensional viscosity, respectively [12].…”

On the Role of Polymer Viscoelasticity in Enhanced Oil Recovery: Extensive Laboratory Data and Review

“…Another important dimensionless number describing the fluid’s viscoelastic behavior is the Deborah number D e which is defined by: where v s is the superficial flow velocity of the fluid in m/s and L the flow length along which the fluid flows in m. In addition to the previously defined Weissenberg number, the Deborah number allows for a quantification of the elastic strain [ 25 , 60 ]. In contradiction to the definition given by Howe et al [ 25 ], Macosko [ 54 ] defines De as the ratio of relaxation time to the characteristic flow time t ( D e = λ/t).…”

“…Therefore, it is necessary to measure the rheological properties of the viscoelastic polymer solutions within porous media. Moreover, a combination of both rheometer data and data obtained from flooding experiments within porous media (e.g., sand pack, core plugs and micromodels) allows the correction of the shear rate [ 60 , 63 , 66 , 72 , 84 ]. This is necessary because shear rates are only calculated in flooding experiments and, hence, have a certain degree of inaccuracy.…”

“…This is further underlined by measured relaxation times [ 69 ]. In core flooding experiments, an increasing viscoelasticity is observed as well for an increasing polymer concentration [ 60 ].…”