Flow of concentrated viscoelastic polymer solutions in porous media: effect of M_W and concentration on elastic turbulence onset in various geometries

Abstract

Viscoelastic polymer solutions exhibit a variety of flow instabilities and in particular, in mixed shear and extensional flow, elastic turbulence. Coincident with the transition to turbulence is additional dissipation that, in porous flow, may be characterised as an increased apparent viscosity. We report elastic turbulence and apparent thickening in the flow of polymer solutions both in rock samples and in microfluidic analogues and we correlate the onset of thickening and turbulence with rheological measurements. Contrary to expectations, the characteristic relaxation time associated with the transition to turbulence is found to be independent of polymer concentration over the range studied (10c* ≲c≲ 100c*). Furthermore, this characteristic time scales with the square of molecular weight. Thus the characteristic time associated with the transition to turbulence is not the linear-viscoelastic timescale usually measured but rather scales as a dilute Rouse time despite being an entangled system.

A Comprehensive Combination of Apparent and Shear Viscoelastic Data during Polymer Flooding for EOR Evaluations

“…It is evident from the plot that at a certain shear rate the onset of elasticity occurs. This is consistent with results obtained by Howe et al, [26] and clearly indicates non-dependence of this onset on polymer concentration. This is contrary to the generally accepted assumption often made by the authors in petroleum related literature.…”

“…It could be inferred then, as reported by Hincapie, [15], Howe et al, [26] that flow instabilities are related to elastic turbulence. …”

“…As reported by Howe et al, [26], this manner of plotting is equivalent to plotting the measured pressure during core experiments divided by behaviour expected according to Darcy's equation.…”

“…Since the purpose in this work was to describe that onset or shear thickening, a different approach was chosen. Howe et al, [26] proposed a plotting approach from observations in microchannel that seem to be useful, as expressing the behaviour observed in core plugs. The suggested evaluation is based on plotting the normalized data obtained by taking the apparent viscosity (measured during core experiments) divided by bulk viscosity (rheometer) against the apparent shear rate.…”

Extra dissipation and flow uniformization due to elastic instabilities of shear-thinning polymer solutions in model porous media

“…However, these solutions behave very differently to Newtonian fluids. They exhibit shear-tinning properties, 4 viscoelastic behavior, 5 and slippage at the wall. [6][7][8] Above the overlap concentration and for sufficiently high flow rates, elasticity and shear-thinning become very important.…”