Flow behavior of thermo-thickening associative polymers in porous media: effects of associative content, salinity, time, velocity, and temperature

Siv Marie Åsen,Daniel Strand,Arne Stavland

doi:10.1007/s42452-022-04961-w

Siv Marie Åsen, Daniel Strand + Show 1 more

Open Access

https://doi.org/10.1007/s42452-022-04961-w

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Abstract

Above a critical temperature, thermo-thickening associative polymers (TAPs) have a superior ability to decrease the mobility of the water phase, compared to traditional polymers for enhanced oil recovery. The ability to decrease the mobility, will be amplified at low flow velocities, and by the presence of salt, and is much higher in porous media than would be expected from bulk viscosity. In this work, we have examined TAPs ability to reduce the mobility, i.e., to increase the resistance factor. We have studied the effect of increasing the associative content, changing the porous media, changing the salinity, and scaling up the size of the porous media. How the resistance factor evolved, was studied as a function of temperature, velocity, and time. We found that a critical associative content or critical concentration of polymer was needed to achieve thermo-thickening in the porous media. As expected, thermo-thickening increased by increasing the salinity. For the relative homogenous clastic porose media investigated here, ranging from ~ 1Darcy sandstone to multidarcy sand, type of porous media did not seem to have a significant impact on the resistance factor. Time and amount of polymer injected is a critical factor: The buildup of thermo-thickening is delayed compared to the polymer front. For our tests with the weaker systems, we also observed a breakdown of the associative network at very low injection rates, possibly caused by the formation of intramolecular association.Article highlightsKey findings from our tests of thermo-thickening associative polymer for enhance oil recovery operations:At high temperature, the polymer solutions mobility in porous media is much lower than expected from viscosityAt low temperature, the flow behavior is like that of a traditional synthetic polymerThis will mean good injectivity and superior sweep, compared to a traditional polymer for enhanced oil recovery

Highlights

In polymer enhanced oil recovery (EOR) operations, polymer is added to the water phase to increase the viscosity and thereby reduce the mobility of the displacing fluid
The response ( RFpm and RFCT ) is plotted as a function of pore volume (PV) injected, where pore volume injected is related to the pore volume of the first core
In experiment 1a, 74.3 PV of 1000 ppm A06 was injected at a volumetric flow rate, Q of 1 ml/min, the flow rate was reduced to 0.2 ml/min

Summary

Introduction

In polymer enhanced oil recovery (EOR) operations, polymer is added to the water phase to increase the viscosity and thereby reduce the mobility of the displacing fluid. Standnes and Skjevrak [32] inform that of the 72 projects described in the literature, only 6 were deemed discouraging. Despite their proven success, traditional synthetic EOR-polymers have their drawbacks: Sorbie [31] state that high molecular weight is needed for high viscosity and Stavland et al [33] report that low molecular weight is desired to minimize mechanical degradation and ensure injectivity. Above a critical elongation rate, synthetic polymers tend to become shear-thickening and at an even higher shear rates, the polymer molecules are irreversibly degraded (see e.g. [2, 19, 22, 27, 33])

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