Inaccessible Pore Volume of Associative Polymer Floods

Abstract

Approximately half of current oil production is from waterfloods where a major concern is mobility control of the injected phase. Addition of polymer to the injection water decreases the mobility ratio leading to greater flood efficiency, especially for recovery of viscous oil. Of the various EOR polymer formulations, newly developed associative, water-soluble polymers show special promise. We investigate, experimentally and numerically, the inaccessible pore volume (IPV), permeability reduction (Rk), and interfacial tension characteristics of 3 different molecular weight associative polymers and, for reference, a conventional hydrolyzed polyacrylimide. Previous studies of these same associative polymers revealed good secondary and tertiary oil recovery efficiency for displacement of a viscous 140 cP oil. To our knowledge, this is the first study to observe and report IPV – Rk properties of these associative polymer solutions. New experiments were conducted by injecting polymer solutions through a roughly 12 Darcy sandpack and measuring the separation between effluent concentration profiles of the polymer and the salt used as the tracer. Results are interpreted from the effluent profiles using an analytical superposition model as well as a conventional finite difference formulation. The associative polymers yield moderate to large IPV (20 to 40%) and mild Rk (1.1 to 1.5) that increases with molecular weight. Brine salinity reduces both IPV and permeability reduction. Differences between the classical interpretation, the analytical interpretation, and the numerical implementation of IPV are discussed as is the adequacy of the conventional IPV-Rk description of the mobility control of polymer.

Flow of a Cross-Linking Polymer in Porous Media

“…The model match (blue line) yields the following estimates: effective pore volume of 534 ± 12 [ml] (porosity 26.8 ± 1.3) and a dispersion coefficient of 56 ± 11 × 10 −4 [cm 2 /s] (N Pe = 6.3 ± 1.6). Because the tracer-slug size was too small to approach the injection concentration in the effluent, the analytical model was extended by superposition (Pancharoen et al 2010). …”

Supramolecular Polymer-Surfactant System for Heavy Oil Recovery

“…The main benefit of the incorporation of hydrophobic groups is as explained by Perttamo [1]: "the reorientation of the macromolecules due to polar and non-polar, results in [the] formation of hydrophobic associations between de incorporated hydrophobic groups," generating intramolecular and intermolecular associations forming supramolecular aggregates. These polymers are called associating hydrophobic polymers or hydrophobically modified polymers or for short associating polymers [1,17,19,28,29]. Under shear, these supramolecular aggregates can disassemble due to the reversible disruption of the hydrophobic bonds; therefore, at high shear rates, these systems show a remarkable shear-thinning behavior.…”

“…Resistance factor (RF) provides information on the effective viscosity of the polymer solution during flow in porous media relative to water before polymer flooding [38]; therefore, RF indicates the effectiveness of the polymer system as a mobility control agent during enhanced oil recovery (EOR) [6,19,29,40,41]. While, the residual resistance factor (RRF) measures the increased pressure drop across the porous media due to polymer retention (mechanical entrapment and polymer adsorption) [5,6,19,29,[37][38][39][40][41][42][43][44].…”

“…While, the residual resistance factor (RRF) measures the increased pressure drop across the porous media due to polymer retention (mechanical entrapment and polymer adsorption) [5,6,19,29,[37][38][39][40][41][42][43][44]. system, while for the baseline AP1 polymer, the RF value plateaued out at an average value of 2.0.…”

Upscaling Polymer Flooding to Model Sub-gridblock Geological Heterogeneity and Compensate for Numerical Dispersion

“…Depending on the molecular weight of the injected polymer and the porosity/permeability of the formation, IPV values typically are around 20% (Trushenski et al 1974) but can be as high as 30% (Lake, 1989), or 40% for associative polymers (Pancharoen, 2010). A minimum value of zero and a maximum of 0.3 have been used here.…”