Flow of Hydrophobically Modified Water-Soluble Polymers in Porous Media: Controlled Resistance Factors vs. Flow-Induced Gelation in the Semidilute Regime

Abstract

Summary The associative properties of hydrophobically modified water soluble polymers (HMWSPs) are attractive for improved oil recovery (IOR) because of both their enhanced thickening capability, compared with classical water-soluble polymers (for mobility-control applications), and their permeability-reduction, or plugging, ability (for well-treatment applications). In previous works, we have studied the injectivity of HMWSP made of sulfonated polyacrylamide backbones and alkyl side chains in the dilute regime and have shown, in particular, that it was largely governed by adsorption. In this paper, we report new experimental data on the injectivity of the same class of HMWSP solutions in the semidilute regime. From membrane filtration tests at imposed flow rate, we have first observed the formation of a filter cake made of HMWSP physical gel, which remained largely permeable to polymers. Our observations are compatible with the creation of channels within the gel. This leads to a gel-filtration process, entailing modifications of the solution's viscosimetric properties, which can be explained by a rearrangement of the intra- and interchain hydrophobic bonds in the solution. The second part of our work consisted of injectivity tests in model granular packs. We have performed comparative experiments in porous media with variable permeabilities, but at the same shear rate in the pore throats. Results show that, above a critical permeability kC, or a critical pore-throat radius rpC, HMWSP injection led to stable resistance factors, with values close to the solution's viscosity, and that, at less than kC or rpC the very high resistance factors observed suggest that flow-induced gelation of the HMWSP takes place. Furthermore, resistance factors measured over the core internal sections are compatible with an in-depth formation of the gel. These insights could be of use for designing HMWSP better suited to mobility-control operations and for tuning HMWSP-injection conditions for profile/conformance-control operations.

Associating Polymer Networks Based on Cyclodextrin Inclusion Compounds for Heavy Oil Recovery

“…Although HAP-CDE system showed the highest RF, the highest RRF value was obtained in HAP-4 system, while the HAP-CDE system showed a relatively moderate RRF value. When injecting HAP-4 system, such elevated RRF value is likely to be attributed to the marked permeability reduction effect deduced by the formation of multiple layers composed of association of hydrophobic groups [28,29,32]. The moderate RRF value for HAP-CDE system indicates that the hydrophobic groups in the network have been occupied by CD groups of the CDE to form intermolecular interaction instead of polymeradsorbed layer.…”

“…When we evaluate the permanent reduction in the permeability of porous media, residual resistance factor (RRF) is utilized. If we consider that the permeability reduction is mainly due to polymer adsorption, the average hydrodynamic thickness of the polymeradsorbed layer can be calculated from the RRF according to the Poiseuille equation [28,29]:…”

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.…”

“…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. As indicated by Dupuis et al [19], these systems offer several benefits for field applications: "…reduced polymer concentration to achieve a required mobility ratio, extend the range of suitable reservoirs in terms of salinity, and facilitate the mixing, pumping, and injection procedures. "…”

“…Incremental oil recovery by polymer flooding is induced by the following mechanisms: reduction of the water-oil mobility ratio by means of the increased viscosity of the displacing phase (i.e., injected water) and reduction of viscous fingering, decrease of the water relative permeability due to polymer retention within the formation rock, diversion of the injected water to unswept reservoir regions, improvement of the water-injection profile (i.e., preventing crossflow between vertical heterogeneous layers), and the increase of oil fractional flow [4,5,[12][13][14][15][16][17][18][19][20][21].…”