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 kkC, or a critical
pore-throat radius rpkC, HMWSP injection led to stable resistance
factors, with values close to the solution?s viscosity, and that, at less than
kkC or rpkC, 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.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
15 April 2011
- Meeting paper published:
11 April 2011
- Revised manuscript received:
5 June 2012
- Manuscript approved:
6 July 2012
- Published online:
27 November 2012
- Version of record:
6 December 2012
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