Summary
Organically crosslinked gels have been used to control water production in
high-temperature reservoirs. Most of these gels consist of a
polyacrylamide-based polymer and an organic crosslinker. Polyethyleneimine
(PEI) has been used as an organic crosslinker for polyacrylamide tertiary butyl
acrylate (PAtBA) copolymer. Literature reported that PEI can also form ringing
gels with polyacrylamide (PAM) copolymers in addition to simple PAM
homopolymers.
We report a comparative study of two water-control gel systems (i.e., PAtBA
copolymer and PAM crosslinked with PEI). Several techniques were used in the
present study, including gas chromatography (GC), carbon 13
nuclear-magnetic-resonance (C13 NMR) spectroscopy, and steady-shear viscometry.
The gases produced during the reaction, structural changes, and gelation-time
data were all integrated to provide further insights into differences between
the two gelling systems.
The evolution of isobutene gas was identified at temperatures as low as 60°C
during the formation of PAtBA/PEI gels. In addition, GC studies revealed the
release of carbon dioxide (CO2) as a product of thermal
decomposition of the tBA groups on PAtBA during PAtBA/PEI gelation.
Lower initial pH values were found to delay the gelation time of the two
systems. Salts were found to increase the gelation time. This paper summarizes
these results, and investigates the main reaction mechanisms involved. It also
discusses how these new findings will affect the application of these gels in
the field.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
9 January 2007
- Meeting paper published:
28 February 2007
- Revised manuscript received:
26 October 2008
- Manuscript approved:
8 December 2008
- Published online:
1 June 2009
- Version of record:
1 June 2009
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