Summary
A common problem for oil production is excessive water production, which can
lead to rapid productivity decline and significant increases in operating
costs. The result is often a premature shut-in of wells because production has
become uneconomical. In water injectors, the injection profiles are uneven and,
as a result, large amounts of oil are left behind the water front.
Many chemical systems have been used to control water production and improve
recovery from reservoirs with high water cut. Inorganic gels have low viscosity
and can be pumped using typical field mixing and injection equipment. Polymer
or crosslinked gels, especially polyacrylamide-based systems, are mainly used
because of their relatively low cost and their supposed selectivity.
In this paper, microspheres (5-30 μm) were synthesized using acrylamide
monomers crosslinked with an organic crosslinker. They can be suspended in
water and can be pumped in sandstone formations. They can plug some of the pore
throats and, thus, force injected water to change its direction and increase
the sweep efficiency. A high-pressure/high-temperature (HP/HT) rheometer was
used to measure G' (elastic modulus) and G" (viscous modulus) of
these aggregates.
Experimental results indicate that these microspheres are stable in
solutions with 20,000 ppm NaCl, at 175°F. They can expand up to five times
their original size in deionized water and show good elasticity. The results of
sandpack tests show that the microspheres can flow through cores with
permeability greater than 500 md and can increase the resistance factor by
eight to 25 times and the residual resistance factor by nine times. The
addition of microspheres to polymer solutions increased the resistance factor
beyond that obtained with the polymer solution alone. Field data using
microspheres showed significant improvements in the injection profile and
enhancements in oil production.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
26 February 2010
- Meeting paper published:
24 April 2010
- Revised manuscript received:
2 August 2010
- Manuscript approved:
29 September 2010
- Published online:
7 February 2011
- Version of record:
21 February 2011
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