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POLYMER GELS FOR IMPROVING OIL RECOVERY IN WATERFLOODS AND CO2 FLOODS
For Profile Modification and to Improve Sweep Efficiency and Conformance
Many waterfloods and CO2 floods suffer from premature breakthrough of the injected fluids at
producing wells, which prevents efficient sweep and limits oil recovery. The subsequent production of
high volumes of water and/or CO2 increases operating cost and shortens the economic life of the project.
Breakthrough usually occurs if natural fractures are present that lead to poor areal sweep (see Figure 1),
or if highly permeable matrix layers or “streaks” exist in the reservoir that lead to poor vertical sweep (see
Figure 2), both of which can provide conduits for fluid flow directly between injector and producer wells.
By-passed oil
By-passed oil
Figure 1. Map view showing areal sweep problem in inverted 5-spot injector-centered pattern
PO Box 2230 • Keller, Texas 76244-2230 • 817.431.6336 (office) • 817.431.6337 (fax)
www.eclipseoilrecovery.com
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Injector
Producer
Producer
By-passed oil
By-passed oil
By-passed oil
By-passed oil
Figure 2. Cross-sectional view showing vertical sweep problem
Significant variation in reservoir permeability causes injected water or CO2 to disproportionately
sweep only the highly permeable rock, and by-pass the large volumes of oil that are stored in the lower
permeability areas of the reservoir. These conduits or “short-circuits” can sabotage even the bestplanned project, and are the primary reasons why most waterfloods fail to boost total recovery, at best,
beyond only 35% of OOIP. Injected fluids can also breakthrough prematurely at producing wells if the
reservoir contains thick, high viscosity oil. If the Injected water has a much higher mobility and much
lower viscosity than the oil (i.e. poor mobility ratio), then it is more likely to “finger” through the oil instead
of achieving the more desirable “piston-like” displacement.
Eclipse provides polymer gel technology designed to prevent premature breakthrough in new
floods and correct those types of problems that already exist in mature floods. Depending on the
situation, sweep problems may be avoided or corrected by using relatively small gel volumes, or very
large volumes that penetrate deep into the reservoir. When properly placed, these gels reduce the
permeability and flow capacity of the high permeability rock, and subsequently force more of the injection
fluid into smaller oil-bearing pores spaces. As these gels flow into the reservoir, they displace more of
the oil that they contact. The net effect is to make the reservoir appear to be more uniform than it really
is, to the injected fluids, which ultimately leads to better fluid distribution and sweep efficiency.
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Ultimately, the economic life of the project is lengthened, and more oil is recovered faster, with less water
injected and produced. Successful projects recover more oil than could otherwise be recovered by
waterflooding or CO2 flooding alone, and they maintain higher oil producing rates, higher oil-cuts, and
lower WOR/GOR. Candidate floods may exhibit some or all of the following characteristics, which may
be “red flags” indicating that sweep efficiency could be improved by the proper application of polymer gel
technology
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high permeability variation (evidence of fractures and/or high permeability matrix
“streaks”)
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thick viscous oil (adverse mobility ratio)
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high injection rates at low pressure
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evidence of water/CO2 breakthrough at producing wells
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evidence of direct injector to producer communication
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injection profiles showing poor vertical fluid distribution
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high WOR and low oil cut percentage at producers
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good primary recovery and poor secondary/tertiary recovery
An overriding requirement is that there must be a sufficient amount of mobile oil that remains in
the reservoir that can be recovered as a result of the work to justify the expense. The technology is
applicable to sandstone and carbonate reservoirs. Positive results may occur relatively fast (days to
weeks) in thinner formations on tighter spacing, or may take longer (weeks to months) in thicker
formations on larger spacing. Very large volumes of incremental oil can be recovered at a very low
finding cost. If you have a flood that might be a candidate for our technology, then please contact
Eclipse for a free evaluation, design and cost-estimate.
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