American Oil and Gas Reporter - June 2014 - 103

SpecialReport: Artificial Lift Technology
Mcf/bbl. The incremental oil produced
from this work is estimated at 770,000
barrels of oil at a cost of $1.88 a barrel.
Further improvement and flattening
of the GOR displayed in Figure 3 has
been seen as ongoing gel treatments were
performed for a 33 percent decrease in
GOR. The project area has had 29 polymer
treatments totaling more than 384,600
barrels of gel. The total cost of polymer
gel work to date is $0.39 per barrel of oil
produced. These economics neglect the
deferred production in P1 and time value
of money.
In one of the P1 patterns requiring
conformance, the GOR peaked at more
than 50 Mcf/bbl before the treatment was
FIGURE 5
Well 34-6 Log and Injection Profiles

implemented. The 11,221-barrel treatment
reduced GOR for 18 months and produced
80,000 barrels of incremental oil at $1.27
a barrel.
During the P1 treatments, many interwell connections were confirmed by the
presence of polymer in the surrounding
production wells. The lost/deferred production resulting from shutting in these
producers after polymer breakthrough,
and pump problems created when those
wells were brought back on line, are not
quantified by these economics. The channels identified while treating P1 are shown
on the map of the center of P1 (Figure
4), with the dotted lines representing the
channels.
Polymer breakthrough created a virtual
spider web on the map, highlighting the
severity of the channeling issues and
demonstrating that the channels did not
have a preferred orientation.
P2 Strategy
The P2 strategy consisted of implementing all the polymer treatments prior
to CO2 flooding. It was based on findings
from the economic success of P1 and
understanding that P2's flooding hurdles
would be the same.
Treatment economics could be improved by reducing production well downtime and eliminating any possible CO2

gel contamination. Past injection profiles,
step-rate tests and injection rates defined
candidate wells. These criteria also were
used in P1 candidate selection. If these
candidates were left untreated, these problems would almost certainly result in
rapid CO2 breakthrough.
Figure 5 shows the log and injection
profiles from the P1 pattern injector 346. The first two profiles (depicted on a 0
to 100 scale) show injection before polymer gel treatment, and the second two
show injection after treatment.
One of the major improvements was
reducing the zone taking 29-37 percent
of injection down to 13-19 percent, although the entire well has been improved.
Production rates and any available production profiles were analyzed to identify
potential problem wells. Because of the
amount and severity of the issues, the
final approach was to treat all wells that
would take polymer as well as any wells
that acid stimulated outside expected
rates and pressures.
The project area received 30 polymer
gel treatments totaling more than 500,000
barrels of gel, all of which was pumped
prior to injecting CO2. Figure 6 shows
the manifold production rates for P2. Oil
production started quicker and GOR has
exhibited a more gradual increase, compared with P1 in Figure 3. It must be

FIGURE 6
Platform 2 Manifold Production
100

Gas-to-Oil Ration (Mcf/bbl)

Total project polymer cost:
$1.50 per barrel oil (to date)
Projected polymer cost:
$0.38 per barrel oil

* Blue is Water
* Red is CO2

10
GOR (scf/bbl)
Oil (bbls)

0.1
1,000
Jun 2012

10,000
Jul 2012

100,000
Sep 2012

1,000,000
Apr 2013

Cumulative Oil (bbl)

JUNE 2014 103

American Oil and Gas Reporter - June 2014

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