Polyacrylamide and its derivatives for oil recovery

Figure 12. 
Mechanism of KYPAM-PEI crosslinking gelation reaction.
 

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50 
has higher threshold pressure and strength and stronger washing resistance than 
phenolic/KYPAM plugging agents. 
Due to cost and performance considerations, PEI has found use in forming gels 
with mixtures of AM, AMPS and N,N-dimethyl acrylamideco-polymers [275] as well as 
simple PAM.[276] PEI-based gel systems have been used in various water shut-off lab 
evaluation where it has found good success.[245, 265, 277-287] Hardy[288] has 
described a co-polymers (PAtBA) of acrylamide and t-butyl acrylate, using PEI as the 
cross-linker. He used the gel in Ekofisk oilfield, Norwegian Sector of the North Sea. For 
the treatment, the 7%PAtBA was mixed in the platform injection water tanks first, then 
the PEI was blended with the polymer solution, finally pumped the mixture down hole 
through coil tubing with the injection rate at 12.58m
3
/min. The detailed results are in 
Table 2. 
Table 2 
Production of the B-21A Well: Immediately before and after the organic crosslinking 
polymer treatment.[288] 
Interval 
Pre-Job 
Post-Job 
10715 to 10720 ft 
27.6% 
16.67% 
10760 to 10765 ft 
13.8% 
12.5% 
10808 to 10813 ft 
13.8% 
12.5% 
10855 to 10865 ft 
20.7% 
26.25% 
10904 to 10914 ft 
13.8% 
15.41% 
10953 to 10963 ft 
10.35% 
0% 
11003 to 11013 ft 
UNK
a
16.67% 
11040 to 11045 ft 
UNK
a
UNK
b
11053 to 11063 ft 
UNK
a
UNK
b
UNK
b
11185 to 11195 ft 
0%
b
UNK
b
a.
Not accessible to the logging tool due to the obstruction. 
b.
Assumed to be 0% due to the CaCO3/cement plug. 

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51 
The technology using organic cross-linker is considered mature and many field 
application examples of organically cross-linked PAM flooding polymers can be 
found.[258, 286, 288, 289]