Polyacrylamide and its derivatives for oil recovery

2.3
 
Comb-type Polyacrylamides 
In fresh water, the groups of -COOH or –COONa in traditional PAMs produce 
exclusion effect causing polymer chain extension so that the polymer solution viscosity 
increases. While in brine, the interaction between the charges in polymer chain and ions 
in solution will lead to polymer chain curling or collapse, decreasing the molecular size 
in solution. Comb-type polymers based on PAM were designed to solve this problem.[23] 
The introduction of a hindering structure generated a random coil configuration that does 
not fully collapse under a high salinity environment. The salt resistant comb polymers 

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26 
generally contained both hydrophilic and hydrophobic groups as side chains.[127, 128] 
Due to the inter-exclusion effects between these two groups, polymer chain were 
stretched and collapsing phenomenon will be decreased inter and intra polymer chains, 
hence the polymer chains arrange as comb type in aqueous. Comb polymers are 
characterized by their high viscoelasticity and good salinity resistance. Consequently, an 
increased EOR efficiency in brine can be achieved.[129] 
Luo, et al.[130] developed a comb-type, salt-tolerant polymer (KYPAM) for EOR 
(see Figure 3), manufactured by PetroChina, 1999. Several tests were made in 
comparison to the products MO-4000 from Mitsubishi, Japan and HPAMS DQ2B838 of 
PetroChina Company, China in a lab scale evaluation. The viscosity of 1000 mg/L (0.1 
wt.%) KYPAM solutions in fresh water or brines with 1000 to 19.334 g/L NaCl under 
different temperatures (45, 70, and 80 °C) was 30 to 40% higher than the other 
comparison sample solutions of similar concentration. In the core flooding experiment at 
70 °C, the EOR and the retardation factor (RF) and relative response factor (RRF) 
values[125] were higher for KYPAM solution than a comparative product HPAM 1285 
from British Colloid.[131]
Early KYPAM was described as a copolymer of monomer A and monomer B 
where A contains one or several unsaturated sites and is a water soluble monomer, while 
B was characterized by the following structure:[23]
R
1
R
2
R
3
R
4
A