Polyacrylamide and its derivatives for oil recovery

4. Conclusions 
This paper mainly reviewed the function of polyacrylamide and its derivative 
products in EOR through two main aspects: one is the viscosity thickener as the polymer 
flooding agent; another is they can act as sealing agent via forming cross-linking 
structure in present of cross-linkers to render conformance control. This review clearly 
indicates the structure of the different polyacrylamide and their derivatives as well as the 
according properties of them. In particular, this review elaborates synthesis methods of 
each kind polymer and gives their application in detailed.
For the polyacyrlamides working as the displacing agent, they work as a basic 
thickening agent in polymer flooding solution. As the reservoir environment turning 
harsher and harsher, kinds of modification method came up aiming at resist the high 
temperature, high salinity, and poor pH. According to Table 4, there is a number of 
typically functional monomer can be employed to modify the polyacrylamide chain 
hence increase the solution viscosity facing different reservoir. Among the 
polyacrylamides, high molecular weight PAM/HPAM is of the longest history no matter 
in preparation or in field application. Then, through introducing hydrophobical side or 
ionic side, researchers found same viscosity increasing phenomenon happened in not high 
molecular weight PAM. A lot of research has been done in these two kinds of 
polyacrylamides and successful filed application can give us pragmatic instruction.

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Gradually, research tried to combine both the ionic and hydrophobical modification and 
get some progress but less practical field application.
For the polyacrylamide effect as sealing gel, different polyacrylamides place an 
important part in sealing various areas with different permeability and environment 
conditions. Generally, large bulk gels are synthesis by solution method and using metal 
ion or organic cross-linker to achieve 3-D network structure. They will work to seal the 
large fracture or large channel so that change the direction of the flooding solution and 
harvest the oil from the production well. While, the large gel cannot penetrate the thief 
areas with tiny hole size. Hence micro-gel will work for this. Usually, micro-gel come 
from emulsion/micro-emulsion polymerization so that their size can be well controlled by 
virtue of adjusting the composition of pre-emulsion and reaction shearing rate. They can 
go through narrow pore and channel to reach the target site and seal it thereby rendering 
in-depth profile control. PPG come from cutting the bulk 3-D gel can also do this work 
only through fine granding Hybrid material is a promising direction in PAMs Gel 
preparation. It holds attractions however not too much real work has been done. Table 5 
gives a summery about different kinds of cross-linkers and their properties. Selection of 
a given gelant greatly depends on the practical temperature, salinity, and hardness of the 
reservoir as well as the condition of the solutions (brine, water, or sea water). 
The demanding, hostile field environments such as high temperature and high 
water salinity and hardness in oil recovery has required unique polymers with new 
structures. Polymer design developments include non-ionic monomers were more 
resistant to chemical alternation, and the neighboring acrylamide moieties also stabilized; 
anionic monomersproduced polymers that were more resistant to cation shielding and 

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self-precipitation; hydrophobic monomersendowed intermolecular association which is 
favorable for efficient viscosity enhancement[316]; long polymer chains of high 
molecular weight were used with engineered side chains as “arms” to affect solution 
viscosity; high molecular weight linear PAM chains were used as a backbone to proffer 
hydrophobic side chains with intermolecular association effects. .Lastly, it appears that 
environmentally friendly methods, such as ScCO
2
polymerizations, and EOR products 
should be developed whenever accessing natural resources, to be ever mindful of 
environmental protection.

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