Polyacrylamide and its derivatives for oil recovery

Figure 2. 
Timeline for the development of Polyacrylamides for Enhanced Oil Recovery.
 
of methods had been developed to prepare PAM and their derivatives: solution 
polymerization,[25, 31-35] micellar emulsion polymerization,[36-39] inverse-emulsion 
and micro-emulsion polymerizations,[40-46] inverse suspension polymerization,[47-49] 
and living polymerization[50-55].
When injecting water flooding, they may go through channels or fractures with 
high permeability hence reduce the oil recovery efficiency. With gel treatment, the high 
permeable zone can be sealed and the pressure in the unswept area will be improved. 
Therefore the displacing fluid can enter the area with original low permeability hence 
render the profile control.
On the base of the abovementioned polymers, the introduction of a number of 
crosslinkers brought surprisingly extended effects and a mass of crosslinking systems 
were put into field applications[56, 57]. Linear polyacrylamide or modified 
polyacrylamide which can be cross-linked in present of organic, inorganic and metal ion 
cross-linkers has become one of the most significant hydrogel system in EOR. Base on 
different manufacturing methodologies, hydrogels with different chemical properties, 
physical properties and various particle size can be utilized in a number of areas with 
different porosity and permeability. For example, bulk gel or larger particle gel can seal 

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larger channel, while small particle can go through low permeability area and plug the 
tiny holes; gelation system with good chemical stability and can be applied in high 
temperature reservoir; hydrogel with special functional groups could have unusual 
properties such as tolerance to salt, base or acid. Thereby to choose a proper synthesis 
methodology and copolymerized monomer is crucial for the engineers to apply into a 
characteristic situation and render an effective profile control. 
This paper reviews the PAM based polymers and hydrogels utilized in EOR, 
including the synthesis methodologies, structure and properties of the products as well as 
their real application in oil field, aiming at drawing more attention of chemists to this 
surging area of interest so that more advanced products could be developed to meet the 
tremendous demands for oil industry. In addition, polymers for EOR have been 
intensively applied in China and a lot of publications are in Chinese, and this paper will 
also benefit those who are not familiar with Chinese language.