Polyacrylamide and its derivatives for oil recovery

Figure 11. 
The Reaction Mechanism Between PAM and PEI. [267]
 

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48 
Baojun Bai, et al. reported a series of preformed particle gel (PPG) which is a 
particle superabsorbent cross-linked polymer gel.[179-184] It can swell up to 200 times 
its original size and showed elastic deformation ability. The strength and swelling 
capacity of it is controllable by adding different amount of crosslinker and other addictive 
agent. It is not sensitive to reservoir minerals and formation water salinity. This cut 
particle gel with certain size comes from bulk gel synthesized in solution with methylene-
bis-acrylamide (MBAM) as crosslinker, one or several of acrylamide, acrylic acid, 2-
acrylamido-2methylpropane sulfonic acid and other vinyl functional monomers as co-
monomers. The organic cross-linkers with multiple telechelic double bonds were 
employed to realize 3-D gelation structure. After dried, cut or crushed, the particle gel 
was produced from a bulk of large gel.[179, 269] When blocked by rocks in reservoir, it 
can go through the fracture via deformation. Yet the salinity can decrease the swell 
property of this gel, it can promote its strength. Furthermore, some PPGs perform stable 
under as high temperature as 120 ̊C.[177, 180, 181] PPG treatment has been applied in 
four injection wells located in the north lF Lamadian, Daqing oilfield, China, which is 
sandstone oilfield with thick net zones. PPG suspension with concentrations of 2000-
2500 mg/L and particle sizes of 0.06-3.0mm was injected into reservoir (water cut of 
95.4% before treatment). This resulted in an oil increase of 34.8t/day and average water 
cut decrease of 0.94% within 10 months after treatments.[182] So far, the PPGs have 
been used successfully as conformance control agents in more than 5000 wells to help 
control both water and CO
2
production.[182, 183, 270] Transport mechanism through 
porous media of PPG was investigated from microscopic and macroscopic scale.[181, 
184] Other evaluation information can be reviewed in other lab test.[271, 272] 

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49 
Based on the solid background of PPG, Bai proposed a kind of thermo-dissoluble 
polyacrylamide (TDP) crosslinked gel which can be used for in-depth-mobility 
control.[273] TDP was prepared in 
solution 
free radical 
polymerization and two crosslinkers 
were adopted
to control the strength and effective time
, N,N’-methylenebisacrylamide (MBAA)
worked as stable crosslinker,
and polyethylene glycol 
diacrylate 
(PEGDA) 
served as the weak 
one. After drying and cutting, bulk gel were crushed into particle gel. This particle gels 
were firstly injected into the fractures or kind of features acting as plugging agent and 
then dissolves into polymer solution at a designated time stimulated by reservoir 
temperature. The formed polymer solution then seeped into the depth and behaved as a 
mobility control agent.
Zhou et al.[274] developed a plugging agent employing KYPAM and 
polyethyleneimine through a crosslinking reaction between 

NH

of (

CH
2
-CH
2
-NH

)
n
and the –CONH
2 
of KYPAM (see Figure 12). The resulting polymer had a molecular 
weight of 8x10
6
Da that can be used in reservoir temperatures from to 80 to 110°C and 
salinity ≤80g/L NaCl + 1.2g/L CaCl
2
. Additionally, the KYPAM cross-linked polymer
C
H
3
CH CH CH
2
C
N
H
2
O
R'
+
H
2
C
NH
CH
2
CH
2
NH
CH
2
CH
2
NH
C
H
3
CH CH CH
2
C
O
R'
N
CH
2
H
2
C
CH
2
CH
2
NH CH
2
CH
2
NH
+
NH
3