Polyacrylamide and its derivatives for oil recovery

KEYWORDS: 
crosslinking; microgels; stimuli-sensitive polymers; solvent in solvent 
suspension polymerization; polyacrylamide
INTRODUCTION 
Crude oil is an internationally important commodity resource for energy and 
chemical industries. After primary and secondary flooding of the formation, more than 
two thirds of the resource still remain in the reservoir
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. In these tertiary reservoirs, direct 
water or polymer-assisted flooding recovery become inefficient for displacing oil due to 
pore size heterogeneity of the geologic formations. The flooding agent, e.g., water, 
prefers paths of lowest flow resistance. Wider pore channels provide less shear resistance 
compared to narrow pores of higher resistance flow. Preferential flow in previously 
swept, larger pores bypasses low permeability zone leading to excess water production, 
i.e., mostly flooding fluid and less of the desired oil product.
Polymer gels can be cost-effective methods to improve sweep efficiency and 
reduce excess water production for an enhanced oil recovery (EOR).
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Polymer gel 

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treatments of injection wells are being developed to preferentially limit flooding flow 
through larger pore conduit zones. When gels carried by flooding fluid are injected into 
reservoir, the gel particles are prone to enter channels or fractures with lowest resistance 
pressure. Gels may then expand, aggregate or occlude the region to affect the flow 
resistance. If conduit channels are occluded, flooding flow is shifted to new, oil bearing 
areas in the reservoir so more of the remaining oil can be extracted. 
Two types of gels are currently applied in controlling conformance,
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in-situ 
crosslinking gels
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and preformed particle gels (PPGs).
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For in-situ crosslinking gels, 
a mixture of polymers and crosslinking reagents are injected into a target formation to 
polymerize at reservoir temperature to form the ‘in-situ gel’ that is intended to fully or