Chemistry Reference
In-Depth Information
Table 3.1
Role of different grafted starches in oilfield applications [
118
]
Grafted starch
Application
Starch-g-poly(acrylamide)
1. Controlling filtrate loss for drilling muds
2. Increasing viscosity of drilling muds
3. Modifying viscosity in displacement fluids for
enhanced oil recovery (EOR)
Oxidised starch-g-poly(acrylamide)
Modifying viscosity in displacement fluids for EOR
Soluble starch-g-poly(acrylamide)
Modifying viscosity in displacement fluids for EOR
Starch-g-poly(sulphomethylated
acrylamide)
1. Controlling filtrate loss for drilling muds
2. Increasing viscosity of drilling muds
Pregelatinised starch-g-poly
(acrylonitrile)
Reducing filtrate loss for drilling muds
Starch-graft-copolymer with cationic
allyl monomer
Inhibiting hydration of clay and shale
Starch-graft-copolymer with acrylamide
and vinyl alcohol
1. Controlling filtrate loss for drilling muds
2. Increasing viscosity of drilling muds
[
118
] reviewed the applications of starch and their derivatives in oilfield
applications in China. The role of these polymers in oil drilling is multifaceted
depending on the properties (Table
3.1
). Most of the starch-graft-copolymers have
better resistance to temperature and shear rate than hydrolysed poly(acrylamide)
and have potential application in enhanced oil recovery.
Water-soluble starch-graft-copolymers are mainly used for controlling filtrate
loss for drilling muds, modifying viscosity in displacement fluids and inhibiting the
hydration of clay and shale [
119
,
120
]. It was found that grafted starch could
provide more effective shale inhibition than anionic or non-ionic modified starches,
showing potential as a shale- or clay-hydration inhibitor for oilfields. Acrylamide is
the widely used monomer for this application. Grafting of shear degradable poly
(acrylamide) onto the rigid starch backbone provides fairly shear stable systems.
Monomers such as acrylamide and vinyl alcohol have been grafted onto starch
substrate resulting in non-ionic grafted starches having possible use as drilling mud
additives. A copolymer was synthesised by graft copolymerisation of starch with
acrylamide and 2-acrylamido-2-methylpropanesulfoacid for oil recovery enhance-
ment [
121
]. When using 0.2 % of the grafted starch [S-g-P(AM-
co
-AMPS)] as the
flooding agent, a higher enhanced oil recovery rate was obtained than with hydro-
lytic polyacrylamide (HPAM).
Starch-grafted polyacrylamide copolymers were prepared and their rheological
properties, either in water or in water-based muds, were investigated Eutamene
et al. [
122
]. Compared to the non-modified starch, starch-grafted polyacrylamide
copolymers behaved as shear-thinning and salt resistant, and their rheological
properties are stable with time. The grafted starches as prepared above were also
added to water-based mud and the rheological properties of the resulting muds were
determined under oil-well conditions. Grafted starches, having high AM contents,
were more efficient in decreasing the filtrate volume, and increasing the plastic
viscosity of the muds, when compared to PAC-L, a modified cellulosic polymer
used in the filtration control of most water-based muds.
