Chemistry Reference
In-Depth Information
5.7.1 Drilling Additives
With the increasing concerns on the environmental impact of oil-based drilling
fluids in oil-field applications, the water-based drilling additive systems have been
extensively used as shale inhibition, viscosity building, and filtration control for
enhancing oil recovery [
211
,
212
]. As the most important environmentally friendly
polymers, the modified natural polymers show great potentials in oil-field applica-
tion due to their renewable, low cost, nontoxicity, and biodegradability [
213
].
Currently, the modified cellulose such as carboxymethylcellulose, polyanionic
cellulose, and cellulose graft copolymers was mainly focused and frequently
used. Recently, with the increasing concerns on plant gum, gum-based polymers
begin to be concerned because they have excellent viscosity and can be easily
modified to form new materials. XG or its graft polymer was considered as a
potential drilling additive because it has anionic characteristic with side-chain
structure, higher molecular weight, excellent viscosity, good shear stability, and
salt-resistance capability [
214
,
215
].
5.7.2 Thickener
Currently, the commercial thickeners mainly include four categories: inorganic
thickeners, cellulose, polyacrylate, and associative polyurethane thickener. The
cellulose thickener has long usage history and various types, such as methylcellu-
lose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl
cellulose. With the progress of modern industry, the development of novel thicker
with higher thickening efficiency and nontoxic characteristic becomes the subject
of great interest. As described above, the aqueous solution of almost all the gums
has gained great viscosity due to the interactions between polymer chains, and so
gums are the important thickener in manufacture, distribution, storage, and con-
sumption of water-based products, particularly formulations of surface coatings,
drugs, cosmetics, and foods [
216
,
217
]. Compared with the raw gums, the gum-g-
copolymer usually showed higher viscosity due to the change of molecular weight,
chain-chain interaction, and structure charges. Nickzare et al. modified acacia gum
by its graft copolymerization with acrylic monomers for a thickening purpose, and
it was found that the thickening properties were highly improved to form non-
Newtonian fluids in water at concentrations below 2 % [
218
].
5.7.3 Adsorption of Toxic Heavy Metals
As discussed above, the gum-g-copolymer has strong complexing capability, and so
it showed great prospect in the adsorption of toxic heavy metals. Sharma and Lalita
[
130
] prepared GG-g-PNVP polymer and used for the sorption of Fe
2+
and Cr
6+
ions. It was found that the adsorption amount increased with increasing percent
