scleroglucan, welan gum, schizophyllan, mushroom polysaccharide, cellulose, and
lignin. Biopolymers have added advantage over the synthetic polymer like biopolymer has more rigidity, increased viscosity at higher temperature, superior tolerance
to salts/temperature, outstanding thickening capability and stability in harsh condition of reservoirs. Along with these mentioned benefits biopolymer also has
limitations like well plugging due to cell debris, bacterial sensitivity, and poor
filterability. Other than these, nano-celluloses based nanofluids have better capability to involve in oil displacement (Pu et al. 2018). During the selection of polymer/
biopolymer different rheological properties to be tested at each field condition.
Xanthan is a bacterial polysaccharide and has rigid polysaccharide chains, thus
less sensitive to mechanical shear, elevated salinity, and divalent ion concentration.
Demerits of using xanthan gum are its high susceptibility to biodegradation and high
risk of plugging in rock pores (Pu et al. 2018; Gbadamosi et al. 2019). Other
biopolymers such as scleroglucan, produced by fermentation of a plant pathogen
fungus (genus Sclerotium) are also been proposed as EOR agent. This is a good
substitution of HPAM due to its good solubility and eco-friendly nature. This
biopolymer is durable to various pH and high mineralization. Scleroglucan has an
excellent viscosifying ability due to its high molecular weight and rigid structure.
Some demerits of scleroglucan are its cost, ease of biodegradation, and poor
filterability.
Hydroxymethycellulose (HEC) is a derivative of amorphous cellulose and
non-ionic in nature. HEC has high molecular mass, rigid backbone structure,
cheap in cost, non-toxic, and eco-friendly features suitable for uses as an ideal
biopolymer. HEC is a shear resistant, salinity durable, and temperature tolerant
biopolymer. HEC has some drawbacks like oxidation, biodegradation, and enzymatic degradation.
6.6
Biotechnological Upgradation of Produced Oil
Biotechnological upgradation of produced oil is industrial interest. This is due to the
increase in concentration of sulfur in produced oil. Increased sulfur content in oil is a
major environment concern. Biodesulfurization is a biological method for the
removal of sulfur content in produced oil. Biodesulfurization was initially developed
for the removal of inorganic (pyrite) and organic sulfur from coal by
microorganisms. In petroleum, organic sulfur removal in transportation fuels is
also a major concern. In crude oil, benzothiophene (BT) and dibenzothiophene
(DBTs) are two main organosulfur compounds that are recalcitrance to removal by
refinery process (e.g., hydrodesulfurization). DBT is the model compound for
biodesulfurization research. Many microbes were investigated for their ability to
utilize DBT as a sole sulfur source. Anaerobic desulfurization is less investigated,
thus lack of anaerobic biochemistry and genetics of the desulfurization process are a
major hurdle for commercial desulfurization process development. In the
biodesulfurization process, there is low energy requirement, less generation of
unwanted products, and low emission of sulfur containing compounds compared
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lignin. Biopolymers have added advantage over the synthetic polymer like biopolymer has more rigidity, increased viscosity at higher temperature, superior tolerance
to salts/temperature, outstanding thickening capability and stability in harsh condition of reservoirs. Along with these mentioned benefits biopolymer also has
limitations like well plugging due to cell debris, bacterial sensitivity, and poor
filterability. Other than these, nano-celluloses based nanofluids have better capability to involve in oil displacement (Pu et al. 2018). During the selection of polymer/
biopolymer different rheological properties to be tested at each field condition.
Xanthan is a bacterial polysaccharide and has rigid polysaccharide chains, thus
less sensitive to mechanical shear, elevated salinity, and divalent ion concentration.
Demerits of using xanthan gum are its high susceptibility to biodegradation and high
risk of plugging in rock pores (Pu et al. 2018; Gbadamosi et al. 2019). Other
biopolymers such as scleroglucan, produced by fermentation of a plant pathogen
fungus (genus Sclerotium) are also been proposed as EOR agent. This is a good
substitution of HPAM due to its good solubility and eco-friendly nature. This
biopolymer is durable to various pH and high mineralization. Scleroglucan has an
excellent viscosifying ability due to its high molecular weight and rigid structure.
Some demerits of scleroglucan are its cost, ease of biodegradation, and poor
filterability.
Hydroxymethycellulose (HEC) is a derivative of amorphous cellulose and
non-ionic in nature. HEC has high molecular mass, rigid backbone structure,
cheap in cost, non-toxic, and eco-friendly features suitable for uses as an ideal
biopolymer. HEC is a shear resistant, salinity durable, and temperature tolerant
biopolymer. HEC has some drawbacks like oxidation, biodegradation, and enzymatic degradation.
6.6
Biotechnological Upgradation of Produced Oil
Biotechnological upgradation of produced oil is industrial interest. This is due to the
increase in concentration of sulfur in produced oil. Increased sulfur content in oil is a
major environment concern. Biodesulfurization is a biological method for the
removal of sulfur content in produced oil. Biodesulfurization was initially developed
for the removal of inorganic (pyrite) and organic sulfur from coal by
microorganisms. In petroleum, organic sulfur removal in transportation fuels is
also a major concern. In crude oil, benzothiophene (BT) and dibenzothiophene
(DBTs) are two main organosulfur compounds that are recalcitrance to removal by
refinery process (e.g., hydrodesulfurization). DBT is the model compound for
biodesulfurization research. Many microbes were investigated for their ability to
utilize DBT as a sole sulfur source. Anaerobic desulfurization is less investigated,
thus lack of anaerobic biochemistry and genetics of the desulfurization process are a
major hurdle for commercial desulfurization process development. In the
biodesulfurization process, there is low energy requirement, less generation of
unwanted products, and low emission of sulfur containing compounds compared
126
G. Prajapat et al.