6.3
Oil Field Souring
Biogenesis of hydrogen sulfide (H 2 S) by SRB (known as a souring) has a deleterious
effect on the human which could lead to death after inhalation. This anthropogenic
H 2 S generation is not only dominated in the oil industry but also found in paper and
pulp industry, rayon textile production, chemical manufacture, and waste disposal.
Annual cost estimated $90 billion associated with the microbially produced H 2 S in
reservoir and fluids (Gieg et al. 2011). While, injection of water during the secondary
recovery is found to be mostly responsible for souring in oil fields. The probable
reason for such an effect could be the sulfate content in the injection water used by
oil industries. Water sources used for secondary recovery are seawater, municipal
waste water, and the saline aquifer that contain moderate to high sulfate concentration (5–30 mM). In offshore oilfields the seawater are injected which contain high
sulfate concentration of 25–30 mM (Voordouw and Grigoryan 2009). Sulfate
containing water injected in an oil reservoir is conducive for SRB activity in the
reservoir matrix and leads to conversion of sulfate to sulfide. While, injection water
also act as a source of both inoculum and electron acceptor. Therefore, both indigenous and adventitious populations thrive in reservoir rock and are responsible for
reservoir souring. Also, during the secondary oil recovery process, water-flooding
decreases the temperature of the reservoir and also dilutes the harmful petroleum
fluids. These further creates a zone at the near injection wellbore region (NIWR),
making it a suitable condition for boosting microbial growth.
Additionally, in the reservoir, more labile electron donors are present in the form
of simple organic acids (acetate, propionate, butyrate, etc.) at high concentrations as
much as 1500 mgL
À1 (Vance and Thrasher 2005). Besides utilizing these electron
donors, SRB are also capable to utilize diverse aliphatic and aromatic hydrocarbon
(Anderson and Lovley 2000; Annweiler et al. 2000; Abu Laban et al. 2009).
Therefore reservoir conditions provide a limitless carbon and energy supply to
activate microbial population. The composition or quality of injection water is a
key factor to the extent of SRB activity in situ. Produced water re-injection (PWRI)
strategy also provides the soluble oil organics like volatile fatty acids (VFA). VFAs
include acetate, butyrate, and propionate and other organic, for example, lactate.
VFAs are completely oxidized by SRB in CO 2 and incompletely oxidized into
acetate that is excreted into the environment (Widdel and Rabus 2001).
The large quantities of H 2 S generated by SRB cause a variety of problems
(Larsen 2002), such as contamination of crude oil, metal corrosion, and the
precipitation of metal sulfides. The souring in production facilities and the reservoir
leads to additional costs associated with the prevention of operators exposure to
toxic H 2 S, reduced oil–water separator performance, management of iron
sulfide solids, and accumulation of iron sulfide deposits that are responsible for
the enhancement of equipment corrosion and fouling of equipment corrosion
(Vance and Thrasher 2005). Sulfide production has been broadly classified to
have three negative impacts; firstly, the toxicity of sulfide as a concern to the
worker and public health. Secondly, sulfide production decreases the oil quality,
and, therefore, sulfur content must be lowered by processing facilities. Lastly,
6 Application of Biotechnology in Oil and Gas Industries
119
Oil Field Souring
Biogenesis of hydrogen sulfide (H 2 S) by SRB (known as a souring) has a deleterious
effect on the human which could lead to death after inhalation. This anthropogenic
H 2 S generation is not only dominated in the oil industry but also found in paper and
pulp industry, rayon textile production, chemical manufacture, and waste disposal.
Annual cost estimated $90 billion associated with the microbially produced H 2 S in
reservoir and fluids (Gieg et al. 2011). While, injection of water during the secondary
recovery is found to be mostly responsible for souring in oil fields. The probable
reason for such an effect could be the sulfate content in the injection water used by
oil industries. Water sources used for secondary recovery are seawater, municipal
waste water, and the saline aquifer that contain moderate to high sulfate concentration (5–30 mM). In offshore oilfields the seawater are injected which contain high
sulfate concentration of 25–30 mM (Voordouw and Grigoryan 2009). Sulfate
containing water injected in an oil reservoir is conducive for SRB activity in the
reservoir matrix and leads to conversion of sulfate to sulfide. While, injection water
also act as a source of both inoculum and electron acceptor. Therefore, both indigenous and adventitious populations thrive in reservoir rock and are responsible for
reservoir souring. Also, during the secondary oil recovery process, water-flooding
decreases the temperature of the reservoir and also dilutes the harmful petroleum
fluids. These further creates a zone at the near injection wellbore region (NIWR),
making it a suitable condition for boosting microbial growth.
Additionally, in the reservoir, more labile electron donors are present in the form
of simple organic acids (acetate, propionate, butyrate, etc.) at high concentrations as
much as 1500 mgL
À1 (Vance and Thrasher 2005). Besides utilizing these electron
donors, SRB are also capable to utilize diverse aliphatic and aromatic hydrocarbon
(Anderson and Lovley 2000; Annweiler et al. 2000; Abu Laban et al. 2009).
Therefore reservoir conditions provide a limitless carbon and energy supply to
activate microbial population. The composition or quality of injection water is a
key factor to the extent of SRB activity in situ. Produced water re-injection (PWRI)
strategy also provides the soluble oil organics like volatile fatty acids (VFA). VFAs
include acetate, butyrate, and propionate and other organic, for example, lactate.
VFAs are completely oxidized by SRB in CO 2 and incompletely oxidized into
acetate that is excreted into the environment (Widdel and Rabus 2001).
The large quantities of H 2 S generated by SRB cause a variety of problems
(Larsen 2002), such as contamination of crude oil, metal corrosion, and the
precipitation of metal sulfides. The souring in production facilities and the reservoir
leads to additional costs associated with the prevention of operators exposure to
toxic H 2 S, reduced oil–water separator performance, management of iron
sulfide solids, and accumulation of iron sulfide deposits that are responsible for
the enhancement of equipment corrosion and fouling of equipment corrosion
(Vance and Thrasher 2005). Sulfide production has been broadly classified to
have three negative impacts; firstly, the toxicity of sulfide as a concern to the
worker and public health. Secondly, sulfide production decreases the oil quality,
and, therefore, sulfur content must be lowered by processing facilities. Lastly,
6 Application of Biotechnology in Oil and Gas Industries
119