sulfide is corrosive in nature, which causes leaks or ruptures in pipelines; increases
the potential of environment damage in a remote location and negatively impacts
the facility integrity. Also, the sulfide production can arise abiotically by thermogeochemical processes, but water injection induces the souring significantly by
increased SRB activity. The distinguishing character between this biological and
non-biological sulfide production can be identified by isotope signature analysis of
the ratio of
34
S to
32
S (Frazer and Bolling 1991).
6.3.1 Souring Control by Traditional Methods
Prevention of souring can be done by choosing suitable make-up water sources
without sulfate, but this is generally not possible as oil companies have to depend on
the nearby water source. Additionally, as a prevention measure the sulfate contained
in the injection water can be physically removed by nanomembrane filtration or by
reverse osmosis (Robinson et al. 2010). This protective control technology has
earlier been adopted by some of the North Sea oilfield platforms (McElhiney and
Davis 2002; Odgen et al. 2008). However, the drawback of this technology is the
high cost of installation and maintenance of the filtration system. Therefore, commonly used methods are the application of a chemical to terminate sulfate reduction
or removal of sulfide from injection water. Chemical sulfide scavenger involves
triazines, sodium hydroxide, aldehyde, metal oxides, and nitrite (Vance and
Thrasher 2005). These chemical treatment removes sulfide from the downstream
operation, but are unable to shortfalls of inhibiting sulfide production at the NIWR.
The biocide injection process is regularly followed in the oil industry. Regular
treatment of injection and produced water inhibits a broad spectrum of the attack
on the particular microbial community. However, repeated dosing of biocide
develops the biocide resistance community and therefore alternate injection
strategies are proposed (Telang et al. 1998).
Depending on their function these industrial biocides are broadly divided into two
categories: oxidizing and non-oxidizing biocide. Oxidizing biocides are ozone and
chlorine; these biocides are reactive with microbes, organic matter, solids, and
pipeline material. Non-oxidizing biocides are tetrakis hydroxymethyl phosphonium
sulfate (THPS), glutaraldehyde (Glut), acrolein, bronopol, and quaternary ammonium salts (Fig. 6.1).
Glut is the second most used biocide in oilfields after the THPS. The use of Glut
has found to develop resistance in microbes; therefore, alternation of dosage of
biocide has been used to prevent such occurrence (Gieg et al. 2011). Two reactive
terminal aldehyde group of Glut cross link amino and sulfhydryl group of proteins
and nucleic acids. Quaternary ammonium compounds such as benzalkonium chloride (BAC) work as surfactant, reacting with the cell membrane and rupturing
it. THPS is a biodegradable and less toxic compound (Downward et al. 1997) and
also dissolves ferrous sulfide precipitation. The mechanism of THPS action is still
unknown. Bronopol is an alcoholic compound and inactivates the sulfhydryl group
containing protein via the free radical of electron deficient bromine atom (Legin
120
G. Prajapat et al.
the potential of environment damage in a remote location and negatively impacts
the facility integrity. Also, the sulfide production can arise abiotically by thermogeochemical processes, but water injection induces the souring significantly by
increased SRB activity. The distinguishing character between this biological and
non-biological sulfide production can be identified by isotope signature analysis of
the ratio of
34
S to
32
S (Frazer and Bolling 1991).
6.3.1 Souring Control by Traditional Methods
Prevention of souring can be done by choosing suitable make-up water sources
without sulfate, but this is generally not possible as oil companies have to depend on
the nearby water source. Additionally, as a prevention measure the sulfate contained
in the injection water can be physically removed by nanomembrane filtration or by
reverse osmosis (Robinson et al. 2010). This protective control technology has
earlier been adopted by some of the North Sea oilfield platforms (McElhiney and
Davis 2002; Odgen et al. 2008). However, the drawback of this technology is the
high cost of installation and maintenance of the filtration system. Therefore, commonly used methods are the application of a chemical to terminate sulfate reduction
or removal of sulfide from injection water. Chemical sulfide scavenger involves
triazines, sodium hydroxide, aldehyde, metal oxides, and nitrite (Vance and
Thrasher 2005). These chemical treatment removes sulfide from the downstream
operation, but are unable to shortfalls of inhibiting sulfide production at the NIWR.
The biocide injection process is regularly followed in the oil industry. Regular
treatment of injection and produced water inhibits a broad spectrum of the attack
on the particular microbial community. However, repeated dosing of biocide
develops the biocide resistance community and therefore alternate injection
strategies are proposed (Telang et al. 1998).
Depending on their function these industrial biocides are broadly divided into two
categories: oxidizing and non-oxidizing biocide. Oxidizing biocides are ozone and
chlorine; these biocides are reactive with microbes, organic matter, solids, and
pipeline material. Non-oxidizing biocides are tetrakis hydroxymethyl phosphonium
sulfate (THPS), glutaraldehyde (Glut), acrolein, bronopol, and quaternary ammonium salts (Fig. 6.1).
Glut is the second most used biocide in oilfields after the THPS. The use of Glut
has found to develop resistance in microbes; therefore, alternation of dosage of
biocide has been used to prevent such occurrence (Gieg et al. 2011). Two reactive
terminal aldehyde group of Glut cross link amino and sulfhydryl group of proteins
and nucleic acids. Quaternary ammonium compounds such as benzalkonium chloride (BAC) work as surfactant, reacting with the cell membrane and rupturing
it. THPS is a biodegradable and less toxic compound (Downward et al. 1997) and
also dissolves ferrous sulfide precipitation. The mechanism of THPS action is still
unknown. Bronopol is an alcoholic compound and inactivates the sulfhydryl group
containing protein via the free radical of electron deficient bromine atom (Legin
120
G. Prajapat et al.