Lecture 13 Flashcards
What kind of nitrate reduction pathways are indicated by the presence of:
- nrf genes
- nirS/nirK genes
nrf genes reduce NO3- to NH3. (DNRA)
nirS/nirK genes reduce NO3- to NO. (Denitrification)
Why would a sulfate reducing microbe have a Nrf gene?
By reducing nitrite it detoxifies its environment, preventing the inhibition of dissimilitory sulfite reductase.
What are the steps in a serum bottle test when determining the efficiency of a biocide/ nitrate addition against souring?
- Add and electron donor (crude oil/ VFA) and a sulfate
- Measure sulfate loss or sulfide production.
- When half of the sulfate is used assume the cells are in an exponential growth phase. At this point add the treatment.
- Determine if/ to what extent sulfate reduction has stopped.
Draw a schematic of a sand packed column system. How do you know if sulfate reduction is occurring in these systems and what environment are they meant to emulate?
- pg 4
- Black sand colouration indicates sulfate reduction
- meant to emulate a reservoir condition
What is one hypothesis to explain why nitrate treatments are more effective in higher temperature reservoirs?
That nitrite accumulates better at temperatures greater than 50 C
At what temperature is it likely to find the following groups being major members of a bacterial community?
- Geobacillus
- Petrobacter
- Pseudomonas
- Thauera
40-45 C : Theuera, Pseudomonas
50-70 C : Geobacillus, Petrobacter
What does FPSO stand for?
Floating production storage & offloading
How does the zonation model explain sulfide being produced when in the presence of nitrate reducers?
Since NRM become active at a lower temperature than SRM, (30 vs 55 C) most of the nitrite will be produced right at the injection well and have a hard time traveling through the medium toward the high temperature areas where SRM can exist without having to worry about nitrite toxicity.
