Lecture 5: Life in rocks Flashcards
souring of oil wells
1926
- known for many years that micro-organisms cause souring
- microbial induced corrosion is a major problem
- microbes produce acid to go through steel
microbes & fuel
microbes can degrade fuels
- for clean up? –> possible ecosystem service
- > can be a bad thing aeroplane fuel tanks
example of microbe that leads to oil souring
Archaeoglobus fulgidus
– chemoautotroph
problems with studying life in rocks
- Access
- – extremely limited
- – many organisms are obligate piezophiles
- contamination
- identification
- – many bacteria ‘shrink’ when starved of nutrients., can be tiny, hard to find
- biology
- – is an individual organism millions of years old or is there a slowly growing population at depth? / different time scale?
piezophiles
pressure lovers
problems faced by organisms living within rocks
- extremes of heat and pressure
- space (must be enough room for them to live)
- nutrients and energy source
- access –> how do they get there?
confined subsurface microbial communities in Cretaceous rock:
KRUMHOLZ ET AL 1997
- drill into side of volcanoe
- erupts, sterilises everything
- angled borehole unsuccessful but vertical a little further away was
- drill down 300m obtained rock cores
- fluorescent dyes for contamination
- foil w radioactive sulphate used
- sample analysed
- spikes in bio activity where sandstone and shale meet as where organic material is
drilling into rocks: what do you need
drilling fluid
- contain contaminants, must use tracer to determine if recovered material is contaminated
- tracers =
- –fluorescent dyes
- – fluorescent microspheres
- – volatile perfluorocarbons
detection of biological activity in rock cores
- rock cores are sectioned and overlaid with a foil containing radioactively labelled sulphate
- biological activity reduces sulphate to sulphide (sulphates wash off)
why peaks in biological activity where sandstone and shale meet
- shale rich in organic material but too compact for life
- sandstone larger pore size filled w water, but lack organic nutrients
shale and sandstone what happens to radioactive labelled sulphate foil
it is reduced to sulphide and acetate production (acetate is important substrate for microbial growth)
acetate and microbes
important substrate for growth
drilling bore holes expenses
deeper u go, more expensive it is. so how do we get around this?
alternatives to drilling multiple bore holes
- drill one, let it fill w water, lower down substrate to certain depth
- MULTILEVEL SAMPLER
- measure the microbes grown on those substrates
- measure conc of microbes at diff depths
- 16S rRNA gene sequencing used
- careful to not ruin rock stratification
- KOVACIK ET AL 2006 used one
microbial activity in oil reservoirs:
- sandstone, below = water saturated, top = oil water contact
- water supplies nutrients
- near oil-water contact, microbes skew oil material, as oil degraded
