|Natural gas being wasted in an admittedly cool way (Source)|
In 1938, a Russian scientist by the name of Mogilewskii published a paper describing the use of methane-oxidizing bacteria as a means of prospecting for natural gas fields. Several patents were subsequently issued to oil companies in the 1940s based on this paper and others by American researchers.
The idea is that smaller gaseous hydrocarbons (e.g. methane, propane, butane) tend to escape in small amounts from underground oil and gas deposits and rise to the surface. The continuous seepage of these hydrocarbons through the soil overlying a deposit can lead to the relative enrichment of specialized bacteria capable of using them to acquire energy (via oxidation) and as a carbon source.
Incidentally, in some parts of the world hydrocarbon gases seep to the surface at rates sufficient to fuel persistent natural fires such as Yanar Dag in Azerbaijan, Yanartaş in Turkey, and the cool flame behind the waterfall in New York.
As a positive relationship exists between the number of hydrocarbon-utilizing bacteria and hydrocarbon concentrations in a particular section of soil, collecting soil samples and quantifying these bacteria can provide an indicator of the presence of buried fossil fuels. This approach can also be used to establish the boundaries of a known oil or gas deposit and then prioritize drilling locations within this field. Microbial prospecting tends to be integrated with geological methods and is advantageous because it can reduce the amount of drilling that needs to be done to find exploitable amounts of subterranean oil or gas.
The classic method of characterizing oil- and gas-indicating bacteria involves suspending a soil sample in water and then placing some of the resulting slurry into a liquid growth medium contained within a flask filled with a gaseous hydrocarbon (e.g. methane). The number of hydrocarbon-consuming bacteria in the soil sample can then be estimated by measuring the time required for the hydrocarbon to be consumed.
A newer approach is to quantify or simply look for genes associated with hydrocarbon-utilizing bacteria. For example, the prmA and bmoX genes encode enzymes used by certain bacteria to oxidize propane and butane, respectively. Unlike methane, the natural presence of large amounts of these hydrocarbons is restricted to oil and gas fields, so detection of prmA and bmoX in soil samples can provide a good indicator of these locations.
Chan BJ. 2011. PCR primers for the detection of propane and butane-oxidizing microorganisms. Master's Thesis. [Full text]
Phillips Petroleum Company. 1959. Prospecting for petroleum deposits. US Patent 2880142 [Full text]
Rasheed MA, Hasan SZ, Rao PS, Boruah A, Sudarshan V, Kumar B, Harinarayana T. 2015. Application of geo-microbial prospecting method for finding oil and gas reservoirs. Frontiers of Earth Science 9(1):40-50. [First two pages]
Soli GG. 1957. Microorganisms and geochemical methods of oil prospecting. AAPG Bulletin 41(1):134-140. [First page]
Standard Oil. 1941. Oil prospecting method. US Patent 2234637 [Full text]
Zhang F, She Y, Zheng Y, Zhou Z, Kong S, Hou D. 2010. Molecular biologic techniques applied to the microbial prospecting of oil and gas in the Ban 876 gas and oil field in China. Applied Microbiology and Biotechnology 86(4):1183-1194. [First two pages]