Analysis Of Microbial Metabolites In The Production Water From Oil Well

Reservoir is a complex environment, where the microbial species are various and their metabolites of petroleum hydrocarbons are different. Some of the metabolites can improve fluid chemical and physical properties, which is helpful for the flow and mining of crude oil. However, the knowledge about the microbial metabolites is still limited. This article focused on the microbial metabolites in the production water from oil wells, including gas, organic acids, the hydrocarbon dissolved in water and surface tension, which may provide evidence for further understanding the microbial activities in the reservoir and exploring the effects of metabolites.The head space gases of production water samples from six oil wells were quantitatively determined by gas chromatography. The organic acids in production water were qualitatively and quantitatively analysed, through butanol esterification and GC-MS. The dissolved hydrocarbon in production water and surface tension were also determined. In addition, the microorganisms in production water were enriched using glucose and crude oil as carbon source, the metabolites were analysed by GC and GC-MS and the surface tension of fermented broth were determined by surface tensiometer.1) The results from gas chromatography shown that all head space gases of production water contain the methane and carbon dioxide, the content of carbon dioxide varied from0.3to64.7mmol/L, that of methane from0.2to16.5mmol/L. The content of carbon dioxide is higher than methane. Some samples had a few ethane and isobutane. The main composition of volatile organic acids in production water is acetate, which content is from1.3to368.8mg/L, and there were a little formic acid, propionic acid, butyric acid and iso-butyric acid. A variety of nonvolatile organic acids such as diacids, aromatic acid and long chain fatty acids were also detected. The butyric acid may come from branched alkane oxidation, diacids revealed that there is the oxidation at double ends of liner hydrocarbon and the oxidation of cyclic hydrocarbon, aromatic acid implied the aromatic hydrocarbon oxidation. The long chain acids may be produced through the long alkane oxidation.2) Canonical correspondence analysis (CCA) shown that the volatile organic acids in the production water from oil well have no significant relativity with reservoir conditions such as temperature, crude oil viscosity, permeability but significant relativity with inorganic ions in production water. The volatile organic acids correlated with the bacteria and the archaea in the reservoir. 3) For further understanding the metabolism and metabolites of microorganisms in oil reservoir, the enrichment method using the glucose and crude oil as carbon source was adopted. The carbon dioxide was main component in gas without methane when glucose was used and the volatile organic acid was the acetic acid, which content is from1.6to337.5mg/L, without propionic acid and butyric acid. However, formic acid can be detected in some samples. The carbon dioxide was also main component in gas without methane, the main component of volatile organic acids is formic acid, which content was from27.8to340.2mg/L with other three acids, acetic, propionic and butyric acids, though butyric acid could not be detected in some samples. Those results deepened the cognition of carbon source usage and metabolites of microbes in oil reservoir.