Impact of Oil-Based Drilling Fluids Emulsification on Tolerance and Hydrocarbon-Degrading Potential of Ralstonia pickettii and Alcaligenes piechandii

Abstract

Biodegradability of drilling fluid waste is essential in the development of environmentally compatible oil and gas drilling. Biodegradation is determined not only by the enzymatic potential, but also microbial tolerance to hydrocarbons. The present study investigated the hydrocarbon degradation and tolerance of Ralstonia pickettii BP20 and Alcaligenes piechandii KN1 to drilling fluids with diesel and low-aromatic continuous phases in respect to their state: non-emulsified oil, direct (O/W) and invert (W/O) emulsions; and the concentrations affecting microbial activity and viability. In general, A. piechaudii KN1demonstrated higher tolerance than R. picketti BP20 did; but, the impacts of different drilling fluids on viability and activity of both microbial strains had similar trends. Microbial growth and hydrocarbons degradation rates increased when diesel was replaced with low aromatic oil, and emulsified. The higher productivity was observed in direct (O/W) emulsions than in invert (W/O) emulsions. Similarly, viability of microorganisms in low aromatic fluids and emulsions was higher than in corresponding diesel drilling fluids. Tolerance to low aromatic fluids increased in the order: non-emulsifier oil < invert emulsion < direct emulsion. In contrast, for diesel based drilling fluids, direct emulsion enhanced, but invert emulsion reduced microbial viability compared to non-emulsified oil.