Thermophilic Bacteria in UAE Environment Can Enhance Biodegradation and Mitigate Wellbore Problems

Abstract

Abstract Several strains of thermophilic bacteria were isolated from the environment of the United Arab Emirates. These bacteria show extra ordinary resistance to heat and have their maximum growth rate ranging from 45C to 80C. This paper investigates the potential of using these facultative bacteria for both in situ and ex situ bioremediation of oil spills and microbial enhanced oil recovery. In a series of batch experiments, bacterial growth was observed using a Computer Image Analyzer following a recently developed technique. Experiments show clearly that the growth rate is high in the presence of crude oil. This is coupled with a rapid degradation of the crude oil. These bacteria were found to be ideal for breaking down long-chain organic molecules at a temperature of 80C, which is the typical temperature of the light oil reservoirs in the Gulf region. These bacteria were also prolific at 45C, which is the typical ambient temperature of the region in the summer months. The same strains of bacteria are also capable of surviving in the presence of saline environment that can prevail in both sea water and reservoir connate water. This observation prompted further investigation into the applicability of the bacteria in microbial enhanced oil recovery. These bacteria were found to decompose crude oil as well as asphaltenes. Most of UAE crude oils are asphaltic and pose serious production problems of near-wellbore plugging. Thermophilic bacteria can effectively clean damaged wells and the vicinity of wellbores. Similarly, the bacteria appeared to breakdown the microstructure of waxy materials. Even though, this did not yield to high degradation rate, the permeability damage due to wax deposition could be mitigated. Finally, mathematical models were developed for determining the degradation rate in the presence of thermophilic bacteria. Corrections are made to accommodate both the effect of growth and propagation in the porous medium in the vicinity of the wellbore. Excellent match was found between experimental and numerical observations. Predictive runs were conducted to observe the role of various governing parameters prevalent in both environmental and enhanced oil recovery schemes.