Aerobic degradation of oil-based mud drilling fluid by in situ bacteria in the Hawizeh Marshes

The increasing global demand for hydrocarbon has brought new challenges in the petroleum reservoir's drilling process. Non-biodegradable chemical additives are used in drilling fluid and it leads to endangering the environment and personnel safety. Thus, there is a great need for new biodegradable drilling fluid additives that can protect the environment and personal safety while drilling is done well. This study with help of microbial analysis investigates the effects of in situ bacteria to degenerate the gasoline inside the oil-based mud, in the returned lubricant from one of the oil wells next to the Hawizeh Marshes. Four types of bacteria inside the oil-based mud were observed. According to the high growth and degradation of crude oil, one strain was selected. Determination of the coagulase and clumping test shows that the isolated strain belongs to staphylococcus. We investigate the performance of the staphylococcus bacterium on the lubricant from biological degradation aspects, using a gas chromatography technique. It was observed that the exposure of a small amount of the bacteria against 10 mL of lubricant indicates a considerable degree of degeneration, only in a few days. The residual crude oil in the culture medium was analyzed by gas chromatography (GC) and SARA. The results confirmed that the strain can degrade crude oil and produce lighter hydrocarbon. The saturate fraction increased about 23%, while the Resin and Asphaltene fractions decreased about 11% and 12%, respectively. This research is the first report on the characterization of crude oil-degrading bacteria from in situ bacteria at Hawizeh Marsh and by using this bacterium in the field the effect of oil pollution can be reduced on this marsh environment in a few days.