Reducing Oil Content Of Oil Based Mud By Indigenous Microbial Consortium

Oil is an important energy.With the growth of social economy,the demand for oil is rising,and people show more attention on the problem cased by oil.Oil-base mud is created in the process of oilfield production,which contains higher petroleum material and is difficult to deal with.This study used the indigenous microbial consortium to deal with oil-base mud.Compared with physical and chemical methods,the microbial method was more economic and will not cause secondary pollution.In this paper,oil-based mud was used as the research object.The effect was not ideal by using microbiological method to degradate oil-base mud directly.So we used the surfactant cleaning method to preprocess oil-base mud,adding with shake flask test and microcosm experiments to explore the degradation effect of oil-base mud by indigenous microbial consortium.The main conclusions were as follows:(1)Total petroleum hydrocarbon(TPH)content in oil-based mud was 135.36±7.78 g/kg which showed the pollution was serious;pH value was 9.05±0.05 which showed the oil-based mud was alkaline;Salinity value was 1.20±0.02%;Moisture content was 2.17±0.64%;The content of organic matter,available N and available P were 20.36±0.05%,44.34±13.53 mg/kg and 23.79±0.05 mg/kg,respectively.(2)Four indigenous bacterias was isolated from oil-based mud:Y1,Y2,Y3 and Y4.Four strains belong to Bacills sp by 16S rRNA gene sequence identification and phylogenetic tree analysis.Y1 was similar to Bacillus cereus and the similarity was 99%.Y2 was similar to Bacillus pumilus and the similarity was 99%;Y3 was similar to Bacillus subtilis and the similarity was 99%;Y4 was similar to Bacillus cereus and the similarity was 99%.(3)Oil-based mud had high oil content which leaded to the results that microorganism method had no effect on the degradation the oil-based mud.After surfactant cleaning of oil-base mud preprocessing,oil content of oil-based mud declined from 13.536%to 6.735%within 1 hour.(4)To study the optimal degrading condition of four strains,a single factor experiment was carried out on surfactant cleaned oil-based mud.The results showed that The results showed that the optimum range of pH,salinity and temperature was 7?9,0.3%?1.3%and 30??37?,respectively.Under the optimal conditions,the degradation rate of Y1 was 38.82%;the degradation rate of Y2 was 28.26%;the degradation rate of Y3 was 31.5%;the degradation rate of Y4 was 39.4%.(5)Based on the optimal condition of results,shake flask experiment was carried on the oil-base mud and the degradation rate of TPH was 42.61%.The microcosm experiment was used on further degradation of the oil-based mud.After 35 days,the degradation rates of TPH in oil-base mud by Y1,Y2,Y3,Y4 and mixed bacteria group were 48.32%,44.48%,45.76%,50.94%and 67.68%,and the degradation effect of the mixed strains was obviously higher than that of single strain.We used the surfactant cleaning method to preprocess oil-based mud,adding with shake flask test and microcosm experiments to reduce oil content of oil-based mud.The oil content of oil-based mud was reduced from 13.536%to 1.135%.This method will provide basis for oil-based mud treatment technology.