| The distribution of sulfureted hydrogen (H2S) as well as sulfate-reducing bacteria (SRB) distribution and diversity in crude oil and oilfield production water samples from a oil gathering and transferring system in Changqing Oilfield of China were investigated by methylene blue colorimetric method, the most probable number technique and sequence analysis of the 16S rRNA gene, respectively. At the oil gathering and transferring system which from oil well through oil flowstation and then to oil comprehensive treatment station, the results showed that in oil samples, the content of H2S were 105.80, 99.70, and 24.57 mg·L-1, respectively; and the count of SRB were 98, 300, and 680 CFU·100 mL-1, respectively. In water samples, the content of H2S were 1.13, 2.80, and 3.49 mg·L-1, respectively; and the count of SRB were 9500, 40000, and 76000 CFU·100 mL-1, respectively. The abundance of SRB in the water samples is about 100 times than that in the crude-oil samples. High concentration of H2S in oil well inhibited the growth of SRB, thereby the count of SRB in oil well were small. With the reduction of H2S concentration, the actions of inhibition weakened and disappeared, then the number of SRB were gradual increase in the gathering and transferring system. For the initial concentration of H2S in water samples was low, and the number of SRB were large, then the content of H2S increased gradually with the number of SRB were increased. Sequence analysis of the 16S rRNA gene indicated that SRB related to Desulfovibrionaceae sp. and Desulfococcus sp. were detected in the water and crude oil samples, simultaneously. However, SRB related to Desulfomonilesp., Desulfotomaculumsp. and Desulfosarcina sp. were detected in the water samples but not in crude-oil samples. Abundance of SRB was increased due to the variation of environmental condition during the period of oil gathering and transferring process. |
