Abstract
With the development of molecular ecology, increasing low-abundance microbial populations were detected in oil reservoirs. However, our knowledge about the oil recovery potential of these populations is lacking. In this study, the oil recovery potential of low-abundance Dietzia that accounts for less than 0.5% in microbial communities of a water-flooding oil reservoir was investigated. On the one hand, Dietzia sp. strain ZQ-4 was isolated from the water-flooding reservoir, and the oil recovery potential was evaluated from the perspective of metabolisms and oil-displacing test. On the other hand, the strain has alkane hydroxylase genes alkB and P450 CYP153 and can degrade hydrocarbons and produce surfactants. The core-flooding test indicated that displacing fluid with 2% ZQ-4 fermentation broth increased 18.82% oil displacement efficiency, and in situ fermentation of ZQ-4 increased 1.97% oil displacement efficiency. Furthermore, the responses of Dietzia in the reservoir accompanied by the nutrient stimulation process was investigated and showed that Dietzia in some oil production wells significantly increased in the initial phase of nutrient injection and sharply decreased along with the continuous nutrient injection. Overall, this study indicates that Dietzia sp. strain has application potential for enhancing oil recovery through an ex situ way, yet the ability of oil recovery in situ based on nutrient injection is limited.
Highlights
Oil reservoirs harbor diverse microbial populations that contribute to oil exploitation [1,2,3]
Hydrocarbon-degrading bacteria are one of the most widely studied populations because of their important roles in the microbial enhanced oil recovery (MEOR) process. ese microorganisms are generally able to produce surfactants with crude oil as a sole carbon source [4,5,6]. e produced surfactants can lower oil viscosity and oil-water interfacial tension to improve the recovery of residual oil underground
A Dietzia sp. strain ZQ-4 was isolated from the water-flooding reservoir, and the oil recovery potential was evaluated from the perspective of metabolisms and oil-displacing test
Summary
Oil reservoirs harbor diverse microbial populations that contribute to oil exploitation [1,2,3]. Hydrocarbon-degrading bacteria are one of the most widely studied populations because of their important roles in the microbial enhanced oil recovery (MEOR) process. Many researchers devoted to isolate hydrocarbon-degrading bacteria from oil reservoirs and to investigate how these microorganisms improve oil recovery [5, 8,9,10,11,12,13,14]. Ese microbial populations were demonstrated to be able to enhance oil recovery in laboratory, and some species were found showing positive responses with incremental oil in laboratory and MEOR field trials [5, 8, 9, 22, 23]. The responses of Dietzia in the reservoir accompanied by a nutrient stimulation process were investigated. e results will benefit our understanding about the roles of low-abundance Dietzia in the MEOR process
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