关键词: 微生物, 原油酸值, 界面张力, 三元复合驱, 提高采收率

Abstract: Aiming at low acid value of crude oil and difficulty of applying ASP flooding in Daqing Oilfield, two stems with better acid productivity, surfactant productivity and oil property improvement capability are screened out, including brevibacillus brevis and bacillus cereus after identification. Both of them can degrade heavy compositions, especially high carbon chain of saturated hydrocarbons(>C₂₀) in crude oil, and produce a large amount of extracellular organic acids to increase acid value of crude oil by more than 10 times. Metabolism occurs in fermentation liquor and produces mixed-esters bio-surfactants, organic acids and alcohols with low molecular-weight. After microorganism acts on crude oil, generated organic acid can synergize with synthesized surfactant in alkali condition so as to form lower interfacial tension (IFT) between oil and current ASP flooding system, averagely decrease one magnitude order of IFT compared to unacted oil system, up to 10^-4mN/m magnitude order. Lab evaluation on natural cores indicates that combination of microorganism and ASP flooding can increase displacement efficiency by about 10% more than individually using ASP flooding.

Key words: microorganism, acid value of crude oil, interfacial tension, ASP flooding, EOR