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

摘要： 针对大庆油田原油酸值低、应用三元复合驱难度大等特点,筛选了两株具有良好的产酸、产表面活性剂和改善原油物性的菌种,经鉴定分别为短短芽孢杆菌和蜡状芽孢杆菌。这两株菌可以降解原油中重质成分,尤其是高碳链(C₂₀以上)饱和烃,产生大量的胞外有机酸,可使原油酸值平均升高10倍以上。在发酵液中代谢产生混合酯类生物表面活性剂和低分子量有机酸、醇。微生物作用原油后,产生的有机酸在碱性条件下能与合成表面活性剂产生很好的协同作用,使微生物作用后原油与现有三元复合体系形成更低的界面张力,平均比未作用原油体系界面张力降低一个数量级,达到10^-4mN/m数量级。室内天然岩心驱油实验评价结果表明,微生物-三元复合驱结合可比单独三元复合驱驱油效率增加近10% OOIP。

关键词: 微生物, 原油酸值, 界面张力, 三元复合驱, 提高采收率