循环激活本源微生物提高原油采收率的基础研究

Oil reservoirs in deep subsurface are environments with high temperature and high pressure. It is well known that pressure is a key factor for the growth of microbes, however, few studies are conducted to reveal the influence of pressure on the growth and metabolism of indigenous microbes in oil reservoir. In this study, a cyclic stimulation of indigenous MEOR strategy is proposed based on the concern of high pressure. Firstly, we are focusing on the microbial diversity and MEOR functions of microbes in oil reservoirs under high pressure. Samples are special backflow fluids from injection wells and airtight cores samples collected during drilling new oil wells. MEOR functional indigenous microbes are stimulated and isolated under conditions of oil reservoirs, and MEOR functions are identified through metagenomic sequencing and isotope labelling. Based on the results obtained in the first period of the project, a cyclic stimulation indigenous MEOR strategy is carried out as follows: Nitrate-reducing bacteria (NRB) are stimulated in the surface wastewater from three-phase separations to inhibit the growth of sulfate-reducing bacteria (SRB). Which is followed by the air flotation technology with small bubbles that can stimulate hydrocarbon degrading bacteria. Finally targeted stimulated microbes are anaerobic microbes in deep subsurfaces. The three stages of stimulation indigenous microbes form a biofield consisted of aerobic and anaerobic indigenous microbes, combine surface wastewater treatments with subsurface indigenous MEOR to enhance oil recovery.

深部油藏为高温高压环境，压力是微生物生长代谢的重要环境影响因子，但目前关于压力对油藏微生物生长代谢的研究报道较少。本项目提出循环激活本源微生物驱油新方法。首先通过注水井返排液或打新井时密闭取芯法取得深部油藏本源微生物样品，然后模拟油藏原位温度、压力和盐度等条件，定向富集采油功能菌，筛选和优化其激活体系，采用稳定同位素标记的高通量宏基因组学技术，研究油藏本源微生物的多样性和共代谢功能，同时分离耐高压采油功能菌；在此基础上，构建循环激活本源微生物驱油新方法，首先在过滤前污水中激活硝酸盐还原菌(NRB)抑制硫酸盐还原菌(SRB)，控制硫化氢产生；然后采用微小气泡气浮技术，激活过滤后污水中的烃降解菌群；最后激活油藏中厌氧采油功能菌群。三阶段激活本源微生物，构建好氧厌氧采油功能菌生物场，将地面污水生化处理与地下油藏本源菌驱油有机结合起来，达到高效提高原油采收率目的。

深部油藏为高温高压环境，压力是微生物生长代谢的重要环境影响因子，但目前关于压力对油藏微生物生长代谢的研究报道较少。本项目提出循环激活本源微生物驱油新思路。首先在过滤前污水中激活硝酸盐还原菌(NRB)抑制硫酸盐还原菌(SRB)，控制硫化氢产生；然后采用定向激活过滤后采油污水中的烃降解和产生物表面活性剂等采油功能菌群；最后通过地面采油菌代谢物激活油藏中的厌氧采油功能菌群。三阶段激活本源微生物，构建好氧厌氧采油功能菌生物场，将地面污水生化处理与地下油藏本源菌驱油有机结合起来，达到高效提高原油采收率目的。研究结果表明，原位油藏中存在耐恶劣环境条件的采油功能菌，尤其是能产内生孢子的芽孢杆菌类、肠杆菌、梭菌、西瓦氏菌、假单胞菌类等，在原位油藏中，厌氧下具有高代谢活性，降解石油烃或者其它有机营养物，产生驱油代谢物，剥离岩石表面原油，通过原位生物自乳化改善原油流动性，提高原油采收率；本项目从油藏环境首次分离到耐压的铁还原菌如西瓦氏菌、梭菌和芽孢杆菌等，在原位油藏下具有高铁还原活性，协同作用降解石油烃；结合两个油田的矿场试验，在采油污水中定向激活有益菌硝酸盐还原菌（NRB），能使有害菌硫酸盐还原菌（SRB）降低到100个/ml以下，硫化氢浓度降至零，已经产生的黑色生物硫化物沉淀完全消失；结合海上油田现场试验，构建稳定的高效耐高盐度厌氧和好氧功能菌群，将采油污水COD降低至60以下，氨氮降低至5以下，并详细研究了污水生化处理系统复杂微生物菌群的协同作用和构效关系等机制，能实现油田地面污水处理达到国家一级排放标准，首次在海上油田工业化应用。表明循环激活原位油藏的本源微生物，能完美实现地面污水生化处理和地下原位油藏提高原油采收率，绿色环保。创新点：（1）提出地面激活好氧菌和地下激活厌氧菌的循环激活本源微生物驱油新方法；（2）首次从油藏中分离到耐压铁还原菌；（3）原位油藏下原油的生物自乳化。