微电场系统强化残余油生物气化的应用基础研究

Microbial residual oil gasification (MROG) technology has gained growing attention for the development of low permeability reservoir, heavy oil reservoir, and water flooding reservoir. However, the methane production rate and converting efficiency of anaerobic hydrocarbon biodegradation process severely restricts the development of MROG technology. The program intends to develop related research work with microbial electrolysis cell (MES), aiming at solving bottleneck problems in microbial residual oil gasification technology. The introduction of MES system to rate-limited anaerobic hydrocarbon biodegradation process greatly improves the efficiency of extracellular electron transfer and makes up for the reaction energy supply, which in turn activates anaerobic hydrocarbon biodegradation and elevates methane production rate. Meanwhile, CO2 has been directly reduced to CH4 by MES system for electron imputing mechanism and hence a much higher carbon converting efficiency from hydrocarbon to methane is achieved. Reaction kinetics is also put into systematic research and employed to further reveal the influence of microbial community of bio-anode/cathode, substrate composition, temperature, pressure, pH, electrode material, electric potential and current intensity on anaerobic hydrocarbon biodegradation and methane production rate. The model of MES enhanced microbial residual oil gasification system is proposed and can provide the theoretical and engineering basis for promotion and application of the MROG technology.

残余油生物气化技术对以低渗油气藏、稠油油藏、水驱废弃油藏为代表的低品位油气资源的高效开发具有重要意义，然而，烃厌氧降解产甲烷过程的反应速率和转化效率严重制约着该技术的发展，本项目拟利用微生物电解池系统开展相关研究工作，针对性解决残余油生物气化技术中的瓶颈问题。微电场的引入实现了烃厌氧降解限速反应中的高效胞外电子传递和外源能量补给问题，大幅度提升烃厌氧降解产甲烷速率；同时，通过微电场提供的电子输入能够解决CO2还原产甲烷过程中供氢机制，实现不依赖有机物的CO2还原产甲烷作用，大幅度提高了烃厌氧降解产甲烷的转化效率。反应动力学研究有助于揭示生物阳极/阴极，微生物群落及底物组成、温度、压力、pH值、电极材料、电势和电流强度等因素对烃厌氧降解产甲烷速率的影响。微电场系统强化残余油生物气化工程模型的建立为相关技术的推广和应用奠定理论和工程基础。

残余油原位气化是一项针对废弃油藏的前瞻性技术，现阶段其主要问题是产气速率慢，无法满足大规模油田开发的要求。本文通过引入微生物电解池为微生物生长代谢提供能量，实现“微生物-电化学”联合催化，打破微生物厌氧烃降解过程的反应热力学局限，从而加快微生物的甲烷合成速率和CO2甲烷转化速率。.本文的主要结论是：.1. 从油藏中富集驯化获得高产气速率的“互营代谢-产甲烷”菌群，高通量测序分析了其菌群群落结构，结果显示Syntrophomonas、Syntrophus和Syntrophothermus等具有互营代谢特点的微生物成为细菌的优势种属；Methanoculleus、Methanobacillus和Methanobacterium 等能够以H2+CO2和甲酸盐为底物合成甲烷的微生物成为古菌的优势种属。.2. 产气分析表明该菌群的甲烷合成速率达到了5.3 L/m3•day，然后在同样条件下，用外加0.15 V的单室微生物电解池强化该菌群的甲烷合成，甲烷合成速率提高了173%，达到了14.7 L/m3•day，法拉第效率由64.7%提高到123.2%。.3. 研究了微生物电解池强化甲烷合成速率的影响因素，底物、矿化度、电极材料和电势均能够影响甲烷的合成速率，其中电势能显著影响甲烷的合成速率。在外加1.5 V电势的条件下，该菌群的甲烷合成速率达到了24 L/m3•day，甲烷合成速率提高了355%。.4. 双室微生物电解池系统研究证明添加电压能够明显提高产甲烷菌的CO2甲烷转化速率。在外加8.45 V电压时，室内实验录得的最大的甲烷合成速率为54.3 L/m3•day，甲烷合成速率比非微生物电解池强化提高了515.4%。.5. 温度、pH、 矿化度、电极材料和电压能够影响CO2的甲烷转化速率。.6. 在油藏环境条件下，油井间添加电压存在一定的困难，可以根据产甲烷菌的需求及安全性问题，注入氮气、CO2和H2的混合气体，提高微生物的甲烷合成速率与转化速率。该方案是是残余油微生物气化技术现场实施可行性重要途径。