油藏注采系统中微生物群落的时空分布、变化规律及其影响因素

Water-flooding is an oil recovery process widely employed worldwide. After long-term water-flooding, oil reservoirs harbor highly diverse microbial communities associated to oil recovery, leading the intensive development of Indigenous Microbial Enhanced Oil Recovery technique (IMEOR). Although it has been proved validity in field trial, this technology also has some limitations, such as lacking of systematic theories and unstable during enhancing oil recovery. Despite the significant influence of microbial community diversification on oil displacement efficiency, microbial distribution and succession in petroleum reservoirs, particularly, in the injection and production systems, still remains poorly understood. In this direction, using high-throughput sequencing technique and statistical analysis, we comprehensively investigated the community composition and succession across space and time and the major drivers in a water-flooding petroleum reservoir in Daqing Oil Field. The objectives are to elucidate microbial community distribution across space and time in water-flooding petroleum reservoir; to expound the core microbial community in the microbial populations of water-flooding reservoir. In combination with culture and core-flooding test in laboratory, the major factors, in particular, the environmental factors or stochastic effect, in shaping microbial structure across a broad range of space and time scale will also be determined. All of these researches above could enrich our knowledge about microbial community distribution and succession along with injected water flowing in petroleum reservoir, and provide scientific guidance to efficiently stimulate reservoir microorganisms to improve oil recovery.

解析油藏微生物群落组成是开展内源微生物驱油的先决条件。目前，激活油藏內源采油功能菌以提高石油采收率技术已在现场成功应用，并取得较大进展。但是，由于油藏注采系统是一个开放的体系，微生物群落组成的波动性较大，造成同一油藏在不同时期的微生物激活效果和驱油效率存在不稳定性，这严重制约了该技术的工业化推广。因此，本课题将油田地表注水系统和油藏注采井作为一个研究整体，在时间和空间尺度上，利用高通量测序技术和统计学分析方法考察整个油田注水开发系统及其周围地表环境中微生物群落的分布与演替，揭示核心微生物类群的组成与漂移，剖析影响群落变化的主控因素；在此基础上，结合室内培养与岩芯物理模拟技术阐明地面及地下的环境因素及菌群演变的随机性效应对油藏微生物群落组成与分化的影响。本课题对深入认识油藏微生物群落分布及演替的客观规律、调控微生物驱油过程和实现稳定的降水增油效果具有重要的理论意义及应用价值。

本课题为国家自然科学基金青年基金项目“油藏注采系统中微生物群落的时空分布、变化规律及其影响因素（31500414）”。课题执行期间发表SCI二区期刊论文4篇。主要完成两方面研究工作：.1）油藏微生物分布及其与油藏环境因素之间相关性。本课题采用16S rRNA测序技术对我国22个油藏区块中微生物群落的组成和分布进行了比较分析。菌群组成分析表明，不同油藏环境微生物群落之间存在较大差异，但存在共有微生物类群。多元回归树MRT、典范对应分析CCA和RDA分析表明，地理隔离、温度、地层水矿化度和pH是驱动油藏微生物群落分化的主要动力。.2）油田注采系统中微生物群落分布及注入水中微生物能否进入地层从而影响油藏储层中微生物群落。采用16S rRNA高通量测序技术对油藏注采系统（注水站、注水管线、注水井、采油井和采出液回收处理站）中微生物群落组成与分布进行了系统研究。结果表明，与周边土壤环境相比，油藏注采系统微生物群落具有明显不同（P<0.001），且油藏注采系统中微生物群落表现出显著的生境专一性。注水站和注水井井口位置微生物群落具有较高相似性（r=0.79，P<0.05），Betaproteobacteria和Alphaproteobacteria为优势微生物类群；注水井井口和井底微生物群落表现出显著差异性，Deltaproteobacteria、Clostridia、Anaerolineae和Synergistia在井底为优势微生物类群；采油井中Gammaproteobacteria和Betaproteobacteria和Epsilonproteobacteria为优势微生物类群。油藏地面注水系统和注水井近井地带的古菌微生物群落组成差异性不显著，随注入水流经地层，古菌群落发生显著变化。在水井井口、水井井底和采油井中，细菌群落与环境因子总磷、NO3-和SO42-表现出显著相关性，古菌落与总氮表现出显著相关性。.共现性分析表明，大量微生物类群同时出现在注水井井口、注水井井底和采油井中，且注水井井底和采油井中共有微生物类群占采油井微生物类群的比率与油井渗透率存在较强相关性(Pearson, r=0.324, P=0.081)，其中两个区块表现出显著相关性0.961和0.911。基于荧光蛋白标记菌株运移的岩芯模拟实验表明，微生物可以随注入水进入油藏储层环境。