高压条件下厌氧产气微生物在多孔介质中的代谢与迁移

Matter transfers are profoundly impacted by the in situ microbial metabolism. With the development of geomicrobiology in deeper strata, the strictly anaerobic metabolism that produces methane is becoming more attractive. Our previous research indicated that, the pressure significantly influence the microbial spread in porous media, except for the phase states of biogenic gases and other fluids. However, the flow in porous media companied with in situ gas production was seldom studied under high pressure like deep subsurface environments. Therefore, the effects of the in situ anaerobic gas-producing process on the mass transportation in porous medium under high pressure became an essential scientific problem. With regard to the complex system, the methods of microbiology, molecular microbiology and flow in porous medium will be integrated in this project, and the high pressure will be simulated by our various high-pressure facilities. The microbial metabolism, adsorption, dispersion and percolation will be investigated in micro and macro scales by one dimensional and two dimensional simulations physically and numerically, to reveal the rules and major mechanisms of the in situ gas-producing activities on flow in porous media. The achievements will contribute the dynamic mechanisms between fields of microorganism and seepage to the further research and applications on microbiology in deep subsurface.

微生物在多孔介质中的原位代谢活动对物质迁移有显著的影响。随着地质微生物的研究与应用向更深地层延展，以甲烷气为最终产物的严格厌氧代谢已成为更受关注的代谢类型。前期研究表明，压力除了影响生物气及流体相态，同样是影响微生物在多孔介质中扩散的重要因素。但目前以原位产气代谢为主的多孔介质渗流实验研究尚未在深地高压条件下系统开展。本研究，拟面向高压下微生物原位厌氧产气与多孔介质中物质迁移过程之间的相互作用这一亟待解决的复杂问题，基于全面、系统的高压模拟装备，综合微生物、分子生物学、渗流力学等多学科研究手段，针对产气微生物代谢、吸附、扩散及渗流过程，建立覆盖从微观到宏观、一维到二维的物理与数值模拟研究体系，揭示深部地层中微生物产气活动对渗流场及物质迁移的作用规律与主导机理。研究成果将有助于建立地下生物场与渗流场之间的动态机制，为深地环境微生物理论深化及应用拓宽提供科学依据。

本项目以开发后期油藏为模式环境，模拟高压、厌氧条件， 以产气微生物、生物气及其产气过程为核心，利用厌氧微生物学、分子生物学、渗流力学等多学科研究手段，从细胞和孔隙微观尺度实现了一维、二维渗流模拟，研究了产气微生物（细胞）及其主要代谢产物（生物气、表活剂）在多孔介质中的吸附、扩散与渗流特征，综合实际油藏尺度的生物-渗流耦合研究成果，揭示了高压条件下多孔介质中产气微生物的迁移规律。. 在模拟地层环境下，厌氧微生物的产气代谢过程要显著高于普通的液相培养条件。而微生物产气对渗流影响显著，机理复杂。结果表明：当产气量较低时，高压环境使得气体溶于石油烃，降低油相粘度提高油相流动性，同时，避免了游离态气体（气泡）在静态条件下对物质输运的阻碍作用。而产气量较高时，出现游离气相，若流体静止，则游离气阻碍液相物质传递，而在流体运动条件下（渗流），游离气可造成孔隙中液相的绕流和流速波动，进而提高剪切应力。. 因此，从微生物提高采收率技术的视角来看，微生物厌氧产气过程发挥着多方面的生物和流体力学作用：生物自发扩散扩大微观波及效率；溶解气提高剩余油输运和剥离效率，即提高洗油效率；游离气形成两相阻力提高液相波及，并依托速度震荡提高洗油效率。也就是说，生物和代谢产物同时发挥两重驱替作用，在油气田开发领域中应用潜力巨大。