COLLABORATIVE RESEARCH: Active subsurface methanogenesis and anaerobic organic matter decomposition in a Devonian black shale

合作研究：泥盆纪黑色页岩中活跃的地下产甲烷作用和厌氧有机物分解

• 批准号: 0433801
• 负责人: Anna Martini
• 金额: --
• 依托单位: Amherst College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0433801&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Active; subsurface; methanogenesis

ABSTRACTMicroorganisms employ many novel strategies to derive energy and obtain nutrients, and in doing so alter the chemistry of their environments in ways that are significant for formation and transformation of geologic materials. We propose to investigate one such strategy: microbial methane generation in sedimentary basins. Stable isotopic signatures of CH4, CO2 and H2O in shale formation waters indicate a microbial origin for several natural gas reserves. However, these signatures leave intriguing issues unaddressed. Anaerobic hydrocarbon degradation proceeds by many metabolic pathways including sulfate, nitrate, and iron reduction, fermentation, and methanogenesis, and has been recognized in petroleum reservoirs, polluted aquifers and deep marine sediments. This research will expand understanding of methane generation by exploring anaerobic decomposition of organic matter in subsurface sedimentary rocks leading to economic methane accumulations.The Antrim shale (Late Devonian, Michigan USA) is one of the largest shale gas reserves in North America. Isotopic studies have established that this gas is dominantly microbial in origin. This project will focus on a N-S transect of wells through the main gas-producing trend, sampling formation waters, archived cuttings, and freshly drilled well cores. Prior research on Antrim formation waters by Martini and co-workers provides a solid framework for understanding the subsurface physical and chemical environments within the region. A positive working relationship with energy companies and land owners in northern Michigan allows us an unusual degree of access to the field site, including opportunities to collect fresh material during drilling and to use poorly-producing wells as natural laboratories.Intellectual Merit. This research integrates analytical approaches from aqueous geochemistry, organic geochemistry, thermodynamics, molecular biology and microbiology. We will synthesize our results into a conceptual model that addresses key research questions including: How do analyses of temperature, salinity, nutrients and metabolic substrates reveal thermodynamic and environmental constraints on the activity of these organisms?What does chemical characterization of bitumens, kerogen, and dissolved organic matter reveal about specific sources of organic matter that fuel methane generation in this subsurface environment?What are the 16S and functional gene molecular phylogenies of active microorganisms within Antrim Shale formation waters, and what metabolic roles do these organisms play?Preliminary efforts have determined a high diversity of methanogenic Archaea in formation waters from two Antrim wells, including an entirely new cluster of mcrA genotypes and novel 16S sequences within the Methanomicrobiales, Methanosarcinales, and Methanobacteriales. 16S rRNA-based Bacterial diversity is more limited, confined to sequences closely related to acetate-producing Acetobacterium and within the Syntrophomoadaceae and Syntrophobacteraceae. Surprisingly, no DNA evidence for sulfate- or metal-reducing bacteria has yet been detected. Thus rather than a suite of electron acceptors (O2, NO3, Fe, Mn and SO4) followed by fermentation and methanogenesis (such as found in modern sediments), the subsurface methanogenic environment of the Antrim may more closely resemble documented syntrophic communities in which hydrocarbons are decomposed to acetate and H2, a reaction that is energetically favored only when acetate and H2 are in turn rapidly consumed by methanogens. Our research will explore both of these hypotheses.The broader impacts of this research are varied and far reaching. This study will define an unusual microbial community relevant to human activities. It will also detail how microbial activity in rocks may confound and overprint ancient molecular biosignatures. In addition, the study will shed light on a poorly-constrained source of reduced gases to Earth's atmosphere, important for understanding controls on atmospheric composition, carbon cycling and carbon transformations in earth surface reservoirs. Our collaborative research will increase opportunities in education and training, including a new Five Colleges Biogeochemistry course. We are also initiating partnership with Gaylord High School, the regional public high school serving residents of our field area. Because the gas industry is a large part of the local economy, it will be valuable for students in this modest-income region to gain hands-on experience with scientific endeavors occurring in their backyard. Lastly, by disseminating our results widely, we will improve understanding of gas reserve origins, indices for exploration, and controls on reserve production.

微生物利用许多新的策略来获取能量和获取营养，并在这样做的过程中改变其环境的化学成分，对地质物质的形成和转化具有重要意义。我们建议研究一种这样的策略：沉积盆地中的微生物甲烷生成。页岩地层水中CH4、CO2和H2O的稳定同位素特征表明，几个天然气储量来自微生物。然而，这些签名留下了一些有趣的问题没有得到解决。厌氧烃的降解通过许多代谢途径进行，包括硫酸盐、硝酸盐和铁的还原、发酵和产甲烷，并已在石油油藏、受污染的含水层和深海海洋沉积物中被发现。这项研究将通过探索地下沉积岩中有机质的厌氧分解来扩大对甲烷生成的理解，从而实现经济的甲烷聚集。安特里姆页岩(美国密歇根州泥盆纪晚期)是北美最大的页岩气储量之一。同位素研究证实，这种气体的成因主要是微生物。该项目将通过主要产气趋势、地层水采样、存档岩屑和新钻井芯，以N-S井段为重点。马蒂尼及其同事先前对安特里姆地层水的研究为了解该区域内的地下物理和化学环境提供了坚实的框架。与密歇根州北部的能源公司和土地所有者建立了积极的工作关系，使我们有机会进入油田现场，包括有机会在钻探过程中收集新材料，并将产量较低的油井用作天然实验室。这项研究综合了水化学、有机地球化学、热力学、分子生物学和微生物学的分析方法。我们将把我们的结果综合到一个概念模型中，以解决关键的研究问题，包括：温度、盐度、营养物质和代谢底物的分析如何揭示这些生物活动的热力学和环境限制？沥青、干酪根和溶解有机物的化学特征揭示了在这种地下环境中产生甲烷的特定有机物来源？安特里姆页岩地层水域中活跃微生物的16S和功能基因分子系统发育是什么？这些微生物在代谢中扮演什么角色？初步工作已经确定，在安特里姆两口井的地层水中存在高度多样性的产甲烷古细菌，包括一种全新的MCRA基因簇和新的16S序列和甲烷杆菌。基于16S rRNA的细菌多样性更有限，仅限于与产醋酸酯的醋酸菌密切相关的序列，以及合体单胞菌科和合体单胞菌科。令人惊讶的是，还没有检测到硫酸盐或金属还原细菌的DNA证据。因此，Antrim的地下产甲烷环境可能更类似于有文献记载的合成营养群落，在那里碳氢化合物被分解成乙酸酯和H2，只有当乙酸盐和H2被产甲烷菌迅速消耗时，这种反应才在能量上有利，而不是一系列电子受体(O2、NO3、Fe、Mn和SO4)随后发酵和产甲烷(如在现代沉积物中发现)。我们的研究将探索这两个假设。这项研究的更广泛的影响是多种多样的和深远的。这项研究将定义一种与人类活动相关的不同寻常的微生物群落。它还将详细说明岩石中的微生物活动如何混淆和覆盖古代分子生物签名。此外，这项研究将揭示向地球大气排放的还原气体来源受到的限制很少，这对于理解对大气组成、碳循环和地球表面储气库中的碳转化的控制非常重要。我们的合作研究将增加教育和培训的机会，包括新的五所学院的生物地球化学课程。我们还启动了与盖洛德高中的合作伙伴关系，盖洛德高中是一所为我们田野地区的居民提供服务的地区公立高中。由于天然气行业是当地经济的重要组成部分，对于这个中等收入地区的学生来说，获得在他们后院进行的科学研究的实践经验将是很有价值的。最后，通过广泛传播我们的成果，我们将提高对天然气储量来源、勘探指标和储量生产控制的理解。