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1.
综合大洋钻探计划311航次沉积物中自生碳酸盐岩碳、氧稳定同位素特征 总被引：4，自引：3，他引：1
为了探索水合物背景下沉积物中自生矿物响应,对采自综合大洋钻探计划（IODP）311航次沉积物中自生碳酸盐岩颗粒进行了矿物组成、形貌特征和碳、氧稳定同位素特征等研究。X光粉晶衍射（XRD）和扫描电镜（SEM）结果显示碳酸盐岩颗粒的主要矿物成分是铁白云石和方解石,呈多孔状结核和不规则状集合体产出。碳酸盐岩颗粒的碳稳定同位素δ13CPDB低至-41.50‰,证实其碳源源自甲烷,其成因与甲烷厌氧氧化过程有关,印证了研究区存在海底甲烷渗漏现象,是甲烷水合物赋存区重要的识别标志之一。碳酸盐岩颗粒的氧稳定同位素δ18OPDB总体上随着沉积物深度增加而减小,可能指示沉积物的背景温度由下而上（从早到晚）逐渐降低。研究结果提供了现代海洋天然气水合物背景下沉积物中自生碳酸盐岩的碳、氧稳定同位素记录,对于寻找我国海域天然气水合物资源,探索地史时期古海洋沉积物中类似的甲烷事件记录具有重要的理论和实践指导意义。 相似文献
2.
海底天然气水合物分解与甲烷归宿研究进展 总被引：5，自引：1，他引：5
综述了近年来天然气水合物分解与甲烷归宿等方面的研究成果。天然气水合物的汇聚与地质构造或地层圈闭有关，其溶解受物质转换控制，分解则受热转换控制。水合物释放甲烷的运移方式包括分散式、中心式和大规模排放式。缺氧氧化和耗氧氧化是甲烷在海洋环境中的2种主要转化方式。天然气水合物释放甲烷的最终归宿主要为：①重新形成天然气水合物；②形成化能自养生物群落和沉淀出碳酸盐沉积；③与氧发生氧化后转变为CO2；④直接排放进入到大气中。沉积物中的微构造、化能自养生物群落、自生碳酸盐矿物及其碳氧同位素组成是水合物释放事件的指纹记录。 相似文献
3.
天然气水合物分解及其生态环境效应研究进展 总被引：10，自引：2，他引：8
了解大陆／大洋边缘地区天然气水合物形成与分解及其在海底沉积物、水体及海底化学自氧生物群落中的一系列物理、化学及生物作用有助于我们在全球和区域尺度上探讨天然气水合物分解对气候变化的影响;天然气水合物在碳循环中的作用和大陆边缘流体活动与物质交换机制等问题。从水合物分解与全球变暖、贫／缺氧甲烷氧化作用、自生矿物沉淀、化学自养生物群落等方面综述了水合物的环境生态效应研究进展。天然气水合物的形成／分解及
其对海洋乃至全球环境生态变化的影响,深刻地反映了地球上岩石圈、水圈、大气圈和生物圈之间相互联系与相互作用,生物,特别是微生物对全球CH 4的平衡和自生矿物沉淀至关重要。 相似文献
4.
海底天然气渗漏系统微生物作用及冷泉碳酸盐岩的特征 总被引：18，自引：3，他引：18
海底天然气渗漏系统是全球海洋环境中广泛分布的自然现象。部分渗漏天然气通过细菌作用转变为二氧化碳,同时海水硫酸盐被还原为硫化氢, 与孔隙水中的钙和铁结合而沉淀冷泉碳酸盐岩。冷泉碳酸盐岩的常见矿物有微晶方解石、文石、白云石和黄铁矿。冷泉碳酸盐岩常发育一些特殊的组构, 如黄铁矿环带结核、溶蚀面、平底晶洞、凝块和向下生长的叠层石组构等。碳酸盐岩特别负的δ13C值指示碳来源于生物成因的甲烷, 而18O富集可能与天然气水合物的分解有关。冷泉碳酸盐岩中黄铁矿的δ34S值低于海水的, 这指示硫来源于微生物还原的海水硫。冷泉碳酸盐岩中的生物标志化合物及其极负的δ13C值指示微生物的生命代谢活动。 相似文献
5.
伴生碳酸盐矿物在海底与天然气水合物伴生是一种普遍现象,但在陆上冻土区中报道较少。以近两年在祁连山冻土区发现天然气水合物伴生的碳酸盐矿物为研究对象,根据对含碳酸盐样品的显微镜观察及矿物分析,确定了伴生碳酸盐的矿物种属及赋存状态。按碳酸盐矿物组成及地质产状的不同,其赋存状态分成4种类型,即白色薄层状、烟灰色菱形晶簇状、深灰色薄壳状、微细浸染状。根据不同赋存形态碳酸盐的C、O同位素特征,认为烟灰色菱形晶簇状方解石或呈(云烟状)微晶方解石可能与天然气水合物分解有关。碳酸盐C、O同位素随深度变化特征表明在一定深度处可能存在着烃类物质的活动,即天然气水合物分解,导致碳酸盐的矿物生成。 相似文献
6.
天然气水合物成因探讨 总被引：18，自引：0，他引：18
天然气水合物是未来的能源资源。其分布于极地地区、深海地区及深水湖泊中。在海洋里,天然气水合物主要分布于外大陆边缘和洋岛的周围,其分布与近代火山的分布范围具有一致性。同位素组成表明天然气水合物甲烷主要是由自养产甲烷菌还原CO2形成的。典型的大陆边缘沉积物有机碳含量低（＜0．5％～1．0％）,不足以产生天然气水合物带高含量的甲烷。赋存天然气水合物的沉积物时代主要为晚中新世-晚上新世,具有一定的时限性,并且天然气水合物与火山灰或火山砂共存,表明其形成与火山-热液体系有一定联系。火山与天然气水合物空间上的一致性表明,天然气水合物甲烷的底物可能主要是由洋底火山喷发带来的CO2。由前人研究结果推断 HCO－3在脱去两个O原子的同时,可能发生了亲核重排,羟基 H原子迁移到 C原子上,形成了甲酰基（HCO－）,使甲烷的第一个 H原子来源于水。探讨了甲烷及其水合物的形成机制,提出了天然气水合物成因模型。 相似文献
7.
冷泉流体沉积碳酸盐岩的地质地球化学特征 总被引：39，自引：3，他引：36
冷泉流体是指来自海底沉积界面之下的低温流体以喷涌和渗漏方式注入盆地, 并产生系列的物理和化学及生物作用, 这种作用及产物称为冷泉?它是继洋中脊以盆下源中高温流体的热泉被发现和研究之后的又一个新的盆地流体沉积领域?日前研究较多的是以水? 碳氢化合物 (天然气和石油) ? 硫化氢? 细粒沉积物为主要成分, 温度与海水相近的流体, 广泛发育于活动和被动大陆边缘斜坡海底?冷泉流体沉积体系发育高密度的化学自养生物群, 以碳酸盐岩和天然气水合物为主, 有少量的硫化物和硫酸盐等?冷泉碳酸盐岩的产状有丘? 结核? 硬底? 烟囱? 胶结物和小脉等, 以化学自养生物碎屑和多期次的自生碳酸盐胶结物组成的生物丘最为常见, 它在物质来源? 形成环境? 形成作用等方面与传统来源于海水碳的碳酸盐岩建隆不同, 用术语 C h e r m o h e r m 表示, 以区别于传统海水碳酸盐岩建隆术语b i o h e r m s ? l i t h o h e r m s ? p s e u d o b i o h e r m s 和 b i o s t r o m e s ?地层中石化的化学自养生物丘常是含有大量底栖生物化石的碳酸盐岩建隆产于深水相沉积地层中, 在沉积环境和相分析上出现纵向和横向的不连续, 甚至出现反常现象?矿物以镁方解石? 白云石和文石为主, 与传统的碳酸盐岩相似, 在地球化学组成上最大的区别是冷泉流体沉积碳酸盐岩的碳来源于冷泉体系中的细菌生物成因碳, 具有特别负的碳同位素值?冷泉在海底主要沿构造带和高渗透地层呈线性群, 或围绕泥火山或盐底劈顶部呈圆形或不规则状冷泉群分布,或以海底地形低凹处和峡谷转向处呈孤立冷泉形式产出?冷泉流体以沉积建造流体为主?上覆快速堆积? 成岩压实和胶结作用? 构造挤压和变形作用? 深部的后生作用和成岩作用? 海底沉积物中的天然气水合物分解作用是建造流体向上运移进入海底成为冷泉的驱动力?冷泉碳酸盐岩的沉积作用主要有胶结作用? 充填作用和生物化学沉积作用?冷泉流体中的碳主要是以甲烷为主的碳氢化合物形式存在, 经微生物作用转变为 C O2 ,最终形成冷泉碳酸盐岩? 相似文献
8.
华北地台中元古代碳酸盐岩中的微生物成因构造及其生烃潜力 总被引：6，自引：3，他引：3
华北地台中元古界主要由环潮坪石英砂岩、浅海碳酸盐岩和浅海—泻湖相暗色页岩3种沉积相组合构成,以陆表海浅水碳酸盐岩占主导。碳酸盐岩中除含有丰富的微古植物、宏观藻类和微生物建隆外,还发育大量的微生物成因构造(MISS)和微生物诱发的碳酸盐沉淀(MMCP)。微生物席和MISS构造在高于庄组上部(约1.6 Ga)和雾迷山组下部(约1.45 Ga)碳酸盐岩中尤为发育,表明活跃的微生物活动和高有机质产量。在石化微生物席中,发现有丝状、球状细菌化石和草莓状黄铁矿;围岩中发现有针状文石、花瓣状重晶石、放射状菱铁矿、铁白云石和葡萄状碳酸盐胶结物等多种自生碳酸盐矿物,指示甲烷厌氧氧化(AOM)导致的自生碳酸盐沉淀。中元古代的温暖气候和海洋分层、缺氧、硫化条件有利于微生物的高生产量和高有机质埋藏率。气隆构造和核形石状碳酸盐结核反映浅埋藏条件下活跃的成烷作用和甲烷排放,围岩和MMCP中富沥青质。华北地台中元古界富微生物席碳酸盐岩有良好的生烃潜力,有可能形成重要的烃源岩。据微生物席、MISS构造及MMCP的研究,初步估算华北地台中元古代碳酸盐岩的概略生烃潜力约为10×108t石油当量。 相似文献
9.
Chemosynthetic carbonates, identified by isotopic, palaeoecological and sedimentological features, are concentrated in middle-late Miocene satellite and foredeep deposits of the northern Apennines. Chemoherms in the foredeep are hosted in thick pelitic intervals, probably deposited in intrabasinal structural highs, which are entirely or partly involved in large slumps, in many cases associated with extrabasinal slides. Sediment textures in carbonates and in the enclosing foredeep pelitic sediments indicate a link between hydrocarbon-fluid venting, sediment deformation and mobilisation, and tectonics. The intensity and style of fluid release phases directly influenced chemoherm typology, and also determined overpressure conditions in low shear strength pelitic sediments, favouring sediment mobilisation and influencing slope instability, which widely affected the Apennine foredeep. Chemosynthetic carbonates are associated with sites of tectonically fractured and compressed sediments in the Apennine foredeep-thrust belt system, thus indicating a relation with the tectonic loading of the Apennine thrust-sheets, which favoured fluid expulsion along forerunner faults. Possible gas hydrate contributions to fluid expulsion processes are discussed, based on sediment textures compared with modern vent areas. Finally, sediment instability may have facilitated a large amount of fluid escape, thus stopping carbonate precipitation. 相似文献
10.
Microbial Mats in the Mesoproterozoic Carbonates of the North China Platform and Their Potential for Hydrocarbon Generation 总被引：2，自引：0，他引：2
The well-preserved Mesoproterozoic succession in the North China platform consists mainly of three llthological associations including peritidal quartz sandstone, shallow marine and lagoonai dark to black shales, and shallow epeiric carbonates, with a total thickness of up to 8 000 m. In addition to well-documented microplants, macroalgae, and microbial buildups, abundant microbially induced sedimentary structures (MISS) and mat-related sediments have been recognized in these rocks. Intensive microbial mat layers and MISS are especially well preserved in the carbonates of the upper Gaoyuzhuang (高于庄) (ca. 1.5 Ga) and lower Wumishan (雾迷山) (ca. 1.45 Ga) formations, Indicating diversified microbial activities and a high organic production. In these petrified blomats, putative microbial fossils (both coccoidal and filamentous) and framboidal pyrites have been identified. The abundance of authigenic carbonate minerals in the host rocks, such as, acicular aragnnites, rosette barites, radial siderites, ankerites, and botryoidai carbonate cements, suggests authigenlc carbonate precipitation from anaerobic oxidation of methane (AOM) under anoxic/euxinic conditions. Warm climate and anoxic/euxinic conditions in the Mesoproterozoic oceans may have facilitated high microbial productivity and organic burial in sediments. Although authigenic carbonate cements may record carbonate precipitation from anaerobic methane oxidation, gas blister (or dome) structures may indicate gas release from active methanogenesls during shallow burial Bituminous fragments in mat-related carbonates also provide evidence for hydrocarbon generation. Under proper conditions, the Mesoproterozoic mat-rich carbonates will have the potential for hydrocarbon generation and serve as source rocks. On the basis of petrified biomats, a rough estimation suggests that the Mesoproterozoic carbonates of the North China platform might have a hydrocarbon production potential in theorder of 10×108t. 相似文献
11.
南海东沙西南海域冷泉碳酸盐岩特征及其意义 总被引：9，自引：2，他引：7
海底冷泉流体或自生碳酸盐沉积可为碳氢化合物(主要指常规油气或天然气水合物)、冷泉生物群落的调查和研究提供有利线索。对东沙群岛海区、神狐海区和ODP184-1146钻孔碳酸盐沉积的特征进行了对比和研究,结果表明这些海区碳酸盐岩的岩性特征、碳氧同位素组成等存在明显差异。东沙群岛海区和神狐海区的碳酸盐岩的化学成分如TFe、A l2O3、TiO2、K2O、Na2O、MnO、P2O5等不同,表明它们可能分别受到了粘土矿物和铁锰氧化物影响。在神狐海区至少发生了一次冷泉流体活动,形成了早晚两期冷泉碳酸盐岩,而在东沙群岛海区发生了至少3次冷泉流体活动,形成了多期冷泉碳酸盐岩,反映了这两个海区碳酸盐沉积的甲烷成因不同,且形成环境也受不同的因素控制。研究揭示,在东沙群岛南部海区可能发育热成因甲烷汇聚的天然气水合物,其海底可能存在冷泉生物群落,这为东沙西南海域天然气水合物和冷泉生物群落的进一步寻找和研究提供了新思路。 相似文献
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自生碳酸盐矿物是揭示甲烷渗漏过程及其周期性变化的重要指标。为了方便、快速地识别出自生碳酸盐矿物,在探讨了前人建立的端元组分模型(文石、高镁方解石、生物成因方解石和碎屑)在我国南海北部适用性的基础上,利用沉积物全样中Sr/Ca和Mg/Ca值计算了南海北部神狐海域两支沉积物柱状样中自生碳酸盐矿物的质量分数,计算结果表明,在不同沉积深度均有含量不等的自生碳酸盐矿物。这一结果被X射线衍射结果和沉积物中存在晶形完好的自生高镁方解石和文石矿物所验证,表明利用前人建立的端元组分模型计算的结果具有可靠性。自生碳酸盐矿物的出现显示该海域深受甲烷渗漏作用影响。利用地球化学指标(Sr/Ca和Mg/Ca)获得的自生碳酸盐矿物含量垂向变化显示该区域甲烷渗漏具有强弱交替的周期变化。运用端元组分模型来获取沉积物柱状样中自生碳酸盐矿物的高分辨率剖面,从而识别甲烷渗漏信息非常方便,在大范围寻找甲烷渗漏和天然气水合物方面具有较大潜力。 相似文献
13.
极低碳稳定同位素是识别地质历史时期古冷泉及其甲烷释放事件的关键证据,目前,世界范围内尚无有关二叠纪冷泉活动的直接证据报道。本研究首次报道了西藏地区拉萨地块早二叠世碳酸盐岩的极低碳同位素数据,δ13CV-PDB值最低可达-34.69‰,碳、氧稳定同位素呈现较好的负相关性,指示为甲烷厌氧氧化作用成因。该碳酸盐岩发育于西藏申扎地区下二叠统昂杰组上段(碎屑岩段),以透镜状碳酸盐岩夹层及碳酸盐质胶结结核产出,可见方解石结晶扇,其碳同位素普遍较结核中碳酸盐胶结物更贫13C。推测研究区存在早二叠世古甲烷冷泉渗漏活动,其成因可能与冈瓦纳冰期后温暖海水导致的海洋甲烷水合物藏的失稳释放有关。作为研讨地质历史时期水合物-冰期反馈模型的重要实例,本研究对进一步探讨冰期海平面变化、古海洋化学、古生态和古气候等特殊环境变化事件具有重要的指示意义。 相似文献
14.
Authigenic Gypsum in Gas-Hydrate Associated Sediments from the East Coast of India (Bay of Bengal) 总被引：2，自引：0，他引：2
M. KOCHERLA 《《地质学报》英文版》2013,87(3):749-760
Authigenic gypsum crystals, along with pyrite and carbonate mineralization, predominantly calcites were noticed in distinct intervals in a 32 m long piston core, collected in the gas hydrate- bearing sediments in the northern portion of the Krishna-Godavari basin, eastern continental margin of India at a water depth of 1691 m. X-ray diffraction and energy dispersive spectrum studies confirm presence of pyrite, gypsum, calcite, and other mineral aggregates. The occurrence of gypsum in such deep sea environment is intriguing, because gypsum is a classical evaporite mineral and is under saturated with respect to sea water. Sedimentological, geochemical evidences point to diagenetic formation of the gypsum due to oxidation of sulphide minerals (i.e. pyrite). Euhedral, transparent gypsum crystals, with pyrite inclusions are cemented with authigenic carbonates, possibly indicating that they were formed authigenically in situ in the gas hydrate-influenced environment due to late burial diagenesis involving sulphate reduction and anaerobic oxidation of methane (AOM). Therefore, the authigenic gypsums found in sediments of the Krishna-Godavari and Mahanadi offshore regions could be seen as one of the parameters to imply the presence of high methane flux possibly from gas hydrate at depth. 相似文献
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16.
《China Geology》2020,3(1):16-27
Bottom simulating reflector (BSR) has been recognized as one of the indicators of gas hydrates. However, BSR and hydrate are not one-to-one correspondence. In the Xisha area of South China Sea (SCS), carbonate rocks wildly develop, which continuously distribute parallel to the seafloor with high amplitude on seismic sections, exhibiting reflections similar to BSRs in the Shenhu area nearby. This phenomenon causes some interference to hydrates identification. In this paper, the authors discussed the typical geophysical differences between carbonate rocks and hydrates, indicating that the main difference exists in relationship between porosity and velocity, causing different amplitude versus offset (AVO) characters. Then the authors proposed a new model assuming that the carbonates form the matrix and the hydrate fill the pore as a part of the matrix. The key modeling parameters have been optimized constrained by P-velocities and S-velocities simultaneously, and the model works well both for carbonate rock and gas hydrate bearing sediments. For quantitative identification, the authors calculated the velocities when carbonates and hydrates form the matrix together in different proportions. Then they proposed a carbonate and hydrate identification template (CHIT), in which the possible hydrate saturation (PHS) and possible carbonate content (PCC) can be both scaled out for a group of sample composed by P-velocity and S-velocity. If PHS is far larger than PCC, it is more likely to be a hydrate sample because carbonates and hydrates do not coexist normally. The real data application shows that the template can effectively distinguish between hydrates and carbonate rocks, consequently reducing the risk of hydrate exploration. 相似文献
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18.
LIU Liping SUN Zhilei ZHANG Lei WU Nengyou Yichao Qin JIANG Zuzhou GENG Wei CAO Hong ZHANG Xilin ZHAI Bin XU Cuiling SHEN Zhicong JIA Yonggang 《《地质学报》英文版》2019,93(3):731-755
Natural gas hydrates have been hailed as a new and promising unconventional alternative energy, especially as fossil fuels approach depletion, energy consumption soars, and fossil fuel prices rise, owing to their extensive distribution, abundance, and high fuel efficiency. Gas hydrate reservoirs are similar to a storage cupboard in the global carbon cycle, containing most of the world’s methane and accounting for a third of Earth’s mobile organic carbon. We investigated gas hydrate stability zone burial depths from the viewpoint of conditions associated with stable existence of gas hydrates, such as temperature, pressure, and heat flow, based on related data collected by the global drilling programs. Hydrate-related areas are estimated using various biological, geochemical and geophysical tools. Based on a series of previous investigations, we cover the history and status of gas hydrate exploration in the USA, Japan, South Korea, India, Germany, the polar areas, and China. Then, we review the current techniques for hydrate exploration in a global scale. Additionally, we briefly review existing techniques for recovering methane from gas hydrates, including thermal stimulation, depressurization, chemical injection, and CH4–CO2 exchange, as well as corresponding global field trials in Russia, Japan, United States, Canada and China. In particular, unlike diagenetic gas hydrates in coarse sandy sediments in Japan and gravel sediments in the United States and Canada, most gas hydrates in the northern South China Sea are non-diagenetic and exist in fine-grained sediments with a vein-like morphology. Therefore, especially in terms of the offshore production test in gas hydrate reservoirs in the Shenhu area in the north slope of the South China Sea, Chinese scientists have proposed two unprecedented techniques that have been verified during the field trials: solid fluidization and formation fluid extraction. Herein, we introduce the two production techniques, as well as the so-called “four-in-one” environmental monitoring system employed during the Shenhu production test. Methane is not currently commercially produced from gas hydrates anywhere in the world; therefore, the objective of field trials is to prove whether existing techniques could be applied as feasible and economic production methods for gas hydrates in deep-water sediments and permafrost zones. Before achieving commercial methane recovery from gas hydrates, it should be necessary to measure the geologic properties of gas hydrate reservoirs to optimize and improve existing production techniques. Herein, we propose horizontal wells, multilateral wells, and cluster wells improved by the vertical and individual wells applied during existing field trials. It is noteworthy that relatively pure gas hydrates occur in seafloor mounds, within near-surface sediments, and in gas migration conduits. Their extensive distribution, high saturation, and easy access mean that these types of gas hydrate may attract considerable attention from academia and industry in the future. Herein, we also review the occurrence and development of concentrated shallow hydrate accumulations and briefly introduce exploration and production techniques. In the closing section, we discuss future research needs, key issues, and major challenges related to gas hydrate exploration and production. We believe this review article provides insight on past, present, and future gas hydrate exploration and production to provide guidelines and stimulate new work into the field of gas hydrates. 相似文献
19.
南海台西南区碳酸盐岩矿物学和稳定同位素组成特征——天然气水合物存在的主要证据之一 总被引：29，自引：0，他引：29
南海台西南区是中国南海中天然气水合物赋存的最有利场所。研究表明,该区的碳酸盐岩主要以结壳、烟囱的形式出现,结壳的裂隙或孔洞中常常充填有淡黄-白色的文石晶体。碳酸盐岩中自生碳酸盐矿物主要为文石、高镁方解石,少量白云石、铁白云石和菱铁矿。扫描电子显微镜(SEM)分析表明,文石主要呈针状、长柱状、放射束状,高镁方解石呈颗粒状。碳酸盐岩的碳同位素δ13C值主要在-56·878‰~-32·829‰PDB之间,大多数小于-40‰PDB,显示了生物甲烷成因碳源的特征;氧同位素δ18O值在2·1875‰~5·045‰PDB之间,主要在4‰PDB以上,这种较重的氧同位素比值表明,天然气水合物分解产生的富18O水体可能是碳酸盐岩沉淀的流体源。矿物学和碳氧稳定同位素研究表明,南海台西南区的碳酸盐岩为细菌性甲烷成因碳酸盐岩,可能与天然气水合物有关,显示了该区水合物存在的可能性很大。 相似文献
20.
Marine gas hydrate and cold-seep systems, which maintain a large amount of methane in the seabed, may critically impact the geochemical and ecological characteristics of the deep-sea sedimentary environment. However, it remains unclear whether marine sediments associated with gas hydrate harbor novel microbial communities that are distinct from those from typical marine sediments. In this study, microbial community structures thriving in sediments associated with and without gas hydrate in the eastern Japan Sea were characterized by 16S rRNA gene-based phylogenetic analyses. Uncultivated bacterial lineages of candidate division JS1 and a novel group NT-B2 were dominant in the sediments from gas hydrate-associated sites. Whereas, microbial populations from sites not associated with gas hydrate were mainly composed of Bacteroidetes, Nitrospirales, Chlamydiales, Chlorobiales, and yet-uncultured bacterial lineages of OD1 and TM06. The good correlation between the dominance of JS1 and NT-B2 and the association of gas hydrate could be attributed to the supply of more energetically favorable energy sources in gas-rich fluids from the deep subsurface than refractory organic matter of terrigenous and diatomaceous origin. 相似文献