海底天然气渗漏形成水合物量的线性动力学模型:以墨西哥湾GC185区块Bush高地为例

世界许多地区如墨西哥湾，存在着大量天然气渗漏并形成水合物的现象，出于科学，生态，气候和安全的需要。人类有必要弄清存在于海底以水合成形式存在的天然气的比例。因此，构建了水合物形成量的线性动力学模型，以分析墨西哥湾GC185块区Bush高地海底渗漏天然气的地质过程和行为。Bush高地渗漏的天然气来源于附近的Jolliet气藏，结果表明，渗漏天然气中约有9％的海底形成了水合物。     

天津地区主要河流表层沉积物中饱和烃的组成与分布特征

根据不同环境功能区 9条河流表层沉积物样品中饱和烃污染物的分析结果,讨论了天津地区河流沉积物中饱和烃化合物的组成与分布特征,初步分析了饱和烃污染物的污染源.结果表明,不同河流表层沉积物中均分布有多种类型的饱和烃化合物,主要包括正构烷烃、无环类异戊二烯烷烃、异构与反异构烷烃、烷基环己烷和甾、萜类等.不同河流及同一河流不同河段的表层沉积物中可抽提有机物(EOM)、烃类化合物含量和饱和烃化合物的组成特征均存在明显的差别,其中北塘排污河(北排污河)和大沽排污河(南排污河)沉积物中 EOM的含量相对较高,海河及津北地区的潮白新河、蓟运河、永定新河、北京排污河的沉积物中 EOM的含量相对较低;北运河、南运河及大沽排污河巨各庄河段的沉积物中烃类化合物含量相对较高,海河、大沽排污河和北塘排污河表层沉积物中烃类污染物的含量相对较低.位于市区北部的河流,靠近市区的河段沉积物中 EOM含量有增加的趋势,而位于市区下游的河流,靠近市区的上游河段的沉积物中 EOM含量相对较高,下游河段的有所降低.河流中烃类污染物主要来源于矿物油及其衍生物、高等植物蜡和藻类的降解产物,不同河流及相同河流不同河段污染源的相对贡献存在明显的差别.     

长江口水下三角洲表层沉积物有机质分布特征

根据对长江口水下三角洲31个表层样沉积物粒度、总有机碳(TOC)、总氮(TN)的测定,得出了粒度及有机质的分布特征,利用C/N比分析有机质来源及不同来源的贡献率。研究结果表明: 1)长江口水下三角洲表层沉积物平均粒径介于3~8Φ之间,存在由陆向海变细的趋势; 2)TOC含量在0.1% ~1.2% 之间,平均值为0.52%; TN含量介于0.02% ~0.08% 之间,平均值为0.057% 。TOC和TN含量的分布特征相似,具有自陆向海、由低至高的变化趋势,这主要是受到沉积物粒径的影响,但是TOC在崇明岛东侧和九段沙东侧有两个高值点,可能与人类活动或局地因素有关; 粒度校正之后,TOC含量在0.40% ~1.67% 之间,平均值为0.68%; TN的含量介于0.05% ~0.10% 之间,平均值为0.07% 。TOC含量在近岸地区略高,TN含量是北部地区略高于南部地区,并且TOC和TN都在崇明岛东侧和九段沙东侧有两个高值点; 3)C/N比值在6~16之间,平均值为9.6; 利用C/N比值估算得到的陆源有机碳含量在35% ~90% 之间,平均值为60% 。C/N比和陆源有机碳含量在长江口南支外围邻近海域表层沉积物中较高,表明南支带来了大量的陆源有机质入海,并呈舌状向东北方向凸出; 而在长江北支附近其值相对较低,表明北支径流影响相对减弱,潮流作用相对增强。研究表明,长江南支是主要的陆源有机质入海通道,而进入水下三角洲之后陆源有机碳分布受到了河口混合过程的显著影响。     

ODP184航次岩芯海底沉积物元素相态研究及其对有机质和轻烃的指示意义

分析了ODP184航次1 146站位海底岩芯沉积物中的Cu、Fe、Ni等7种元素的总量和相态分布及变化规律;研究发现,各元素的总量及相态的剖面分布受生物作用、有机质络合吸附、共沉淀等多种因素控制;沉积物主要来自陆源.元素Cu、Co、Ni的有机结合态及总量的分布规律表明深部地层中存在大量有机物;结合岩芯沉积物中有机气体及相关地质背景,认为该区具有良好的油气赋存条件;对各元素的相态与轻烃及各有机指标进行聚类分析,发现虽然可交换态的Cu、Fe、Ni在元素各相态中所占的比例较少,但却是指示油气存在的有效指标.     

南极半岛西北海域表层沉积物中微植物有机质分布特征及其意义

南极半岛西北海域表层沉积特中，微植物有机质颗粒包括五种类型：现代孢粉、再沉积孢粉、具结构有机质残骸、无结构有机质颗粒以及海藻类。按成因可分为陆生物质和海生物质两大类。本文分析陆生微植物有机质、特别是再沉积孢粉和无结构有机颗粒的组分、丰度、时代及分布格局，指出区内表层沉积物可能属于近源补给成因，半岛陆架、南设德兰群岛岛架和岬湾等的水动力条件强于海峡中央，并探讨了物源与海流的关系。     

哈素海沉积物中氮和有机质的分布特征

针对哈素海富营养化日趋严重的现实,系统开展了湖泊沉积物中不同形态氮及有机质的空间分布和污染特征研究。结果表明,表层沉积物中TN、Org N、NH+4 N及有机质的水平分布均表现经向分异特征,Org N的分布特征主导了TN的水平分布格局,有机质与TN具有强相关性。沉积柱芯中TN随深度增加而递减,有机质和Org N与TN的垂向分布相似,尽管 NH+4 N的垂直变化分异较大,但仍表现于表层富集的特点。Org N为表层沉积物和沉积柱芯中氮的主导形态,NH+4 N为无机氮的主导形态,成岩过程中,沉积物中TN只有极少部分在发生矿化。沉积物中有机质主要来源于湖中芦苇等大型挺水植物及陆源输入。哈素海表层沉积物的氮污染对底栖生物已经产生了严重的生态毒性效应,对底栖生物群落及整个水生生态系统构成了严重威胁。     

南黄海中部表层沉积物有机质分布与分子组成研究

通过分析南黄海中部501个站位表层沉积物通沉积物有机质、粒度及常量元素特征,了解有机质分布特征及影响因素,并进一步对其中64个站位的进行气相色谱（GC-FID）分析,探讨有机质分子组成。分析表明:南黄海中部总有机碳受水动力影响呈分布西低东高分布,总有机碳与Al2O3含量中值粒径依次相关特性;正构烷烃组成表明有机质主要来源于陆源高等植物,海洋浮游藻类贡献次之,陆源植物中草本植物与木本植物贡献相当,类异戊二烯烃反映了短链正构烷烃明显海洋还原沉积环境;常量元素与正构烷烃参数综合分析表明,南黄海中部陆源有机质主要来自于现代黄河、苏北古黄河输入,体现无机-有机综合分析对有机质物源判断;部分样品具有明显石油源输入特征,细菌对沉积物有机质贡献普遍存在。     

祁连山七一冰川区表层沉积物中生物标志化合物的组成特征及来源研究

利用GC和GC—MS的分析方法,对祁连山七一冰川冰雪不溶微粒、冰尘和七一冰川流域表层土壤中的烷烃、脂肪酸、脂肪酸甲酯和长链酯、酮以及多环芳烃等生物标志化合物进行了分析,研究了它们的组成和分布特征,讨论了它们的环境地球化学意义。结果表明,生物标志化合物分布特征组成和分布特征指示了七一冰川地区的有机质具有藻类、高等植物、化石燃料燃烧产物等多种来源。冰雪不溶微粒和七一冰川流域表层土壤中有机物的来源相似,且这两种介质中的有机污染物种类多于冰尘,表明快速的工业化已经对七一冰川及其周围环境产生明显影响。     

南祁连盆地木里冻土区第四纪沉积物中可溶有机质的来源及其与天然气水合物的关系

在南祁连盆地木里坳陷钻遇中国陆域第一例天然气水合物实物样品。通过对木里冻土区钻遇水合物区域（DK井区）第四纪沉积物及邻区湖相沉积物中可溶有机质开展有机地球化学分析,发现DK井区浅地表沉积物中明显存在热解成因的可溶有机质,而邻区老人湖湖相沉积物中可溶有机质以高等植物输入为主。与区内烃源岩对比,热解成因的可溶有机质主要来源于中侏罗世烃源岩,晚三叠世尕勒得寺组烃源岩也有一定的贡献。结合该区水合物气源研究成果,DK井区沉积物中可溶有机质与形成水合物的烃类气体可能属于同源,侏罗纪、三叠纪烃源岩热演化生成的烃类能够沿断裂、砂岩裂隙等通道向上运移或渗漏至浅地表,其中甲烷、重烃气等轻质组分能够在稳定带内与地层水结合形成天然气水合物。木里地区第四纪沉积物中可溶有机质的来源解析能够为天然气水合物的勘探提供新的视角。     

海底表层沉积物中苯系物含量对海域油气指示作用研究

国内外研究表明钻井岩心和海底沉积物样品中单环芳烃(BTEX)指标异常与油气藏直接相关并具有高分辨、高精度特征,是有价值的油气地球化学勘探指标;但由于较深沉积物样品的采集与检测技术成本较高,限制了BTEX指标在海域油气化探工作中的推广应用。本文利用渤海北部辽东湾海域浅海的表层沉积物,通过热解析与气相色谱技术方法对其苯系物含量的特征开展研究。数据分析结果表明,在油气藏和生油凹陷上方的苯系物含量总体高于凹陷外样品,尤其是对二甲苯和间二甲苯均表现出明显差异,表明表层沉积物中的苯系物含量对生烃凹陷具有一定的指示作用。本文证实了利用表层沉积物中BTEX含量预测含油气前景区的有效性,热解析气相色谱检测苯系物含量方便快捷,减小了采样成本和分析成本,显示该技术方法在海域油气化探领域具有良好的应用前景。通过对苯系物含量异常点的分析表明,在沿岸及张性断裂上方BTEX含量出现异常高值,显示人类活动以及断裂构造对表层沉积物中的苯系物含量有明显影响,因此实际工作中应结合地质特征和其他化探指标综合分析,以降低单一化探指标的多解性。     

Oil seepage and carbonate formation: A case study from the southern Gulf of Mexico

Oil seeps from the southern Gulf of Mexico can be regarded as natural laboratories where the effect of crude oil seepage on chemosynthesis‐based communities and carbonate precipitation can be studied. During R/V Meteor cruise 114 the seep sites UNAM (Universidad Nacional Autónoma de México) Ridge, Mictlan Knoll and Tsanyao Yang Knoll (Bay of Campeche, southern Gulf of Mexico) were investigated and sampled for authigenic carbonate deposits containing large amounts of liquid oil and solid asphalt. The δ¹³C values of individual carbonate phases including: (i) microcrystalline matrix aragonite and calcite; (ii) grey, cryptocrystalline to microcrystalline aragonite; and (iii) clear, fibrous aragonite cement, are between ?30‰ and ?20‰, agreeing with oil as the primary carbon source. Raman spectra reveal that residual heavy oils from all sites are immature and most likely originate from the same reservoir. Geochemical batch modelling using the software code PHREEQC demonstrates how sulphate‐driven oxidation of oil‐derived low‐molecular to high‐molecular weight hydrocarbons affects carbonate saturation state, and shows that the oxidation state of carbon in hydrocarbon compounds and oxidation rates of hydrocarbons control carbonate saturation and precipitation at oil seeps. Phase‐specific trace and rare earth element contents of microcrystalline aragonite and calcite, grey cryptocrystalline aragonite and clear aragonite were determined, revealing enrichment in light rare earth elements for grey aragonite. By comparing trace element patterns of carbonates with those of associated oils, it becomes apparent that liquid hydrocarbons constitute an additional source of trace metals to sedimentary pore waters. This work not only demonstrates that the microbial degradation of oil at seeps may result in the precipitation of carbonate minerals, it also elucidates that trace metal inventories of seep carbonates archive diagnostic elemental patterns, which can be assigned to the presence of heavy hydrocarbons in interstitial pore waters.     

Total mercury and methylmercury in sediments near offshore drilling sites in the Gulf of Mexico

Concentrations of total Hg in sediments near six drilling sites in the Gulf of Mexico were elevated well above average background values of 40–80 ng/g. The excess Hg was associated with barite from discharged drilling mud. In contrast with total Hg, concentrations of methylmercury (MeHg) in these sediments did not vary significantly at nearfield (<100 m) versus farfield (>3 km) distances from the drilling sites. Observed variability in concentrations of MeHg were related to local differences in redox state in the top 10 cm of sediment. Low to non-detectable concentrations of MeHg were found in nearfield sediments that were anoxic, highly reducing and contained abundant H₂S. At most drilling sites, nearfield samples with high concentrations of total Hg (>200 ng/g) had similar or lower amounts of MeHg than found at background (farfield) stations. Higher values of MeHg were found in a few nearfield sediments at one site where concentrations of TOC were higher and where sediments were anoxic and moderately reducing. Overall, results from this study support the conclusion that elevated concentrations of MeHg in sediments around drilling sites are not a common phenomenon in the Gulf of Mexico.     

Pyritization of Iron in Sediments from the Continental Slope of the Northern Gulf of Mexico

In sediments from the continental slope of the Northern Gulf of Mexico, generally,the degree of iron pyritization (DOP) is low (<0.1) and dissolved sulfide is belowdetection limits (5 M), whereas dissolved Fe is typically about 50 to100 M. Therefore, the dissolution of kinetically reactive iron minerals generallydominates over the rate of sulfide production in sediments throughout this region.However, in sediments where hydrocarbons have been added via seepage from thesubsurface, dissolved-Fe is undetectable, DOP can approach 1, and high concentrationsof dissolved sulfide (up to 11 mM) are commonly present. Even though thesesediments have high total reduced sulfide (TRS) concentrations (typically 150 to370 mol gdw^-1), their average C/S ratio is about 4 times that of normal marine sediments reflecting the major input of hydrocarbons. DOP is significantly (20%) higher when calculated using reactive-Fe extracted by citrate dithionite than by cold 1N HCl. This difference is primarily due to the greater extraction efficiency of the cold HCl method for silicate-Fe. TRS tends to rise to a maximum, and remains close to constant even at high (mM) dissolved sulfide concentrations. These TRS concentrations, therefore, represent the size of the ``kinetically' reactive-Fe pool during early diagenesis.     

微生物、有机质、油气与砂岩型铀矿①

统计表明,世界上已知重要的砂岩型铀矿床的含矿主岩不同程度地含有机质、微生物或油气。对十红滩矿床、努和廷矿床及512矿床进行有机岩石学、有机地球化学、铀与有机碳相关关系分析等研究结果表明,微生物、有机质或油气在砂岩型铀矿成矿的过程中起了重要的作用。     

Spatial trends in the geochemical composition of sediments in the Panuco River discharge area, Gulf of Mexico.

Major and trace elements, organic matter, carbonates, loss of ignition, grain size, gravel, sand, silt, clay, and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy (February), dry (May), and rainy (September) seasons in the coastal area adjacent to Panuco River discharges into the Gulf of Mexico. The sediments supplied by the river move in a north-east direction, and are deposited in the north-east extreme of the studied area. Terrigenous sediments show a strong association of Al₂O₃ with Fe₂O₃, Na₂O, K₂O, P₂O₅, Rb, Cu, Zn, organic matter, clay, and grain size (Mz). Mineralogical analysis shows that they are formed by quartz, kaolinite, montmorillonite, illite-montmorillonite and biotite. The highest metal concentration of Cu (25 mg/kg), Zn (155 mg/kg), Pb (50 mg/kg) and organic matter (1.26%) was observed in the sampling points located very close to the river mouth. A statistical analysis was done with the information contained in the variables. Five significant factors explain 77% of the total variance: factor 1 is due to sediments from a terrigenous source, factor 2 corresponds to sediments from a biogenous source, factor 3 is associated to sediments with heavy minerals, factor 4 is due to Co concentration, and factor 5 is due to Ni concentration. The sediments supplied from the river had a short-term local impact on the sediment distribution, as observed by the carbonate and heavy mineral concentration of the sediments.     

微生物、有机质、油气与砂岩型铀矿

统计表明，世界上已知重要的砂岩型铀矿床的含矿主岩不同程度地含有机质、微生物或油气。对十红滩矿床、努和廷矿床及512矿床进行有机岩石学、有机地球化学、铀与有机碳相关关系分析等研究结果表明，微生物、有机质或油气在砂岩型铀矿成矿的过程中起了重要的作用。     

准噶尔盆地东北缘航空高光谱油气微渗漏探测及地质验证

准噶尔盆地东北缘乌伦古坳陷油气成藏潜力巨大,目前其勘探工作较少,亟待低成本,高效率,大面积的油气普查,以圈定潜在油气勘探靶区。利用航空高光谱数据,结合野外实测光谱,提取研究区油气微渗漏引起的烃类及相关蚀变矿物信息。结果显示,研究区的油气渗漏异常区具有环带状分布特征。野外查证发现,部分异常区具有地表晕环状分带、粘土化、碳酸盐化和植被中毒等油气渗漏相关的地质特征。渗漏的烃类以层状、条带状、斑点状和吸附式等四种形式富集地表。油气以烃分子形式沿断裂、裂缝等通道垂向逸散,具有"烟囱效应"。研究区油气渗漏受控于断层、不整合面和揉皱构造等。结合区域构造演化史和油气成藏史,认为研究区大规模的油气渗漏可能开始于燕山期,在喜山期达到渗漏高峰。并认为研究区中部隆起带具有较好的油气成藏潜力,是下一步油气勘探的重点区域。     

祁连山冻土区天然气水合物烃类气体组分 的特征和成因

祁连山冻土区天然气水合物DK-2科学钻探试验孔水合物储集层岩心气样的烃类气体组分和C同位素分析测试结果表明,祁连山冻土区天然气水合物烃类气体组分复杂,除甲烷外,还含有较高的乙烷和丙烷;δ13C1均大于-50‰,R值普遍小于100,显示出明显的热解气特征。结合钻探区的地质背景和岩性特征,初步判断气体大多来源于深部迁移上来的油型气,并有部分原地煤成气的混合。     

广西北部湾北缘晚古生代一新生代油气资源潜力探讨

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