抚仙湖水生植物HCO3-利用效率及与之相关的内源有机碳沉积通量研究

因可能是全球"遗失碳汇"的重要组分,耦合生物碳泵效应的碳酸盐风化碳汇日益受到学界关注,并且其对不同时间尺度上的气候变化都可能产生重要影响。由碳酸盐风化产生的HCO3-能否形成稳定的碳汇尚缺乏足够论证,厘清这一问题的关键在于如何有效评估水生植物固定HCO3-的能力,尤其是植物残体进入沉积物后的实际碳固定量。本文基于已发表的抚仙湖数据,利用碳同位素端元模型估算了抚仙湖水生植物光合固定HCO3-碳量,发现无机碳源中约有57%是以HCO3-的形式被水生植物光合固定下来,碳汇通量达24.76 tC/(km2·a)。而可能由于微生物分解等作用,抚仙湖现代沉积物中真正被埋藏下来的内源有机碳沉积通量,即耦合生物碳泵效应的碳酸盐风化碳汇通量仅为9.2~16.4 tC/(km2·a),这大致相当于水生植物所固定HCO3-的一半。尽管如此,水生植物的光合作用和碳酸盐风化耦合作用仍表现出巨大的碳汇潜力。因此,在未来的全球碳循环和气候变化模型中需考虑碳酸盐风化碳汇的影响。     

Soil seed bank longevity of the exotic annual grass Bromus rubens in the Mojave Desert,USA

Although arid environments are often considered among the least invaded terrestrial biomes, the impacts of exotic plant species can be severe and long lasting. Bromus rubens (red brome) is an exotic annual grass species in the Mojave Desert known to outcompete native plant species, alter habitat, and promote accumulation of fuel that contributes to increasing fire frequency and severity. We assessed longevity of the exotic B. rubens seeds in the soil by burying seeds at four depths (0, 2, 5, and 10 cm) and recovering seeds 6, 12, 18, and 24 months after burial. Seed viability was reduced with greater burial depth and greater time since burial. A relatively small proportion of seeds retained viability for two years, suggesting that while the B. rubens seed bank can be large, it is relatively short-lived. Although B. rubens apparently relies more on the annual production, dispersal, and germination of seeds than on a long-lived seed bank for its annual recruitment, the numerous seeds produced by individual plants indicate that even a small proportion of seeds remaining viable for more than a year can aid recruitment from the seed bank and is an important factor in understanding population dynamics.     

Fault‐controlled dolomite bodies as palaeotectonic indicators and geofluid reservoirs: New insights from Gargano Promontory outcrops

The Upper Jurassic to Lower Cretaceous platform‐slope to basinal carbonate strata cropping out in Gargano Promontory (southern Italy) are partly dolomitized. Fieldwork and laboratory analyses (petrographic, petrophysical and geochemical) allowed the characterization of the dolomite bodies with respect to their distribution within the carbonate succession, their dimensions, geometries, textural variability, chemical stability, age, porosity, genetic mechanisms and relation with tectonics. The dolomite bodies range from metres to kilometres in size, are fault‐related and fracture‐related, and probably formed during the Early Cretaceous at <500 m burial depths and temperatures <50°C. The proposed dolomitization model relies on mobilization of Early Cretaceous seawater that flowed, downward and then upward, along faults and fractures and was modified in its isotopic composition moving through Triassic and Jurassic strata that underlie the studied dolomitized succession. Despite the numerous cases reported in literature, this study demonstrates that hydrothermal and/or high‐temperature fluids are not necessarily required for fault‐controlled dolomitization. Distribution and geometries of dolomite bodies can be used for palaeotectonic reconstructions, as they partly record the characteristics (size, attitude and kinematics) of the palaeo‐faults, even if not preserved, that controlled dolomitization. In Gargano Promontory, dolomites record Early Cretaceous palaeo‐faults from metres to kilometres long, striking north‐west/south‐east to east/west and characterized by normal to strike‐slip kinematics. Dolomitization increases the matrix porosity by up to 7% and, therefore, can improve the geofluid storage capacity of tight, platform‐slope to basinal limestones. The results have a great significance for characterization of geofluid (for example, hydrocarbons) reservoirs hosted in similar dolomitized carbonate successions. Distribution, size and shapes of reservoir rocks (i.e. dolomite bodies) could be broadly predictable if the characteristics of the palaeo‐fault system present at the time of dolomitization are known.     

深埋藏条件下鲕粒灰岩的热水交代实验研究

在相对静岩压力40 MPa、地温150℃(大体相当于4 000 m深埋条件)、用时15 d的条件下,对灰色中厚层状鲕粒灰岩进行深埋藏热水交代白云化实验研究。结果表明:反应前后岩石的结构发生了轻微变化,尾液中的主要化学成分Ca2+浓度从0 mg/L增加到337 mg/L,Mg2+浓度从过饱和溶液降低到2 830 mg/L。电子探针分析结果表明,固体样CaO含量由61.000%降为60.830%,而MgO则由0.296%升到0.350%。可见,参与实验的固、液样品反应前后主量元素Ca、Mg有一定的变化。但根据样品的宏观观察、镜下鉴定、扫描电镜及X衍射图谱的综合对比,认为在该实验条件下,尚未产生明显的白云化现象。     

轮南奥陶系潜山表层岩溶储层的分布特征

轮南古潜山位于塔里木盆地塔北隆起轮南低凸起中部地区,主要岩溶层位是奥陶系鹰山组与一间房组,轮南古潜山的形成条件和表生岩溶作用时间与中国南方的桂林岩溶存在极其相似之处。本文通过研究轮南地区古风化壳表层岩溶带发育分布特征及其形成影响因素,认为:表层岩溶带主要分布于距古风化面以下0～40m范围内,此带范围内岩溶缝洞系统相对比较发育,岩溶缝洞系统具有一定连通性,属岩溶储层较为发育的部位,岩溶储层有效储集空间主要是溶蚀孔洞、小规模溶洞和溶蚀裂缝;表层岩溶带发育与古岩溶地貌及古水动力条件具有密切关系,岩溶地貌类型或水动力条件不同,表层岩溶带发育厚度、岩溶形态与岩溶缝洞系统发育规模、岩溶缝洞系统充填特征也不同。      

埕岛油田海底天然气管道掩埋状况勘测及其影响因素分析

以胜利埕岛油田海底长输天然气管道为例，较系统介绍了海底管道勘测方法，根据调查资料成果，划分了调查地区地貌特征类型，给出了天然气埋设探测状况，总结了水深变化规律和区域水深差异特点，分析了水深变化、海底冲蚀和地质作用等因素对海底管道可能造成的影响，为管道安全生产、灾害预报评估和今后海上工程调查研究提供参考。     

南极普里兹湾沉积物中有机碳和总氮的含量与分布

利用中国多次南极科学考察获得的沉积物样品,对普里兹湾沉积物中有机碳(OC)、总氮(TN)的含量和分布以及OC/TN进行了分析。结果表明:普里兹湾表层沉积物中OC和TN的含量变化范围分别为0.14%~1.20%和0.02%~0.20%,平均值分别为0.63%和0.11%。OC/TN的变化范围为5.5~8.2,平均值为6.8。OC和TN含量呈现明显的正相关性,表明有机质来源相同,比值接近6.6,说明有机质主要为海洋生源沉积。两者平面分布趋势非常一致,且与沉积物中泥质含量呈显著正相关,湾内73°E以西区域OC和TN含量较低,而以东区域含量较高,这是上层水体生产过程和冰川携带陆源砂等因素共同作用的结果。垂直分布上,OC和TN含量总体上表层高于深层,OC含量随深度增加逐渐降低,达到一定深度后趋于稳定。较高的沉积速率加速OC的埋藏,5根柱样中OC的埋藏率为39%~91%,平均为66%,表明普里兹湾是重要的碳汇区。     

四川盆地三叠系飞仙关组气藏储层成岩作用研究拾零

近年来在四川盆地三叠系飞仙关组鲕粒白云岩储层中发现的高含硫天然气三级储量已近1×1012 m3。鲕粒白云岩储层集中分布在含蒸发岩的层序中,储层中有残余石膏、硬石膏及它们的模孔、方解石铸模（假象）等,表明白云石化流体与蒸发海水有关。白云石化由层间古暴露面向下增强的成岩层序说明这种白云石化是成岩早期发生的,并可能有大气降水与蒸发海水混合的影响。白云岩样品各结构组分氧、碳同位素微区测试数据差别显著,这说明采用岩石混合样做研究白云石化成因的地球化学分析可能导致误解。飞仙关组的白云岩中多数保存了原岩结构幻影、结构残余或原岩的全部结构说明白云石化过程是等体积交代。白云岩储层中的孔隙是各种溶蚀孔而非白云石化等摩尔交代的体积收缩孔。飞仙关组高含硫气藏储层中沥青和溶蚀孔的关系表明深埋晚期溶蚀孔最发育。在溶液中碳酸的电离常数大大高于氢硫酸,飞仙关组高含硫气藏天然气组分中的CO2相对于H2S的质量亏损和储层中有富轻碳的高温方解石充填晚期溶孔、裂缝表明储层中的晚期溶解作用是由硫酸盐热还原过程（TSR）中生成的CO2引起的。     

沙埋对河西走廊4种旱生植物种子萌发和幼苗生长的影响

测定了驼蹄瓣(Zygophyllum fabago)、骆驼蒿(Peganum nigellastrum)、唐古特白刺(Nitraria tangutorum)和黒果枸杞(Lycium ruthenicum)等4种旱生植物种子重量、形状、萌发及活性,试验了沙埋深度(0、1、2、3、4、5 cm)对种子萌发、幼苗出土和生长的影响。结果表明:4种植物的种子扩散时为中度休眠;种子活性与重量、形状之间为显著负相关关系(p<0.05);种子初次萌发率与重量之间为不显著负相关关系;大而不规则种子有较低的活性,小种子扩散时有较高萌发率。随沙埋深度的增加,4种植物种子出苗率下降,首次出苗时间推迟,茎高、绝对株高和根长呈现先上升后下降的趋势,地下和地上生物量比值呈先上升后下降或随埋深增加而下降。幼苗出土和生长的最佳沙埋深度是:驼蹄瓣1~3 cm,骆驼蒿0~1 cm,唐古特白刺0~2 cm,黑果枸杞1~2 cm。在植被恢复过程中应考虑破除种子休眠的方法以及浅层沙埋等条件,以提高出苗率、增大幼苗定植率。     

鄂尔多斯盆地奥陶系不同组构碳酸盐岩埋藏溶蚀实验

鄂尔多斯盆地奥陶系碳酸盐岩储层受埋藏溶蚀作用控制明显,而地层深部复杂的水-岩反应造成埋藏溶蚀研究难度较大,并进而影响了储层的评价与预测。分别利用CO₂溶液和乙酸溶液为流体介质进行溶蚀模拟实验,探讨埋藏条件下温度、压力、流体等因素对不同矿物及组构碳酸盐岩溶蚀作用的影响。结果表明:1）随着温度与压力升高,碳酸盐岩样品在乙酸溶液中的溶解速率均相应提高,在CO₂溶液中的溶解速率则先增加后减小,且在110℃~130℃区间内溶蚀速率最大;深埋藏环境下,各岩类溶蚀速率差异减小,并趋于一致;2）岩石矿物成分和组构,原岩初始孔隙度的大小及其连通关系,以及晶体的产状对成岩后期的埋藏溶蚀作用也具有重要的影响。不溶组分含量低、颗粒/灰泥比高、矿物成分复杂的碳酸盐岩由于组构选择性溶蚀作用而更易被溶蚀;碳酸盐岩的溶蚀速率随方解石含量的增加而增加,但深埋藏环境下,矿物成分含量差异对溶蚀速率的影响作用减弱;硬石膏与白云岩相伴生时,可优先溶蚀形成膏模孔,并促进白云石的溶解,改善储层效果。不同岩性,总体上灰岩较白云岩及过渡岩类更易发生埋藏溶蚀作用。结合研究区实际地质条件分析,砂屑灰岩、膏质白云岩等埋藏溶蚀强度较大,通过对原岩早期组构选择性溶蚀形成孔隙的继承和调整,叠加埋藏期岩溶作用后,可形成规模优质储层。