Karst phenomena with gas emanations in Early Oligocene conglomerates: risks within a highway context (Jura,Switzerland)

During the construction of the A16 motorway, four cavities were discovered in the Early Oligocene carbonate conglomerates of the Jura mountains, northwest Switzerland. One cavity was particularly interesting because of its size and gas emanations. Previous geological works carried out in this key area are summarized, notably the effects of tectonic evolution on the formation of karstic networks. The methods used for the exploration and study of the principal cavity are described. The tectonic and lithological influence on the spelaeogenesis of the network; the natural and/or anthropic origin of the gas emanations and the implications of the cavities for the highway construction are discussed.      

塔里木盆地玉北地区孢粉组合及时代讨论

通过对塔里木盆地玉北地区8口钻井324块孢粉样品的分析鉴定数据进行系统整理,在区块内泥盆系-古近系建立了9个孢粉组合。孢粉组合特征表明,产孢粉地层时代为晚泥盆世-渐新世。孢粉组合的建立和时代的讨论使之与精细地层研究工作相适应,为地层划分和时代确定提供了生物地层学依据,从而更好地服务于生产实践。     

COMPOSITION OF DIAMONDOIDS IN OIL SAMPLES FROM THE ALPINE FORELAND BASIN,AUSTRIA: POTENTIAL AS INDICES OF SOURCE ROCK FACIES,MATURITY AND BIODEGRADATION

Twenty‐seven oil samples from Cretaceous, Eocene and Rupelian reservoir rocks in the Alpine Foreland Basin (Austria) were analysed to evaluate the composition of diamondoid hydrocarbons using gas chromatography – triple quadrupole mass spectrometry. The oils were generated from marly and shaly Oligocene source rocks buried beneath the nappes of the Alpine foldbelt to the south of the study area. Diamondoid hydrocarbons were detected in the saturated fraction of all the analysed oils. A biodegraded oil sample from a shallow reservoir in the NE part of the study area showed an enrichment in diamondoids due to the molecule's high resistance to microbial degradation. Variations in the organic matter type of the source rock facies and differences in maturity are known to influence the composition of diamondoids. However in this study, biomarker‐derived maturity parameters do not show a convincing correlation with diamondoid maturity parameters. Moreover, no cracking trend based on biomarkers and diamondoid concentrations was observed. The results indicate that the composition of diamondoids in oils from the Austrian part of the Alpine Foreland Basin is mainly controlled by heterogeneities in the Lower Oligocene source rocks, including the occurrence of a redeposited source rock succession in the western part of the study area. By contrast, EAI‐1 (the ethyladamantane index) shows a good correlation with various maturity parameters and seems to be independent of source rock facies.     

东非鲁武马盆地渐新统深水沉积层序地层格架组成和时空分布

由于缺乏与陆架边缘的直接联系,深水层序划分在层序地层学研究中成为难点。东非鲁武马盆地渐新统含气砂岩储层为深水沉积环境的重力流沉积,合理的层序地层划分方法可以指导有利目标层系的解释及区域油气勘探。以混合层序地层模型为指导,以三维地震资料应用为主,多种资料综合分析开展深水层序地层学研究,揭示渐新统深水沉积过程和沉积体系的成因联系。根据地层的终止类型、凝缩段、块体搬运沉积等识别层序边界,通过分析沉积物性质、规模以及形成深水沉积的浊流密度差异,确定沉积结构单元与体系域的对应关系,建立渐新统等时地层格架,分析深水沉积演化规律。鲁武马盆地渐新统划分为两个三级层序,强制海退的早期在近陆架边缘陆坡上均形成大规模局部发育的块体搬运沉积,之后在不同层序沉积特征表现出差异性。下渐新统三级层序以粗-中粗砂岩为主、具有高砂/泥比、高密度的大型朵体为强制海退晚期产物。堤化水道体系沉积于低位体系域及海侵早期,顶部为凝缩段沉积,使下渐新统层序具有完整体系域组成;受研究区数据范围影响,上渐新统三级层序缺少大型朵体,层序内缺少下降期体系域晚期沉积,其他体系域内沉积结构单元与下渐新统具有较好的相似性。     

珠江口盆地晚渐新世陆架边缘三角洲沉积层序结构及演化

南海北部上渐新统珠海组广泛发育外陆架-陆架边缘三角洲和深水斜坡扇体系，它们构成了区内最为重要的油气储层。综合地震、测井、岩心等资料，研究了珠海组陆架边缘三角洲及前三角洲斜坡扇的层序结构、沉积成因类型、沉积演化及控制作用。珠海组为一个复合层序，其内可进一步分为4个层序。通过追踪坡折点变化建立了滨岸迁移轨迹，划分了各层序内的沉积成因单元（水进、略上行正常水退、明显上行正常水退、局部下行强制性水退等）。外陆架三角洲以发育厚约100~150 m的前积层为特征，地震上多表现为切线型反射结构；而陆架边缘三角洲前缘-斜坡复合前积层厚达200~1 000 m，具S型、切线斜交型等地震反射结构，以发育厚层的三角洲前缘砂坝和大规模的滑塌变形堆积为特征，并与前三角洲-斜坡扇共生。研究区可识别出6套三角洲前积体，其面积具有逐渐变大、并沿走向扩展的趋势。区内晚渐新世层序的发育受到海平面变化的控制，区域性沉积旋回还受到构造沉降作用叠加的影响。大量沉积物的供给和区域性海平面下降是导致陆架边缘三角洲和前三角洲斜坡扇广泛发育的主控因素。     

琼东南盆地深水区中央坳陷带东部渐新统烃源岩分布及评价

琼东南盆地深水区是中国海上油气勘探的前沿阵地和油气资源接替的重要战略选区,而确定烃源岩分布特征是深水区低勘探领域石油地质研究的首要任务。在预测及确定中央坳陷带东部渐新统烃源岩厚度、成熟度和有机相等分布特征的基础上,通过计算烃源岩体积、生气量、生气强度等,完成了烃源岩的综合评价,最终实现了富生烃凹陷的优选。研究表明:①整体上,陵水组烃源岩厚度大于崖城组,其中崖二段和陵二段为烃源岩最为发育的层段,同时泥岩沉积中心表现出从西向东、从崖城组零星分布到陵水组统一连片的演化趋势;②烃源岩热演化呈现西早东晚、现今成熟度呈现西高东低的趋势;③渐新统烃源岩质量整体较好,其中煤层为优质烃源岩,泥岩为中等—好烃源岩;崖城组主要有机相为浅海相和滨海相,而陵水组主要有机相为内、外浅海相;④宝岛凹陷、长昌凹陷和松南凹陷均达到富生气凹陷级别,但前者综合评价为最好级别,后两者则分别为较好和一般。     

有线电视网带电的特殊故障

有线电视网带电的特殊故障□谭大勋（贵州省石阡县广播电视局５５５１００）图１今年６月，县有线电视出现一个怪毛病，每到中午１２点和晚上８点左右，全县大部分用户的电视机上都有同样一种现象——两条黑白相间的横带在电视机屏幕上缓慢上下移动，时而场不同步，特别是...     

渤海中部渐新世以来强烈沉陷的区域构造条件

渤海中部属于北华北新生代裂陷盆地(渤海湾盆地)东部的渤中坳陷,渐新世以来沉降深达10000余m,是我国少有的富生烃地区.渤中坳陷的主体部分位于北西向的北京—蓬莱和北北东向的郯庐2条区域性断裂带交汇区的西北象限,同时也是盆地东部伸展—拉分构造系统的拉分构造部位.深部存在北东向地幔隆起,地壳厚度为27～28km,构造背景复杂而独特.渐新世以来,北京—蓬莱断裂带左旋走滑、营口—潍坊断裂带右旋走滑和盆地东部伸展拉分构造系统活动各自产生的局部拉张应力作用的叠加,以及深部地幔上隆的联合作用,致使渤海中部自渐新世以来发生强烈沉降.     

The main controlling factors and developmental models of Oligocene source rocks in the Qiongdongnan Basin, northern South China Sea

Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but with strong heterogeneity. Through the analysis of trace elements,organic macerals and biomarkers, it is indicated that plankton has made little contribution to Oligocene source rocks compared with the terrestrial higher plants. The organic matter preservation depends on hydrodynamics and the redox environment, and the former is the major factor in the study area. During the sedimentary period of the Yacheng Formation, tidal flats were developed in the central uplift zone, where the hydrodynamic conditions were weak and the input of terrestrial organic matter was abundant. So the Yacheng Salient of the central uplift zone is the most favorable area for the development of source rocks, followed by the central depression zone. During the sedimentary period of the Lingshui Formation, the organic matter input was sufficient in the central depression zone due to multiple sources of sediments. The semi-enclosed environment was favorable for organic matter accumulation, so high quality source rocks could be easily formed in this area, followed by the Yacheng salient of central uplift zone. Source rocks were less developed in the northern depression zone owing to poor preservation conditions.     

冷湖七号和南八仙渐新统混积岩储层特征对比分析

渐新统下干柴沟组下段是柴北缘中部地区油气勘探的主要目标,弄清该区储层发育的控制因素是深入评价的基础。文中根据铸体薄片、普通薄片及岩屑录井等资料,时该区冷湖七号和南八仙构造的岩石学特征进行了对比分析。研究表明,该区大量发育陆源碎屑、碳酸盐、硬石膏的混合沉积．但是由于水体成度的不同。在冷湖七号的滨浅湖混积岩中硬石膏含量较高,颗粒主要为基底式胶结;而南八仙构造地处辫状河三角洲前缘相带,因河流的稀释作用,混积岩中硬石膏体积分数很低,颗粒为孔隙式．基底式钙质胶结,原生孔喉较为发育,有利于后期酸性流体的溶蚀改造。由于2种类型混积岩的初始孔隙度及孔喉演化模式不同,最终引起2个地区含油气丰度的巨大差异。