Reservoir characterization of Scollard-age fluvial sandstones,Alberta foredeep

A detailed laboratory study of 53 sandstone samples from 23 outcrops and 156 conventional core samples from the Maastrichtian-Paleocene Scollard-age fluvial strata in the Western Canada foredeep was undertaken to investigate the reservoir characteristics and to determine the effect of diagenesis on reservoir quality. The sandstones are predominantly litharenites and sublitharenites, which accumulated in a variety of fluvial environments. The porosity of the sandstones is both syn-depositional and diagenetic in origin. Laboratory analyses indicate that porosity in sandstones from outcrop samples with less than 5% calcite cement averages 14%, with a mean permeability of 16 mD. In contrast, sandstones with greater than 5% calcite cement average 7.9% porosity, with a mean permeability of 6.17 mD. The core porosity averages 17% with 41 mD permeability. Cementation coupled with compaction had an important effect in the destruction of porosity after sedimentation and burial. The reservoir quality of sandstones is also severely reduced where the pore-lining clays are abundant (>15%). The potential of a sandstone to serve as a reservoir for producible hydrocarbons is strongly related to the sandstone’s diagenetic history. Three diagenetic stages are identified: eodiagenesis before effective burial, mesodiagenesis during burial, and telodiagenesis during exposure after burial. Eodiagenesis resulted in mechanical compaction, calcite cementation, kaolinite and smectite formation, and dissolution of chemically unstable grains. Mesodiagenesis resulted in chemical compaction, precipitation of calcite cement, quartz overgrowths, and the formation of authigenic clays such as chlorite, dickite, and illite. Finally, telodiagenesis seems to have had less effect on reservoir properties, even though it resulted in the precipitation of some kaolinite and the partial dissolution of feldspar.     

Chemostratigraphy of upper Jurassic reservoir sandstones,Danish Central Graben,North Sea

A chemostratigraphic study of Upper Jurassic sandstones in the northern Danish Central Graben has been undertaken within the framework of a well-defined stratigraphic/sedimentological model based particularly on cored well sections. Two reservoir sandstone units are recognised, the transgressive marginal marine to shoreface sandstone of the Gert Member and the regressive to transgressive shoreface sandstone of the Ravn Member. Both members belong to the Heno Formation, which is equivalent to the Fulmar Formation (UK) and the Ula Formation (Norway).     

Turbidite-reservoir architecture in complex foredeep-margin and wedge-top depocenters,Tertiary Molasse foreland basin system,Austria

We employ an integrated subsurface dataset, including >400 m of drill cores and three-dimensional (3D) seismic-reflection data from >530 km² of the Tertiary Molasse foreland basin system in Austria, to characterize turbidite-system architecture across structurally complex foredeep-margin and wedge-top depocenters and to interpret the influence of tectonic deformation and submarine topography on hydrocarbon-reservoir quality and distribution. Turbidite-system architecture and depositional processes were correlated with associated topographic features in order to identify zones of preferential sediment gravity-flow convergence or divergence. Zones of flow convergence facilitate flow acceleration and accumulative flow behavior, whereas zones of flow divergence facilitate deceleration and depletion. Zones of preferential flow convergence include narrow (<2 km) and steep (<20°) foredeep-margin slope channels along thrust front-segmenting tear faults, and steep, unchannelized piggyback-basin and foredeep margins (local gradients as great as 40° across piggyback-basin margins). The foredeep-margin gradient is exaggerated principally by tectonic deformation that post-dates turbidite-system development, based on a paucity of growth strata. Piggyback-basin-margin gradients are exaggerated as a result of deformation synchronous with and following turbidite-system development, judging from the presence of growth strata. Slope-channel topography facilitated the development of relatively coarse-grained, amalgamated turbidite reservoirs, whereas unchannelized basin-margin topography facilitated deposition of fine-grained, chaotic non-reservoirs. Zones of preferential flow divergence are flat (<1°), unconfined (i.e., large in comparison to sediment gravity flows) piggyback-basin floors, which facilitated the development of relatively coarse-grained, non-amalgamated, upward fining turbidite reservoirs, stratigraphically partitioned by fine-grained mass transport-complex deposits. The results of this study elucidate the influence of foredeep-margin and wedge-top tectonic deformation and topography on turbidite-system and associated reservoir character and distribution across the Molasse foreland basin system in Austria, and can be applied to oil and gas exploration in analogous, structurally complex settings.     

Bacterial methane in the Atzbach-Schwanenstadt gas field (Upper Austrian Molasse Basin), Part I: Geology

Bacterial methane gas accumulations occur in Upper Oligocene to Early Miocene clastic deepwater sediments in the Austrian Molasse Basin. Methane gas is produced from the Upper Puchkirchen Fm. (Aquitanian) in the Atzbach-Schwanenstadt gas field which is one of the largest gas fields in this basin.     

流动单元研究进展

提高油藏描述的精度、确定剩余油的分布、改善开发效果的关键是认识油藏的非均质性。介绍了一种研究油藏非均质性的新方法——流动单元研究方法的国内、国外研究进展及流动单元的概念、各种研究方法和流动单元研究的应用,并提出了针对大型陆相油田、非均质性较强的储层流动单元划分方法设想。     

三峡水库澎溪河水-气界面CO2、CH4扩散通量昼夜动态初探

三峡水库温室气体效应近年来备受关注.为揭示三峡水库典型支流澎溪河水-气界面CO₂和CH₄通量的昼夜动态规律,明晰短时间尺度下该水域温室气体释放的影响因素,在2010年6月至2011年5月的一个完整水文周年内,选择4个具有代表性的时段(2010年8、11月和2011年2、5月)对澎溪河高阳平湖水域开展昼夜跟踪观测.结果表明:2010年8、11月和2011年2、5月4次采样的CO₂日总通量值分别为-8.34、73.94、28.13和-20.12 mmol/(m²·d),相应的CH₄日总通量值分别为2.22、0.11、0.32和7.16 mmol/(m²·d),不同时期昼夜变化明显.研究水域CO₂和CH₄通量过程不具同步性:CO₂昼夜通量变化可能更显著地受到水柱光合/呼吸过程的影响,但瞬时气象过程(水汽温差、瞬时风速等)在高水位时期亦可对CO₂通量产生显著影响;CH₄昼夜通量变化与水温条件改变更为密切.     

三峡水库与长寿湖水库鱼类碳、氮稳定同位素特征及营养级的比较

为探究人为活动对水库鱼类食物来源和营养级关系的影响,选择人为影响程度较低的三峡水库和影响程度较高的长寿湖水库为研究对象,应用碳、氮稳定同位素技术对两个水库鱼类δ¹³C值、δ¹⁵N值和营养级进行比较分析.结果显示：长寿湖水库鱼类δ¹³C平均值（-22.66‰±1.94‰）与三峡水库（-22.59‰±1.87‰）较为接近,但长寿湖鱼类的δ¹⁵N值（13.95‰ ±3.02‰）显著高于三峡水库鱼类的δ¹⁵N值（11.98‰ ±2.25‰）.根据δ¹⁵N值计算不同食性鱼类间的营养级,三峡水库营养级为肉食性鱼类 > 杂食性鱼类 > 浮游生物食性鱼类 > 草食性鱼类;而长寿湖中则表现为浮游生物食性鱼类 > 肉食性鱼类 > 杂食性鱼类 > 草食性鱼类,营养级出现了异常现象.这一结果表明,对于人为影响（如人工喂食鱼饲料等）较大的水体,采用δ¹⁵N值计算不同食性鱼类间的营养级存在不确定性.     

太湖与广东汤溪水库微囊藻gyrB基因序列分析

测定了江苏太湖和广东汤溪水库7株铜绿微囊藻(M.aeruginosa)和1株水华微囊藻(M.flos-aquae)gyrB基因部分序列(974bp),发现40个变异位点,17个简约信息位点,平均(G+C)%为47.8%,序列间相似性≥97.10%.在NJ分子系统树上,不同种类的微囊藻混杂分布,表明基因型聚类与表型无直接关系;不同地理来源的铜绿微囊藻间遗传变异小,没有明显的地理聚群,反映出地理差异并不影响遗传上的相似性;支持暂将不同藻种归为铜绿微囊藻复合种的分类处理.gyrB基因对微囊藻遗传差异的解析效果优于16S rRNA,与16S-23S ITS和cpcBA-IGS等效果相当,表明gyrB基因可能成为研究微囊藻分类和遗传变异新的良好分子标记.     

中国东南丘陵山区水质良好水库现状与天目湖保护实践

东南丘陵山区是我国水库分布最为集中的区域之一,这些水库在保障区域供水安全方面具有极其重要的作用,应该优先保护.然而,水库水环境保护正面临丘陵山区开发强度持续增加,开发方式和空间布局不合理,氮、磷污染及富营养化趋势严峻,缺乏完善监测和管理体系等众多问题.本文以2000年以来天目湖水库保护实践过程为例,从库体水环境治理、流域污染物削减和综合管理3个方面介绍天目湖沙河水库保护的措施和成效,在此基础上提出良好湖库优先保护的建议:建立具有部门协调能力的水库管理机构,实行基于湖库水生态目标的水质目标管理,治理丘陵山区茶果园的面源污染,注重流域生态系统整体的恢复,禁止上游水源涵养区和临湖地带的开发,划定生态保护红线,明确禁止和限制的开发类型与规模,加强湖库及流域的监测和预警,开展必要的水库水体治理工程,并针对性地制定湖库管理条例.天目湖十几年的保护实践中有效地解决了流域开发与水库水质保护之间的矛盾,使天目湖水质由快速恶化转为稳步好转,为东南丘陵山区经济发展过程中水库的环境保护探索了一条道路.     

分层异重流背景下降雨对三峡水库香溪河水华消退的影响

为探究在三峡水库特殊分层异重流背景下降雨对水华消退的影响,以香溪河为例,对库湾降雨前后水动力、生态环境因子开展连续三维立体跟踪监测。结果表明:降雨对水华的消退作用显著,降雨后香溪河库湾叶绿素a(Chl.a)浓度明显下降。热分层稳定指数(RWCS/H)变化不大,库湾近河口处分层较弱、中上游分层较强的特性并未随此次降雨发生较大变动。受降雨影响,藻类在表层水体聚集程度降低,藻类聚集度指数(MI)、微藻群体平均深度(MRD)下降。库湾流态随降雨发生而变得复杂,库湾水体浊度明显增加,异重流倒灌形式由近表层倒灌向中下层倒灌转变,雨后又逐渐转变为中层倒灌,长江干流水体倒灌进入库湾的影响范围、潜入深度增加。水体水平输移增强,分散下沉的藻类易随水体环流流出库湾,水华消退。雨后库湾入库流量增加,大部分上游来流依旧由上层流向河口,与中层倒灌异重流形成逆时针环流,藻类无法在表层水体稳定生长,库湾Chl.a浓度能在较长时间内保持较低水平,不会再次迅速暴发水华。