Oil migration driven by exhumation of the Canol Formation oil shale: A new conceptual model for the Norman Wells oil field,northwestern Canada

Thermal history, petroleum system, structural, and tectonic constraints are reviewed and integrated in order to derive a new conceptual model for the Norman Wells oil field, and a new play type for tectonically active foreland regions. The thermal history recorded by Devonian rocks suggests that source rocks experienced peak thermal conditions in the Triassic–Jurassic, during which time oil was likely generated. After initial oil generation and expulsion, the Canol Formation oil shale retained a certain fraction of hydrocarbons. The shallow reservoir (650–350 m) is a Devonian carbonate bank overlain by the Canol Formation and resides within a hanging wall block of the Norman Range thrust fault. Both reservoir and source rocks are naturally fractured and have produced high API non-biodegraded oil. Thrust faults in the region formed after the Paleocene, and a structural cross-section of the field shows that the source and reservoir rocks at Norman Wells have been exhumed by over 1 km since then.The key proposition of the exhumation model is that as Canol Formation rocks underwent thrust-driven exhumation, they crossed a ductile–brittle transition zone and dip-oriented fractures formed sympathetic to the thrust fault. The combination of pore overpressure and new dip-directed subvertical fractures liberated oil from the Canol Formation and allowed for up-dip oil migration. Reservoir rocks were similarly fractured and improved permeability enhanced charging and pooling of oil. GPS and seismicity data indicate that strain transfer across the northern Cordillera is a response to accretion of the Yakutat terrane along the northern Pacific margin of North America, which is also the probable driving force for foreland shortening and rock exhumation at Norman Wells.     

桑沟湾农药残留及贝毒对海洋环境质量影响和主要食用贝类健康风险评估

根据2009-04—2010-02隔月6个航次桑沟湾9个调查站位贝类养殖区有机氯(OCPs)、有机磷(OPPs)农药残留和麻痹性贝毒(PSP)的调查资料,分析了它们在该海域海水中、表层沉积物中和主要贝类(栉孔扇贝、太平洋牡蛎和菲律滨蛤仔)体内的含量水平,就农药残留及贝毒污染对海洋环境质量的影响进行综合评价和类别划分,并对主要食用贝类中农药残留和贝毒的暴露水平进行健康风险评估。结果表明,桑沟湾贝类养殖区海水质量、沉积物质量和养殖贝类质量水平范围为1~2级,平均分别为2级、1级和1级,养殖生态环境综合质量水平为2级;总体上,该海域海洋环境综合质量处于良好水平,贝类产区生态环境质量为1类区(清洁区)。即该海域农药残留及贝毒污染对海洋环境质量影响较小或无明显影响。另外,针对食用桑沟湾贝类水产品的消费人群进行了农药残留及贝毒污染的健康风险评估,结果表明调查人群食用贝类中OCPs中的HCHs和DDTs、OPPs中的马拉硫磷和甲基对硫磷、PSP的日摄入量分别为0.75,2.11,0.19,0.09和1.22μg/(人·d),其摄入量低于ADI的推荐限值,因此桑沟湾主要食用贝类中农药残留及贝毒污染的健康风险处于安全范围。     

石油烃和营养盐的复合污染对海洋浮游植物的影响Ⅰ. 石油烃对海洋浮游植物吸收营养盐的影响

通过向具有相同营养盐浓度的培养体系中添加不同浓度的石油烃,对中肋骨条藻、赤潮异弯藻、微小亚历山大藻和锥状斯氏藻进行周期性培养,探讨了石油烃对微藻营养盐吸收动力学的影响.结果发现,在开始30min内,微藻对营养盐均有一非耗能的短暂快吸收,随后吸收速率下降并趋于稳定.石油烃对中肋骨条藻和赤潮异弯藻氮、磷的吸收都表现抑制作用,浓度从0.13 mg/L到8.25mg/L的石油烃所呈现的抑制作用基本表现为先减弱后逐渐增强,8.25mg/L浓度的石油烃抑制作用最强.与中肋骨条藻和赤潮异弯藻实验结果不同的是,石油烃对微小亚历山大藻和锥状斯氏藻的氮、磷吸收在低浓度时呈现促进作用,且促进作用的程度随石油烃浓度的增加有先增强后减弱的趋势,在高浓度下促进作用会消失,8.25mg/L的石油烃不表现促进作用.石油烃对微藻营养盐吸收动力学的影响表现出复杂性,这既受石油烃浓度的影响,也与浮游植物的种类有重要关系.     

试论火山岩油气藏成藏机理

全球100多个国家/地区在火山岩内或其周围发现了油气藏或油气显示,展示了火山岩油气藏勘探的广阔前景。火山岩已从油气勘探的"禁区"转变为了"靶区",成为油气勘探的新目标。火山岩储集物性较好,其本身可直接作为储层,各类侵入体与围岩相互作用还可形成与火成岩有关的圈闭。火山岩油气藏的烃源包括有机成因和无机成因两种。火山作用可以明显提高烃源岩内有机质的成熟度,加快烃的产生,促进油气运移,并为无机成因烃提供合成原料(CO_2和H_2等)和运移通道。虽然火山岩在盆地早期尤为发育,约占盆地充填体积的1/4,但是目前火山岩油气储量仅占世界油气探明储量的1%左右,勘探潜力巨大。中国沉积盆地内发育不同时代火山岩,火山岩储层与烃源岩匹配较好,无机成因气来源丰富,火山岩油气藏正在成为我国油气勘探的重要领域之一。     

胶洲湾5 种海藻中的多不饱和脂肪酸与有机氯农药共摄入风险的评估研究

海藻中含有丰富的多不饱和脂肪酸(PUFA),但同时也富集一定浓度的有机氯农药,食用海藻摄入多不饱和脂肪酸的同时也会摄入这类污染物,其共摄入风险分析评估是食品安全领域必须关注的科学问题。本文以胶州湾近岸采集的条斑紫菜、坛紫菜、海带、裙带菜、龙须菜等5种常见经济海藻为研究对象,分析了其脂肪酸和有机氯农药组成情况。结果表明,这5种海藻中脂肪酸以棕榈酸、油酸、亚油酸、花生四烯酸和二十碳五烯酸(DHA)为主,n-6和n-3 PUFA的比值远小于建议值4,均有较高的营养价值;5种海藻中六六六类农药主要残留的是γ-HCH,滴滴涕类农药中P,P’-DDD、P,P’-DDT残留量较高。对PUFAs中的有效成分二十碳五烯酸(EPA)+DHA与有机氯农药污染物共摄入时对人体的益害风险进行了评估,发现对于健康成人在达到EPA+DHA摄入要求下,食用这5种海藻带来的多不饱和脂肪酸与有机氯农药污染物共摄入引起非致癌或致癌的健康风险较低。     

Marine hydrocarbon source rocks of the Upper Permian Longtan Formation and their contribution to gas accumulation in the northeastern Sichuan Basin,southwest China

Identification of the main hydrocarbon source rocks of the large Puguang gas field (northeastern Sichuan Basin, southwest China) has been the subject of much discussion in recent years. A key aspect has been the lack of a comprehensive understanding of the development of hydrocarbon source rocks of the Upper Permian Longtan Formation, which had been thought to contain mainly coal seams and thick carbonate layers. In this paper, based on geological data from more than ten wells and outcrops and their related mineralogy and geochemistry, we investigated the depositional environment and main factors controlling organic matter enrichment in the Longtan Formation. We propose a model which combines information on the geological environment and biological changes over time. In the model, organic matter from prolific phytoplankton blooms was deposited in quiescent platform interior sags with rising sea-levels. During the Longtan period, the area from Bazhong to Dazhou was a platform interior sag with relatively deep water and a closed environment, which was controlled by multiple factors including syngenetic fault settling, isolation of submarine uplifts and rising sea-levels leading to water column stratification. Although the bottom water was anoxic, the phytoplankton were able to bloom in the well-lit upper euphotic zone thus giving rise to a set of sapropelic black shales and marlstones containing mostly algal organic matter with minor terrestrial contributions. As a consequence, these rocks have a high hydrocarbon generation potentials and can be classified as high-quality source rocks. The area from Bazhong to Dazhou is a center of hydrocarbon generation, being the main source of reservoired paleo-oils and presently discovered as pyrobitumen in the Puguang gas field. The identification of these source rocks is very important to guide future petroleum exploration in the northeastern Sichuan Basin.     

Quantitative characterization of connectivity and conductivity of sandstone carriers during secondary petroleum migration,applied to the Third Member of Eocene Shahejie Formation,Dongying Depression,Eastern China

Studies on migration pathways remain qualitative, albeit extensive quantification of migration forcing. In this study, hydrocarbon carriers are defined as carrier units and their corresponding carrier beds for the Third Member of Eocene Shahejie Formation in the Dongying Depression, Bohai Bay Basin, eastern China, on the basis of their lithofacies and physical properties, spatial relationships, and data availability; secondary migration conduits are then quantified. A carrier unit is defined as a stratigraphic unit that contains microscopically porous and permeable carrier beds and is covered by regional seals. The carrier beds are macroscopically and physically connected to each other within a carrier unit and are hydrodynamically connected during secondary migration. A method of quantifying sandstone carrier units using common physical properties is developed. First, a carrier unit containing potential carrier beds is identified on the basis of lithofacies and their lateral changes. Second, physical connectivity of sandstone carrier beds is assessed on the basis of percolation theory. Third, the hydrodynamic connectivity of a sandstone carrier unit is analyzed using effective parameters that may reflect the hydraulic circulation in the carrier unit. Last, the conductivity of a sandstone carrier bed is quantitatively characterized using appropriate physical property parameters. The results for sandstone carrier units in the Third Member of the Shahejie Formation are used in numerical models addressing Pleistocene secondary migration. The model results explain the discovered accumulation and hydrocarbon shows well; and the model predictions on exploration targets have been confirmed by drilling.     

因子分析在海河流域石油类污染综合评价中的应用(英文)

基于因子分析对2012~2013年海河流域pH、DO、COD、BOD5、氨态氮和总石油烃等6项水质指标的监测数据进行统计,并对其中四项指标进行水污染综合指数评估,旨在对海河水质进行较为系统的评价。结果显示,BJ1和HB2两个站位水质属于Ⅳ类标准,其余各站位均为Ⅴ类;各站位综合评价结果得到海河流域指数为1.44,说明海河流域处于污染状态,其污染程度超过该流域功能区的标准。因子分析发现,COD、DO和NH3-N之间差异显著(P0.05);主成分分析显示,除pH和BOD5外,其余指标都在0.70以上;COD、DO、NH3-N和TPH的贡献率较高,其中总石油烃的贡献率为100%,因此可以认为该海域的污染类型属于有机污染,且石油烃污染较为突出。     

List of members of the Editorial Board

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