Diet composition and overlap for adult walleye,lake whitefish,and yellow perch in Green Bay,Lake Michigan

Interspecific interactions among walleye Sander vitreus, lake whitefish Coregonus clupeaformis, and yellow perch Perca flavescens in Green Bay could influence the population status of each species, but potential trophic interactions are poorly understood. Our objectives were to determine if diet assemblages for each species and diet overlap among species varied spatially and temporally within Green Bay. Adult walleye (≥381 mm total length (TL); N = 981), lake whitefish (≥432 mm TL; N = 1507), and yellow perch (≥150 mm TL; N = 1174) were collected during May-October of 2018 and 2019 from multiple locations in southern and northern Green Bay. Diet assemblages of each species varied between northern and southern Green Bay, but walleye diets were more temporally variable (among months within zones and between years) than diets of lake whitefish or yellow perch. Lake whitefish represented a seasonally important prey item for walleye in southern Green Bay, composing 10 % and 41 % of walleye diets by weight in May and June, respectively. Yellow perch generally composed <15 % of walleye diets by weight but were consumed at a broader spatiotemporal scale than lake whitefish. Diet overlap between walleye and both lake whitefish and yellow perch was generally weak or moderate, whereas diet overlap between whitefish and perch was generally strong. Our assessment of adult trophic interactions suggests that changes in the population status of one species could influence fisheries for all three, and we identify additional research questions to address potential population-level effects of these trophic interactions.     

汉江上游干支流沉积物细菌群落多样性和影响因素

为了解汉江上游干支流沉积物细菌多样性以及确定性过程和随机性过程在沉积物细菌群落构建过程中的相对重要性,基于Illumina高通量测序技术,分析了环境因子对细菌群落组成的影响,采用非度量多维尺度(NMDS)排序探究了季节之间沉积物细菌群落的差异,并结合中性群落模型和标准化随机率量化了确定性过程和随机过程对群落构建的影响。结果表明:汉江上游及其支流细菌群落主要由变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、蓝藻门(Cyanophyta)、浮霉菌门(Planctomycetes)和酸杆菌门(Acidobacteria)等组成；细菌群落在不同季节有显著差异；地理距离和环境因子对细菌群落结构影响较小,确定性过程并未在细菌群落组成中起到主导作用；随机过程很大程度上影响了群落在秋季和春季的组成,是沉积物细菌群落构建的主导因素。     

珠江口盆地珠一坳陷古近系高自然伽马砂岩形成机制及油气地质意义

运用放射性元素寻找油气是一种非常规油气勘探手段。近年来,在珠江口盆地珠一坳陷富烃凹陷周边古近系钻遇高自然伽马(GR)砂岩,其GR值(100~300 API)甚至大于同区泥岩的GR值(100~200 API)。为了弄清该特殊现象背后的地质意义,对珠江口盆地珠一坳陷古近系高自然伽马砂岩开展了铀(U)、钍(Th)、钾(K)等3种元素含量与GR值的相关趋势线分析,从井震特征、岩性特征及矿物成分特征等入手分析了砂岩GR值增高的主要原因及成因机制,探讨了放射性元素聚集的条件、运移通道、驱动力以及油气意义。结果表明:西江、惠州地区由U含量增高导致砂岩GR值偏高,恩平、番禺地区由K,Th含量增高导致砂岩GR值偏高;砂岩GR值增高有两大成因机制,一是地下流体带来的放射性元素离子U4+在氧化-还原面处富集后导致地层GR值偏高,这种特殊现象说明在具有连通基底大断裂旁的圈闭中,U4+的富集指示了曾经油气的存在,证实了研究区油气运移通道的有效性,对于油气藏的预测有着非常重要的指导性意义,二是地表流体带来的含放射性元素的矿物大量沉积后导致地层GR值偏高,含放射性元素矿物性质不稳定,可指示近源供给的存在,对于判断物源及沉积环境有着非常重要的意义。该研究成果为预测研究区油气成藏有利区带提供了依据。     

利比亚古达米斯盆地含油气系统研究

利比亚古达米斯盆地是一个巨大的撒哈拉台地克拉通内盆地，该盆地对于利比亚乃至北非都是一个重要的含油气盆地，对于整个非洲大陆油气的形成和储集具有重要影响。在分析盆地地质构造特征和沉积演化特征的基础上，进一步探讨了盆地烃源岩、储集层和盖层的演化发育历史形态，并对盆地内2个较为重要的含油气系统进行了剖析，为在该盆地内进一步开展石油勘探开发工作提供了可靠依据。     

高泉背斜地层压力测井多参数综合解释与异常高压成因

目前国内外地层压力测井解释方法较多,但大多数方法基于欠压实沉积理论并局限于单一的地层岩性,尤其是针对盆地边缘山前深层构造,单一测井参数确定地层压力误差较大,且无法解释沉积压实机制以外的异常高压。为此,将多种异常高压机制相关的测井参数进行综合解释,建立适合山前复杂构造的地层压力测井多参数计算模型,评价准噶尔盆地南缘高泉背斜高探1井的地层压力剖面,其计算结果与钻井实测数据吻合,相对误差小于3.00%.同时,基于原始沉积加载—卸载过程力学原理,利用地层压力测井多参数分析判别出高泉背斜深层各层系异常高压的形成机制。     

秋里塔格构造带盐下构造层变形特征及油气勘探潜力

秋里塔格构造带位于库车坳陷中部,受南天山造山作用的影响,发育一系列冲断构造,具明显的分层变形特征。依据地面露头和地震资料,秋里塔格构造带以古近系库姆格列木群及新近系吉迪克组膏盐岩为中心,可划分为盐上构造层、膏盐岩构造层和盐下构造层;受挤压作用,膏盐岩差异流动,在地表形成多排线性褶皱带,盐上构造层则发育逆冲推覆及反冲构造,而盐下构造层的变形特征主要受控于挤压应力和古生代古隆起,具有明显的分段性。中秋—东秋段位于新和—牙哈古隆起北坡,盐下构造层发育与克深构造带相似的冲断构造,可形成幅度高、规模较大的断背斜圈闭,油气勘探潜力大;佳木—西秋段位于温宿和西秋古生代古隆起之上,盐下构造层不发育冲断构造,盐下圈闭以低幅度断背斜和断块为主,规模不大,勘探潜力相对较小。     

不同脆性致密砂岩裂缝扩展规律实验

岩石的脆性与致密油气储集层压裂改造效果密切相关,但致密岩石的脆性对裂缝扩展规律的影响仍不明确。基于真三轴压裂模拟实验系统,对鄂尔多斯盆地东部3种不同脆性致密砂岩开展了压裂模拟实验,分析了脆性、压裂液类型和层理对裂缝扩展规律的影响。研究表明,山1段致密砂岩脆性最强,长7段致密砂岩次之,盒8段致密砂岩脆性最弱;在层理不发育的条件下,相比于中等脆性的盒8段致密砂岩,强脆性的山1段致密砂岩采用滑溜水压裂形成的单条裂缝扩展更充分,液态CO₂压裂形成的分支裂缝数量更多;在层理发育的条件下,长7段致密砂岩采用滑溜水压裂和液态CO₂压裂形成的裂缝的形态均较复杂;相比于滑溜水压裂,液态CO₂压裂形成的裂缝宽度更小;液态CO₂压裂更适用于脆性较强、层理发育的长7段致密砂岩储集层压裂改造。     

Conductor selection and economic analysis of D.R. congo–guinea ±800 kV UHVDC transmission project

Africa is embracing new opportunities featured with industrialization, urbanization and regionalization. Based on co-development of ‘Electricity, Mining, Metallurgy, Industry and Trade’ and grids interconnection proposed by Global Energy Interconnection Development and Cooperation Organization (GEIDCO), the high-quality hydropower resource of the Congo River can be exploited in large scale under the wide-range interconnected framework of African Energy Interconnection (AEI), forging a new engine for Africa economy. The transmission distance of the Congo River hydropower reaches 6,000 km at its farthest end in North Africa, which brings forth challenges to economics of proposed projects. Under this novel continental energy interconnection scheme in Africa, economics of those projects have not yet been in detail studied. This paper has implemented China’s mature engineering experiences and analytical tools of UHVDC project planning into the AEI structure, through exploring the economic behavior of ultra-long distance UHVDC projects in the scope of conductor selection in the Congo River hydropower transmission for the first time, and has provided concerned parties with a technical and analytical results of their economics comparison. This paper has chosen the D.R. Congo - Guinea ±800 kV UHVDC project as a typical example. Its preliminary system planning is introduced and three types of conductor are selected for scheme comparison. Later in this paper, the transmission loss, total investment and equivalent annual cost of the project have been calculated and analyzed. In the final part, sensitivity analysis results of the annual cost to utilization hours, transmission loss, loss tariff and construction cost has been provided     

华北土石山区典型小流域土壤水文特征与模拟研究

土壤水文特征是研究区域水土资源合理配置的基础支撑要素,根据华北土石山区土壤的地貌分异规律,综合考虑地质、植被、土地利用等因素,采用野外调查取样法、环刀法等,研究了易县崇陵流域5种典型植被(油松、侧柏、银杏、刺槐、荆条)条件下的土壤物理性质、土壤水分特征曲线、土壤入渗过程等土壤水文特征。结果表明,同一植被条件下,土壤容重随土壤深度增加逐渐增大,同一深度条件下,荆条覆盖下的土壤容重最小,其他植被覆盖条件下的土壤容重差别不显著;同一植被条件下,随深度增加,饱和含水率逐渐减小,同一植被不同深度条件下的土壤水吸力随土壤含水率的增加逐渐减小;对土壤水分特征曲线进行拟合时,发现Gardner模型适用于油松和银杏,而张景略模型适用于侧柏、刺槐和荆条;土壤入渗过程的渗润阶段发生在土壤入渗开始的前10min内,渗漏阶段持续100~120min;侧柏最佳入渗模型为Kostiakov模型,而油松、银杏、刺槐及荆条最佳入渗模型为蒋定生模型。     

2D BASIN MODELLING IN THE EASTERN VARISCAN FOLD BELT (CZECH REPUBLIC): INFLUENCE OF THRUSTING ON PATTERNS OF THERMAL MATURATION

This study evaluates the geothermal history of Palaeozoic sedimentary rocks from the easternmost part of the Variscan external zone in the NE Czech Republic. The objective was to investigate the geothermal history of pre‐Variscan Palaeozoic carbonates in the study area, and to assess its relationship with that of the overlying Variscan flysch. In the study area, the Palaeozoic succession occurs at the surface or is overlain by Miocene sediments of the Carpathian Foredeep. Palaeozoic nappes and the main Variscan overthrust have been documented in the subsurface at the deep Pot?tát‐1borehole. Vitrinite reflectance measurements on 38 samples from the Pot?tát‐1 well and 19 samples from nearby surface outcrops and shallow boreholes were available. A 2D thermal model was created using PetroMod and the thermal maturity evolution was modelled by EASY%Ro. The thermal model was constructed based on interpretations of two NW‐SE seismic profiles (lines 5/83 and 5/84) oriented perpendicular to the main Variscan thrusts. The results were calibrated using measured vitrinite reflectance and were adjusted with 1D models from three shallow boreholes. At the Pot?tát‐1 borehole, modelled maximum palaeo‐temperatures of the Variscan flysch (Moravice Formation) ranged from 310°C at a depth of 7.3 km (the top of the preserved succession) to 395°C at the base of the succession, resulting in thermal maturities of >4%R_r. Peak maturation occurred prior to the end of Variscan thrusting. Modelling suggests that the basal heat flow for these thrust units reached a maximum value of 63 mW/m² at 325 Ma. In addition, the modelling suggests that the maturity of the Palaeozoic carbonates was controlled by the thickness of the overlying Variscan flysch nappes. Maximum palaeo‐temperatures for the Palaeozoic carbonates ranged from 265°C at the top of the interval (at a depth of 7.1 km) to 290°C at the base, resulting in a maturity of 3.8 to >4%R_r which is within the dry gas window. The study suggests that basal heat flows in the original (pre‐thrust) Early Carboniferous sedimentary basin were slightly higher than those in the post‐thrust location for the Variscan flysch nappes. This should be taken into account when evaluating the petroleum system in the South Moravian oil province (SW Czech Republic) where a complete sedimentary sequence has not been preserved.