Controls on reservoir heterogeneity of tight sand oil reservoirs in Upper Triassic Yanchang Formation in Longdong Area,southwest Ordos Basin,China: Implications for reservoir quality prediction and oil accumulation

Compared to conventional reservoirs, pore structure and diagenetic alterations of unconventional tight sand oil reservoirs are highly heterogeneous. The Upper Triassic Yanchang Formation is a major tight-oil-bearing formation in the Ordos Basin, providing an opportunity to study the factors that control reservoir heterogeneity and the heterogeneity of oil accumulation in tight oil sandstones.The Chang 8 tight oil sandstone in the study area is comprised of fine-to medium-grained, moderately to well-sorted lithic arkose and feldspathic litharenite. The reservoir quality is extremely heterogeneous due to large heterogeneities in the depositional facies, pore structures and diagenetic alterations. Small throat size is believed to be responsible for the ultra-low permeability in tight oil reservoirs. Most reservoirs with good reservoir quality, larger pore-throat size, lower pore-throat radius ratio and well pore connectivity were deposited in high-energy environments, such as distributary channels and mouth bars. For a given depositional facies, reservoir quality varies with the bedding structures. Massive- or parallel-bedded sandstones are more favorable for the development of porosity and permeability sweet zones for oil charging and accumulation than cross-bedded sandstones.Authigenic chlorite rim cementation and dissolution of unstable detrital grains are two major diagenetic processes that preserve porosity and permeability sweet zones in oil-bearing intervals. Nevertheless, chlorite rims cannot effectively preserve porosity-permeability when the chlorite content is greater than a threshold value of 7%, and compaction played a minor role in porosity destruction in the situation. Intensive cementation of pore-lining chlorites significantly reduces reservoir permeability by obstructing the pore-throats and reducing their connectivity. Stratigraphically, sandstones within 1 m from adjacent sandstone-mudstone contacts are usually tightly cemented (carbonate cement > 10%) with low porosity and permeability (lower than 10% and 0.1 mD, respectively). The carbonate cement most likely originates from external sources, probably derived from the surrounding mudstone. Most late carbonate cements filled the previously dissolved intra-feldspar pores and the residual intergranular pores, and finally formed the tight reservoirs.The petrophysical properties significantly control the fluid flow capability and the oil charging/accumulation capability of the Chang 8 tight sandstones. Oil layers usually have oil saturation greater than 40%. A pore-throat radius of less than 0.4 μm is not effective for producible oil to flow, and the cut off of porosity and permeability for the net pay are 7% and 0.1 mD, respectively.     

Occurrence and Chemical Compositions of Amphiboles in Altered Dioritic Rocks of Laiwu Skarn‐Type Iron Deposit in West Shandong Area,China

The Laiwu Fe deposit is the largest skarn‐type deposit in West Shandong in China, with an estimated reserve of 290 Mt of iron ore. Here, we investigate the occurrence and chemical composition of amphiboles in altered dioritic rocks of this deposit. Three generations of amphibole group minerals were identified in these rocks. The first type (Type 1) is a hornblende with a generally euhedral crystal shape, 150–500 μm in size, and dominantly occurs in the host monzonite. The second type (Type 2) of hornblende occurs as fine grains (<100 μm) or concentric rims, less than 50 μm in thickness, around the Type 1 hornblende. The third type (Type 3) of amphibole is anhedral actinolite occurring along the boundary or the cracks of the Type 1 or 2 hornblende grains. The Type 1 hornblende has higher FeO (12.5–15.6 wt.%) and lower MgO contents (11.2–14.6 wt.%) than the Type 2 hornblende, which has an FeO content ranging from 8.8 to 10.5 wt.% and MgO content ranging from 14.2 to 17.1 wt.%. The Type 3 actinolite shows the lowest FeO (4.6–6.4 wt.%) and highest MgO (19.8–21.2 wt.%) contents. We infer that the Type 2 hornblende formed from Fe‐rich hydrothermal fluids released during rapid upwelling of the crystallizing magma. The fluids were relatively reduced and enriched in Fe. The Type 3 actinolite formed by coupled dissolution and reprecipitation, and its formation is one of the features denoting Fe‐enrichment events. Our study of these types of amphibole provides insights into the ore formation process.     

柳河盆地中生代充填特征与盆地演化

柳河盆地中生代地层发育有中侏罗统侯家屯组,下白垩统果松组、鹰嘴砬子组、林子头组、下桦皮甸子组和亨通山组。主要岩石类型为碎屑岩、火山碎屑沉积岩、火山碎屑岩和熔岩,沉积相为扇三角洲-湖泊相。根据岩性变化和岩相组合,将下白垩统划分为13个三级层序和8种充填类型。根据盆地构造和层序特征,划分为5个构造发育阶段,分别是中侏罗世初始凹陷阶段、晚侏罗世抬升剥蚀阶段和早白垩世的3个火山喷发-沉降阶段。柳河盆地是一个受走滑张扭-走滑压扭机制控制的走滑伸展盆地。     

基于遥感的大兴安岭小扬气镇用地类型变化及生态环境状况评价

大兴安岭小扬气镇位于大兴安岭南部,属大小兴安岭森林生态功能区,森林覆盖率高,湿地资源丰富,曾是木材生产基地。为掌握小扬气镇用地类型现状及其变化,开展生态状况评价,利用多源卫星遥感数据,通过多尺度图像分割、决策树及目视解译等方法分别对该区1985年、1998年、2008年和2018年土地利用类型进行提取,计算生态环境状况指数(I_E),评价生态环境状况。结果表明: 小扬气镇土地利用类型以林地、沼泽、水域为主,三者占研究区总面积的97%以上; 沼泽草地主要由阔叶林转化而来,耕地主要由阔叶林、沼泽草地转化而来,草地主要转化为阔叶林、沼泽草地,阔叶林与沼泽草地之间的相互转化最为剧烈; 新增工矿仓储用地主要占用了原有阔叶林土地,新增住宅用地主要占用了原有的沼泽草地、阔叶林、森林沼泽等。总体来看,区内生态环境状况良好,在维护生态安全、促进当地绿色经济发展中起到了重要作用。     

两类El Niňo事件次年夏季长江-黄河流域降水低频特征及低频水汽输送途径差异

利用1961年1月—2014年12月Hadley气候预测研究中心的全球海表温度(SST)资料,NECP/NCAR逐日风场、比湿等再分析资料,国家气象信息中心提供的中国753站逐日降水、160站逐月降水资料,对比分析了东部(EP)型和中部(CP)型两类El Niňo事件次年夏季长江-黄河流域降水(简记为EP型和CP型降水)低频特征,以及与之相关的低频水汽输送差异。结果表明,1)平均而言,EP型降水主要有10～20 d(最显著)以及20～30 d(次显著)低频周期;CP型降水主要有10～20 d的低频显著周期。与之相关的纬、经向水汽通量最显著低频周期也为10～20 d。2)影响EP、CP型低频降水共同的低频水汽环流系统主要有:菲律宾群岛附近的异常反气旋式水汽环流和渤海湾附近(日本东南侧)的异常气旋式(反气旋式)水汽环流。另外,影响EP(CP)型低频降水的还有来自巴尔喀什湖东北部异常气旋式水汽环流(孟加拉湾、苏门答腊岛以西的异常气旋式水汽环流对和贝加尔湖西、东两侧的异常气旋式、反气旋式环流)。3)EP型降水暖湿水汽主要源自南海,冷湿水汽主要源自西北太平洋,冷空气来自巴尔喀什湖东北部和贝加尔湖西北侧。CP型降水暖湿水汽少量来自阿拉伯海和印度洋,大量来自热带西太平洋,冷空气主要来自贝加尔湖西北侧。     

Experimental study on the effect of bottomless structure in front of a bottom outlet on a sediment flushing cone

One of the main problems in reservoirs is sedimentation which reduces the operating life of dams if a proper plan and analysis method are not in place.The techniques to manage sediment in reservoirs include several sustainable management techniques that route sediment through or around the reservoir.One of the main economical methods in arid and semi-arid regions is pressurized flushing using moderate drawdown of the water level of the reservoir to evacuate sediment deposited behind dams.In the current study,the effect of a new structure called a dendritic bottomless extended(DBE)outlet structure at three angles of 30°,45°,and 60°
on pressurized flushing efficiency was investigated.Consequently,45 experiments were designed for three discharge rates (Qo),three sediment levels(Hs),four types of structure,and a no-structure condition(reference test).The results indicated that the DBE structure with a 30°angle between the branches,a sedimentary dimensionless index of Hs/Do=4.59,and a flow dimensionless index of Qo=/√gD05=1:43(where g is the acceleration of gravity and Do is the diameter of the bottom outlet)lead to 10-fold increase in the sediment flushing cone dimensions and sediment removal efficiency compared to the results of the reference test.Finally,according to a statistical analysis of the results,a dimensionless equation for calculating the sediment flushing cone dimensions was developed for the tested sediment characteristics.     

从闪锌矿标型特征论台江龙井街铅锌矿成因

通过对闪锌矿的矿物共生组合,成分、形态及物理性质标型特征的研究,讨论了台江龙井街铅锌矿的成矿物质来源、成矿温度及成因类型。     

不同草地类型净初级生产力(NPP)模拟及其敏感性分析

气候变化问题作为人类社会可持续发展面临的重大挑战,受到国际社会越来越强烈的关注.全球气候变化深刻影响着草地生态系统,定量评估区域和不同类型草地生态系统的生产力,研究其对气候变化的敏感性可以为草地生态系统适应未来气候变化提供基础数据和理论依据.草原综合顺序分类系统(CSCS)将天然草原分为42类(其中中国包含41类),并...     

鄂尔多斯盆地南部旬邑-宜君地区中生界储层特征

对鄂尔多斯盆地南部旬邑 -宜君地区中生界主要储集层——直罗组、延安组、延长组储层特征从沉积相、砂体纵向展布、岩性和物性等几方面进行了简要论述。通过研究指出本区储层具有低孔、低渗的特点。在纵向上以直罗组储层相对最好 ,延安组次之 ,之后才是三叠系延长组。储集层普遍具有岩性细、成岩后生变化强烈的特点。由于储层低孔、低渗 ,因此 ,油层的压裂改造措施必不可少     

An introduction to the classification of the physiognomic landscape types: methodology and results of testing in the area of Kazimierz Landscape Park (Poland)

The publication of the European Landscape Convention (2000) had a stimulating effect on the development of both new systems of landscape classification and new methods of their evaluation and mapping. As an example, a new classification of physiognomic landscape types was developed in Poland in 2014. The objectives of the paper are to (1) popularize, on the international scale, the classification of physiognomic landscape types in a new, improved version, (2) present the original method of physiognomic landscape types mapping with the use of the system of basic landscape units, and (3) present the results of testing of the method in the area of the Kazimierz Landscape Park, Poland. In the area of the Kazimierz Landscape Park, 491 basic landscape units were delimited, within which, on the basis of the leading traits of land relief and cover forms, the physiognomic landscape types were identified. Maps of this type can be important tools in implementing the recommendations of the European Landscape Convention. The total number of physiognomic landscape types identified within a specific area can be one of the key indicators of landscape diversity.