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131.
长江中下游地区页岩气调查井工程,采用绳索取心钻进工艺,钻遇地层多为泥质含量高的水敏性泥岩、软硬互层较为频繁的致密性地层。钻进过程中,金刚石钻头经常出现钻头泥包现象,在软硬夹层中PDC钻头崩齿导致钻头机械钻速和寿命受到严重影响。主要从钻头结构及钻井液性能方面系统分析了金刚石钻头泥包及PDC钻头崩齿的原因,分析认为,现场钻头应用过程中产生的上述问题与钻头唇面结构设计、钻头水路设计、钻头材料与表面状态、钻进规程参数及钻井液性能有着密切关系。通过对钻进工艺、地层岩性分析研究,对原有钻头进行了结构形式优化和改进设计,对钻进规程参数也进行了优化,现场应用结果表明:钻速明显提升,大大提高了泥岩段及夹层段的钻进效率。 相似文献
132.
本文用数值计算的方法解非线性耦合薛定谔方程 ,研究了在非偏振保持光纤中随机双折射变化对孤子自俘获传输现象的影响。研究结果表明 :相对于具有保偏特性的强双折射光纤 ,非偏振保持光纤中随机双折射所致的 2个模式间频繁的能量交换 ,减缓了 2脉冲的走离 ,有利于束缚态的形成 ;入射偏振角 θ对孤子的自俘获传输影响非常小 ,这就使光孤子耦合进光纤时不须鉴别光纤的快、慢轴。 相似文献
133.
The evolution and decay of El Niño 1997–8 was observed in coastal waters off Oregon in a sequence of cruises along 44.6°N from the coast to more than 150 km offshore. Hydrographic observations were made during eleven cruises between July 1997 and April 1999 at stations on the Newport Hydrographic Line, which had been occupied regularly from 1961 to 1971. The data from the earlier decade provide a basis for defining ‘normal’ conditions and allow comparisons with the recent El Niño in terms of T, S, spiciness and geostrophic velocity. Independent of El Niño, the ocean in July 1997 was already anomalously warm offshore of 50 km and above 100 m. By September 1997 there were unambiguous indications of El Niño: isotherms and isohalines sloped down toward the coast indicating poleward flow over shelf and slope, and anomalously spicy water was present at the shelf-break. In November 1997 and February 1998 shelf-break waters were even warmer, and there was strong poleward flow inshore of 100 km, extending to depths greater than 200 m. The April 1998 section closely resembled that of April 1983 (another El Niño year) but by June 1998 the anomalies were mostly gone. November 1998 was near normal and the sections from subsequent cruises resemble the mean sections from 1961–1971.Four cruises between November 1997 and November 1998 included sampling at several latitudes between 38° and 45°N. As expected, these sections show significant alongshore gradients, but also a surprising degree of homogeneity in the anomalous features associated with El Niño (in the temperature, salinity, spiciness and geostrophic velocity fields). The anomalous signature of El Niño was stronger at its winter peak in 1998 than in 1983, but the signature in the temperature and spiciness fields, and in coastal sea level, did not persist as long as in 1983. By April 1999, the coastal ocean from 38°N to 45°N was significantly colder than it had been in April 1984. 相似文献
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Early studies suggested that the Aleutian–Icelandic low seesaw(AIS) features multidecadal variation. In this study, the multidecadal modulation of the AIS and associated surface climate by the Atlantic Multidecadal Oscillation(AMO) during late winter(February–March) is explored with observational data. It is shown that, in the cold phase of the AMO(AMO|-),a clear AIS is established, while this is not the case in the warm phase of the AMO(AMO|+). The surface climate over Eurasia is significantly influenced by the AMO's modulation of the Aleutian low(AL). For example, the weak AL in AMO|-displays warmer surface temperatures over the entire Far East and along the Russian Arctic coast and into Northern Europe,but only over the Russian Far East in AMO|+. Similarly, precipitation decreases over central Europe with the weak AL in AMO|-, but decreases over northern Europe and increases over southern Europe in AMO|+.The mechanism underlying the influence of AMO|-on the AIS can be described as follows: AMO|-weakens the upward component of the Eliassen–Palm flux along the polar waveguide by reducing atmospheric blocking occurrence over the Euro–Atlantic sector, and hence drives an enhanced stratospheric polar vortex. With the intensified polar night jet, the wave trains originating over the central North Pacific can propagate horizontally through North America and extend into the North Atlantic, favoring an eastward-extended Pacific–North America–Atlantic pattern, and resulting in a significant AIS at the surface during late winter. 相似文献
138.
Donghai Zhang Xiang Chen Zhoutao Zheng Xiafei Zhou Tao Jiang 《International Journal of Digital Earth》2016,9(10):1021-1034
The false topographic perception phenomenon (FTPP) refers to the visual misperception in remote-sensing images that certain types of terrains are visually interpreted as other types in rugged lands, for example, valleys as ridges and troughs as peaks. For this reason, the FTPP can influence the visualization and interpretation of images to a great extent. To scrutinize this problem, the paper firstly reviews and tests the existing FTPP-correction techniques and identifies the inverse slope-matching technique as an effective approach to visually enhance remote-sensing images and retain the colour information. The paper then proposes an improved FTPP-correction procedure that incorporates other image-processing techniques (e.g. linear stretch, histogram matching, and flat-area replacement) to enhance the performance of this technique. A further evaluation of the proposed technique is conducted by applying the technique to various study areas and using different types of remote-sensing images. The result indicates the method is relatively robust and will be a significant extension to geovisual analytics in digital earth research. 相似文献
139.
新密煤田瓦斯动力现象分析 总被引:2,自引:0,他引:2
为研究新密煤田发生低瓦斯含量、低瓦斯压力瓦斯动力现象的原因,解决低指标瓦斯动力现象给生产带来的危害,运用区域构造演化理论分析了新密煤田自印支期至今的构造演化,统计分析了区域内38次瓦斯动力现象和167个采样地点的煤岩坚固性系数f值,结合《防治煤与瓦斯突出细则》及常规实践经验,与新密煤田瓦斯动力现象中煤层瓦斯含量、瓦斯压力做了对比。结果表明,区域内的瓦斯动力现象表现为低瓦斯含量、低瓦斯压力,f值多在0.3以下;基于综合假说机理的研究表明,构造煤普遍发育、煤岩坚固性系数f值小是该现象的深层原因。 相似文献
140.
泥火山形成于特定的水文地质及构造环境,其喷发活动是内部大量气体聚集引起异常高压的一种释放,可以将大量地下信息携带到地表,被称为"天赐钻井"。新疆乌苏艾其沟泥火山实时观测始于2011年8月,自观测以来,在其周围200m范围内,共发生了4次6级以上地震,分别是2011年11月1日新疆尼勒克M_S6.0、2012年6月30日新疆新源M_S6.6、2016年12月8日新疆呼图壁县M_S6.2及2017年8月9日精河M_S6.6地震。在4次地震前后,艾其沟泥火山喷发活动均出现了"背景值—上升—转折—下降—背景值"的宏观异常变化现象,地震则发生在泥火山喷发活动由强到弱的过程中,尤其是在2017年精河M_S6.6地震时,乌苏艾其沟泥火山的喷发活动异常变化现象为新疆地震局做出震情形势判定提供了一部分依据,具有一定的减灾实效。 相似文献