Improving reservoir thickness prediction using seismic attributes and attributes fusion

Usage of any single attribute would introduce unacceptable uncertainty due to limited reservoir thickness and distribution, and strong lateral variations in lithological traps. In this paper, a wide range of prestack and post-stack seismic attributes is utilized to identify a range of properties of turbidity channel sandstone reservoir in Block L118 of J Oilfield, China. In order to better characterize the turbidity channel and lower the uncertainty, we applied multi-attribute fusion to weight a variety of seismic attributes in terms of their relevance to the identification of turbidity channel reservoir. Turbidity channel boundary is clearly present in the new attribute and the reservoir thickness prediction is improved. Additionally, fluid potential of reservoir was predicted using this fused attribute with a high value anomaly indicating high fluid potential. The multi-attribute fusion is a valid approach for the fine prediction of lithologic reservoirs, reducing the risks typically associated with exploration.     

长江口海平面上升对崇明三岛除涝安全的影响研究

对长江口海平面上升动态及其对沿海潮汐特性的影响进行了简析。结合长江口崇明三岛地区除涝安全面临海平面上升的影响和威胁,分别建立了基于海平面上升的上海市崇明三岛水系一维平原感潮河网水动力模型,深入开展了海平面上升对三岛地区除涝安全影响的模拟研究。结果显示,至2030年,长江口海平面上升10～16 cm,崇明三岛片区的面平均除涝最高水位、局部除涝最高水位均呈上升趋势,其中,崇明岛片受影响最大,对应水位将分别上升3～5 cm、4～6 cm;长兴岛片受影响次之,对应水位将分别上升3～4 cm、3～5 cm;横沙岛片受影响相对最小,对应水位均将上升1～2 cm;长江口海平面上升对崇明三岛的除涝安全影响在可控范围内。     

鄂尔多斯盆地富县探区三叠系延长组震积岩及其地质意义

通过对26口井岩心观察,结合区域构造背景,在鄂尔多斯盆地富县探区三叠系延长组中识别出典型的震积岩。该区震积岩代表性沉积构造有液化砂脉、液化卷曲变形、环状层理、负载构造、球枕构造、微断层、微裂缝、震裂岩与震碎角砾岩,其中液化砂脉和液化卷曲变形是地震引起的主要软沉积变形构造。震积岩垂向序列划分为两类:一种以脆性变形为主,自下向上依次为下伏未震层,扰动层,微断层、微裂缝及震裂岩层段,液化卷曲变形层段,震碎角砾岩层段,液化砂脉层段及上覆未震层;另一种以软沉积变形为主,自下至上依次为下伏未震层,环状层段,扰动层,球枕构造及负载构造层段,液化砂脉及液化卷曲变形层,枕状层及上覆未震层。富县探区延长组中的震积岩说明在该盆地晚三叠世存在一个强地震事件活跃期;震积岩中的微裂缝、微断层、震裂岩及液化砂脉可改善储集层物性,同时震碎角砾岩和网状砂脉也是良好的储集层。     

一种新的轮廓线三维地质表面重建方法

在三维地质建模中,由于地质剖面与医学CT有本质上的相似性,因此,轮廓线的三维表面重建技术有广泛的应用。目前,较为成熟的算法并没有考虑地质数据的特殊性,由于地质体形态复杂多变,地质剖面稀疏、数据来源多样等特点,将普适的算法应用到地质建模中,只是解决了重建曲面的合理性,并没有关注曲面的几何质量,导致曲面无法达到地质建模对于模型质量的要求。本文针对地质数据的特点,提出了一种新的轮廓线表面重构方法。在不改变轮廓线连接的合理性与正确性的情况下,通过生成过渡剖面轮廓线,克服传统方法生成曲面过于粗糙的缺点,以提高建模质量。在Creatar三维地质基础平台上,对多种情况的剖面数据实验结果表明,在数据稀疏的情况下达到了良好的建模效果。该方法的扩展模型满足了地质剖面轮廓线建模中复杂地质情况,以及交叉剖面数据的曲面重建,且算法复杂度低,实现简单,有较强的实用性。     

The clustering of barred galaxies in the local Universe

We study the clustering properties of barred galaxies using data from the Sloan Digital Sky Survey. We compute projected redshift-space two-point cross-correlation functions   w _p( r _p)  for a sample of nearly 1000 galaxies for which we have performed detailed structural decompositions using the methods described in Gadotti. The sample includes 286 barred galaxies. The clustering of barred and unbarred galaxies of similar stellar mass is indistinguishable over all the scales probed (∼20 kpc–30 Mpc). This result also holds even if the sample is restricted to bars with bluer   g − i   colours (and hence younger ages). Our result also does not change if we split our sample of barred galaxies according to bar-to-total luminosity ratio, bar boxyness, effective surface brightness, length or the shape of the surface density profile within the bar. There is a hint that red, elliptical bars are more strongly clustered than red and less elliptical bars, on scales  ≳1 Mpc  , although the statistical significance is not high. We conclude that there is no significant evidence that bars are a product of mergers or interactions. We tentatively interpret the stronger clustering of the more elliptical bars as evidence that they are located in older galaxies, which reside in more massive haloes.     

Alignment between galaxies and large-scale structure

Based on the Sloan Digital Sky Survey DR6 (SDSS) and the Millennium Simulation (MS), we investigate the alignment between galaxies and large-scale struc-ture. For this purpose, we develop two new statistical tools, namely the alignment cor-relation function and the cos(20)-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy cat-alog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous (L L*) galaxies out to projected separations of 60 h-1Mpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos(2θ)-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo (with size similar to that of the stellar galaxy). As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of ~ 25°. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for cen-tral galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference galaxy distribution to be flat-tened parallel to the orientations of red luminous galaxies with axis ratios of ~ 0.5 and ~ 0.75 for halo and central orientations, respectively. These ratios are almost independent of scale out to 60h-1Mpc.     

Ionization state of cosmic hydrogen by early stars and quasars

Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into ac-count. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2 z 6. Comparison with the classic Press-Schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 25 per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galax-ies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2 - 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～ 50 respectively. We find that the rel-ative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈ 2 and 2% at z ≈ 6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute esti-mates of the fraction of neutral hydrogen computed from theoretical models may not be important because of comparable uncertainties in the computation.     

海南岛三亚湾海滩研究*

海南岛三亚湾及其周边海滩可分为两种主要类型:一类是岩礁海岸海滩,发育于基岩和珊瑚礁岛波影区或珊瑚礁平台后侧,多为背叠式砂砾滩,滩窄、坡陡,具有数道陡坎,在岛礁背风侧常发育不同阶段的连岛坝,如白排人工岛西南端海滩、鹿回头湾大洲后侧及对岸的海滩、鹿回头湾和小东海海滩;另一类是沙坝海岸海滩,发育于向外海敞开的大沙坝的向海侧,海湾内砂质沉积物丰富,形成滩脊式或背叠式砂质滩,滩面宽坦,物质较细,如三亚湾和大东海海滩。因湾口朝向与湾内岛礁分布发育情况不同,湾内受常浪和台风强浪作用的强度与频率不同,加之现代泥沙补给情况的差异,这一类海滩的形态结构亦不尽相同。如三亚湾西侧近岬角处,波能辐聚,动力强,侵蚀作用突出,滩面呈近直线形倾斜,并形成两道陡坎;三亚湾中部,受岛礁保护,滩面宽阔,波浪消能空间充足,物质丰富,发育滩脊型海滩,滩面呈上凸形,基本稳定;三亚湾东侧,虽有岛礁掩蔽,但由于人为修建的绿地草坪带和水泥碎砖石小径等,建设高度过低, 束狭了激浪带的自由作用宽度,减小了波浪消能范围,破坏了海滩的整体结构,同时阻断了沙坝向海滩的供沙, 使滩面坡度加大,物质粗化,局部与小径相接处形成侵蚀陡坎、椰树等倾斜,呈侵蚀状态。     

新一代天气雷达（ＣＢ）发射机的检测与维修

利用2006年和2007年太原地区的闪电定位资料,分析了太原地区地闪的日变化、月变化、闪电强度、闪电密度等特征结果表明：太原地区的正地闪比例明显低于我国北方地区的其它城市;总地闪和负地闪的日变化呈典型的双峰变化正闪的双峰特征不明显;太原市辖区北部和阳曲县是闪电频发的中心地带,闪电空间分布中心与冰雹发生源地和影响区对应一致;闪电多发区与地形、气候背景以及城市热岛效应有很大关系。     

基于经验模态分解的西安市空气质量预报订正方法

为提高城市空气质量预报的准确率,研制了针对数值预报模式CAPPS2的订正方法,对2001—2007年西安市逐日PM10、SO_2、NO_2浓度均值和相应的降水、风速作经验模态分解(EMD)分析,用最大熵谱方法检验各本征模态函数(IMF)周期,计算其方差贡献率,制定订正方法并进行数值试验。结果表明:PM10浓度波动以周尺度为主,有明显周末效应,与主要清除过程匹配较好;SO_2、NO_2浓度波动与主要清除过程不同步;基于周末效应的订正规则对PM10、SO_2订正效果较理想,对NO_2订正效果不确定。