Approach to calculating spatial similarity degrees of the same river basin networks on multi-scale maps

Obtaining spatial similarity degrees among the same objects on multi-scale maps is of importance in map generalization. This paper firstly defines the concepts of ‘map scale change’ and ‘spatial similarity degree’; then it proposes a model for calculating the spatial similarity degree between a river basin network at one scale and its generalized version at another scale. After this, it validates the new model and gets 16 points in the model validation process. The x-coordinate and y-coordinate of each point are map scale change and spatial similarity degree, respectively. Last, a formula for calculating spatial similarity degree taking map scale change as the only variable is obtained by the curve fitting method. The formula along with the model can be used to automate the algorithms for simplifying river basin networks.     

基于小波分析的抚松县降水量变化对矿泉水资源量的响应研究

大气降水是抚松县矿泉水资源的重要补给来源,探究其变化规律及极值概率对泉流量是否能够得到持续补给具有重要意义。为此,首先利用1960~2013年的降水资料和1981~2008年部分泉流量观测数据,对抚松县降水量的年内分配、年际变化和不同年代降水量均值变化进行降水特征分析;之后,运用皮尔逊Ⅲ型模型分析最大年降水量的概率分布;接着,利用1981年7月~2008年11月期间降水量和部分泉的泉流量监测数据,采用连续小波分析法对二者周期进行分析;最后,运用交叉小波变换法对同一时段内降水量和泉流量多时间尺度变化的相关性进行分析。结果表明:1960~2013年的54间,研究区内年降水量呈现周期性变化,变差系数为1.017×10-17,降水稳定,未发生异常变化。降水量和泉流量均存在约11个月的主震荡周期,二者属于同相位(即泉流量对降水量的变化产生即刻反应),降水量作为本区矿泉水补给的重要影响因素,可为矿泉水资源得到有效补给提供保证。     

Seismic attenuation estimation using a complete ensemble empirical mode decomposition-based method

The frequency attenuation gradient method can provide important information for hydrocarbon detection. In this paper, a method using Complete Ensemble Empirical Mode Decomposition (CEEMD), Hilbert transform and the least-squares curve-fitting is proposed for seismic attenuation estimation as an effective frequency attenuation gradient estimation approach. We first use CEEMD to obtain the different Intrinsic Mode Functions (IMFs), which have a narrow band and can enhance the physical meaning of instantaneous attributes trace by trace. The time-frequency spectrum, which is computed using a Hilbert transform of each IMF, is represented as a spectrum with a single-peak that has narrow side lobes, which is conducive to frequency attenuation gradient estimation. Second, for each time sample, the frequency-amplitude spectrum of each IMF trace is extracted from the time-frequency spectrum to conduct the attenuation gradient computation. Then, the logarithm operation is performed for each IMF trace. Due to the very narrow bands of some IMFs in some seismic traces, a variable frequency window is adopted along the IMF trace according to the local data characteristics. Finally, the attenuation gradient for each IMF in a seismic trace can be computed using least-squares fitting. A different IMF reflects a seismic trace with a different spatiotemporal scale and can highlight different geologic and stratigraphic information. The correlation weighted average operation is used to highlight some useful details in seismic trace and obtains the attenuation gradient for each seismic trace. Field data examples demonstrate our method and its effectiveness. The proposed method can stably estimate the frequency attenuation gradient.     

Application of multi-seismic attributes analysis in the study of distributary channels

During the exploration of stratigraphic reservoirs, the key to locating these reservoirs is to identify the sandstone distribution. Seismic data can be used to recognize large-scale distributary-channel sedimentary bodies; however, depiction of sedimentary bodies in small distributary channels using traditional interpretation data from seismic profiles is extremely difficult. In the Upper Cretaceous first sandstone bed of the third member of the Nenjiang Formation (called the Nen 3 member for simplicity) in the XB area of the southern Songliao basin, distributary channels are the main sedimentary facies. The distributary channels migrate frequently; therefore, it is difficult to precisely depict the morphology of the channel and the distribution of sandstone. In this study, we investigated the deposition of distributary channels using equal-scale formation plane seismic attributes such as post-stack amplitude, instantaneous amplitude and seismic waveform classification, analyzed well logging data from target formations, and mapped the distribution of distributary channels. This study shows that seismic sedimentological study and stacking multiple attribute analysis can identify the distribution of distributary channels precisely and effectively. The attributes of equal-scale strata slices are evidently superior to those of time and horizon slices; Attribute extraction and selection of equal-scale formation slices is an essential step. The comprehensive selection of seismic attributes that show a good correlation to a single-well can be used to clearly depict channel bodies. The overlap of the 40-Hz single-frequency energy and the RMS amplitude depicts the sedimentary characteristics and shapes of sandstone bodies in main channels as well as small-scale distributary channels more clearly than a single attribute. These attributes show that the first sandstone bed of the Nen 3 member was from distributary channels with complex shapes. The distributary channels cut across each other vertically and laterally. It indicates that, during the deposition of the Nen 3 member in XB area, the direction of the main channel is from north to south, and the provenance could be from north and east. The method of this paper may provide some helpful suggestions to the geologist using seismic attributes to undertake research on sedimentary environment at other places in the world.     

岬湾海滩剖面中长期变化特征及其控制因素——以青岛石老人海滩为例

了解海滩剖面变化可以更好地理解海滩动态过程。利用2007年5月~2014年12月近8 a青岛石老人海滩剖面的实测资料,计算剖面各段单宽体积变化量及后滨宽度,结合交叉小波和小波相干分析方法,探讨海滩剖面中长期淤蚀变化特征及其控制因素。结果表明,近8 a来海滩剖面表现为侵蚀状态,不同岸段侵蚀程度不同。剖面1岸段侵蚀明显,剖面2和剖面3岸段轻微侵蚀。剖面的变化过程可划分为平稳期、剧变期和微调期3个时期。各时期剖面的季节性变化较复杂,平稳期具冬蚀夏淤的交替变化特征,整体淤蚀量较小;剧变期剖面呈阶段性蚀退,变化幅度相对较大,微调期剖面可能仍处于剧变期的恢复阶段,季节性变化不明显。剧变期和微调期的小波交叉谱和相干谱分析显示,波浪和前滨单宽体积相干性较好,尤其当大于2 m的波高达到10%以上,海滩地形可以和波高变化产生同周期的变化。因此波高变化基本控制了剖面的季节变化。而海滩长周期变化主要受控于风暴潮作用及其漫长的恢复期,沿岸输沙和海平面变化则一定程度上导致了剖面长期侵蚀格局的形成。     

频谱分解技术在泥页岩储层含气性预测中的应用——以柴达木盆地鱼卡凹陷为例

针对柴达木盆地北缘鱼卡凹陷中侏罗统大煤沟组泥页岩,利用地震频谱曲线在不同流体介质储层中的形态、斜率、主频与中心频率的差值等属性参数特征,识别陆相泥页岩层系的地震频谱属性特征,预测含气性。研究结果表明,中侏罗统大煤沟组上部能量系数较低,平均为0.6719,下部能量系数较高,平均为0.7521,结合现场含气量和全烃特征认为,可以以能量系数0.7为界线,作为识别下部和上部含气性的标志,下部明显比上部含气性好。平面上进一步圈定了2个有利目标区,得到柴页1井勘探验证。因此,频谱分解技术可应用于中国陆相页岩气的勘查开发。     

应用两次展开法求解系泊柱体慢漂运动方程

在深海中系泊的海洋平台,如Spar平台,水下部分为带有系泊的圆柱结构,其水平方向运动响应往往具有较低的自振频率,容易在低频波浪力(源于非线性的差频效应)作用下发生共振响应,使结构发生大幅水平慢漂。当浮体的瞬时位置大幅偏离初始位置时,基于初始平衡位置的摄动展开法会存在较大误差。针对这一问题,采用两次展开方法,对大幅慢漂运动开展时域模拟研究。对双色波作用下自由漂浮圆柱的大幅运动响应问题进行数值分析,并与采用基于初始平衡位置的摄动展开法的计算结果进行了对比。结果表明,采用新的两次展开法可以计算出波浪遭遇频率的变化和波浪漂移阻尼,而这无法从基于初始平衡位置的常规摄动展开法中得到,体现了两次展开法在分析大幅慢漂问题上的优势。     

内蒙古翁公敖包航磁异常的推断与解释

文章对内蒙古四子王旗—土默特右旗中北部近年发现的翁公敖包航磁异常进行推断与解释,在对找矿有望的航磁异常进行筛选后,对翁公敖包航磁异常进行了野外地质-地球物理查证,确定异常为铁矿所致;采用向上延拓、垂向导数、斜导数及小波变换等方法对航磁异常进行数据转换处理,以获取铁矿体的横向及纵向分布信息,取得了较好的效果。     

基于小波分析与Mann-Kendall法的岩溶大泉动态研究

研究地下水动态是认识地下水资源的有效手段。根据1956－2013年济南岩溶泉域大气降水及地下水水位动态监测资料,采用小波分析法、Mann-Kendall趋势检验、突变检验法研究了58个水文年泉水位对大气降水的响应,可以看出:（1）大气降水和泉水位呈现出多尺度的变化特征,长时间尺度上两者的变化周期基本相同,变化周期为16年和12年,说明大气降水对泉水位有直接影响;（2）在1956—2013年,济南泉域地下水水位具有0.65 m·（10a）-1的年际显著下降趋势,但降水具有12.65 mm·（10a）-1的不显著上升趋势,说明在人为因素影响下泉水动态的影响因素的权重发生了变化;（3）大气降水在1999年发生突变,1999年之后年降水为增加趋势;而地下水水位突变年份为1967年,1967年以后水位持续降低,2004年以后水位快速上升,泉水位未来趋势应与降水保持一致,呈上升趋势,说明大气降水并非泉水动态的唯一影响因素;（4）通过建立不同时段的多元回归模型,表明近58年来地下水水位的主要影响因素由大气降水到人工开采之间的转换,同时验证了小波分析和Mann-Kendall法研究地下水动态的适宜性和可靠性,也为济南市的保泉提供了参考依据。      

磁法三维建模在龙王沟磁铁矿勘探中的应用

以龙王沟磁铁矿高精度磁测数据为基础,采用小波多尺度分解方法,对化极后的磁法数据进行多尺度分解,通过功率谱法计算小波多尺度分解后的各阶细节异常的场源深度。结合地形、地质及钻孔资料,采用2.5D人机交互反演对磁测剖面上的磁铁矿体进行拟合,利用Golden Software公司开发的Voxler软件,在虚拟三维环境下实现二维小波多尺度分解数据的可视化,建立三维地质体模型,直观的预测磁铁矿体的空间范围和分布形态,实现地质、物探和地上、地下信息一体化集成展示,进行专业分析评价和辅助决策,可以有效的提高地质找矿效果。