Elastic impedance based facies classification using support vector machine and deep learning

Machine learning methods including support-vector-machine and deep learning are applied to facies classification problems using elastic impedances acquired from a Paleocene oil discovery in the UK Central North Sea. Both of the supervised learning approaches showed similar accuracy when predicting facies after the optimization of hyperparameters derived from well data. However, the results obtained by deep learning provided better correlation with available wells and more precise decision boundaries in cross-plot space when compared to the support-vector-machine approach. Results from the support-vector-machine and deep learning classifications are compared against a simplified linear projection based classification and a Bayes-based approach. Differences between the various facies classification methods are connected by not only their methodological differences but also human interactions connected to the selection of machine learning parameters. Despite the observed differences, machine learning applications, such as deep learning, have the potential to become standardized in the industry for the interpretation of amplitude versus offset cross-plot problems, thus providing an automated facies classification approach.     

WTO《补贴与反补贴措施协定》附件一(K)款二项的解释与适用——以加拿大飞机补贴案为例

WTO《补贴与反补贴措施协定》附件一(K)款二项是一个较为复杂和重要的条款,涉及的内容较多,如“官方出口信贷的国际承诺”、“后续承诺”、“出口信贷做法”、“符合”等措辞的解释与适用问题。在巴西诉加拿大影响民用飞机出口措施案中,专家组及上诉机构的报告对于澄清上述问题起了重要的作用。     

Application of spectral decomposition and neural networks to characterise deep turbidite systems in the outer fold and thrust belt of the Niger Delta

We have applied a wavelet‐based spectral decomposition scheme and a multi‐layered feed‐forward neural network to interpret turbidite depositional systems from three‐dimensional reflection seismic data and well logs for a prospective hydrocarbon zone in the outer fold and thrust belt of the Niger Delta. The goal was to overcome difficulties in interpreting depositional systems from deep sections of the Field, occasioned by loss of seismic resolution with depth and the sparse distribution of wells. The decomposition scheme allowed us to delineate multiple depositional systems not apparent on the conventional seismic amplitude display. These systems include linear channel systems with terminal splay lobes, a sinuous channel system and its abandoned meander loops, and sediment wave features in overbank areas. Delineated channel morphologies and transport directions varied both laterally and vertically and were possibly dependent upon the disposition of the pre‐thrusting paleo‐seafloor. Terminal splay lobes are fragmented and coincident with the locations of topographic lows, which are possibly related to the initial configurations of the oceanic basement below. Predicted porosity and resistivity distributions have morphologies that correlate well with the mapping provided by the spectral decomposition scheme. The property distributions indicate that reservoir prone systems in the Field and possibly within the outer fold and thrust belt are composed primarily of channel systems, both linear and sinuous, and their associated splay lobes. The channel systems appear vertically stacked, and this situation possibly increases the potential success rate for exploration wells in the region. Beyond channel limits, redistributive bottom currents varying rapidly in speed and direction apparently encouraged the dispersal of sand‐rich sediments to form sediment waves. Despite the limited well control, the methodology significantly aided our interpretation. It proved effective at revealing the distribution of reservoir prone facies within the Field and provided insight into the dominant factors that controlled deposition within the Field.     

1718年通渭M7.5地震滑坡特征分析——黄土高原历史强震触发滑坡数据库的应用

利用新技术、新方法,研究历史强震的发震构造及震害,是修订历史强震震源参数的重要内容.本文以1718年通渭M 7.5地震滑坡为研究对象,采用地质学“将今论古”原理,基于历史文献分析、遥感解译、野外验证等方法获得通渭地震滑坡数据库.研究发现,(1)总解译滑坡数量5019处,总面积635 km^2,滑坡密集沿通渭断裂分布,与X度等震线吻合,但范围均向西、向北各扩展约20 km;(2)与2008年汶川M8地震滑坡相比,面积<10^3 m^2的滑坡大量缺失,面积10^3~10^4 m^2的滑坡部分缺失,面积>10^4 m^2的滑坡数量相当;(3)尽管通渭地震滑坡数据库并不完整,但是能够反映极震区中大型滑坡的总体特征,可据此确定极震区范围;(4)通渭地震极震区至少有27处以“泄山”等记录地震滑坡的地名,这些受滑坡影响的居民点集中在通渭断裂两侧,占比超过50%,是致7万人死亡的重要致灾因素.研究认为,在黄土高原地区,确认密集的中大型滑坡体可能由单次历史强震触发,且排除其他远场强震影响之后,可以利用现今多时相的高分辨率卫星影像解译获得“相对完整”的历史地震滑坡数据库,为历史强震震源参数的修订提供基础资料.     

A new contribution to the geology of the Egyptian Red Sea shelf using geophysical data

The study examines the Egyptian Red Sea shelf and throws more light on the structural set-up and tectonics controlling the general framework of the area and nature of the crust. Herein, an integrated study using gravity and magnetic data with the available seismic reflection lines and wells information was carried out along the offshore area. The Bouguer and reduced-to-pole aeromagnetic maps were processed and reinterpreted in terms of rifting and plate tectonics. The qualitative interpretation shows that the offshore area is characterized by positive gravity everywhere that extremely increases towards the centre of the graben, supporting the presence of an intrusive zone below the axial/main trough. The gravity data were confirmed by the presence of high magnetic amplitudes, magnetic linearity and several dipoles concentrated along the rift axis for at least 250 km. The lineament analysis indicates widespread of the Erythrean (Red Sea) trend that was offset/cut by transform faults in the NE direction (Aqaba). The tectonic model suggests the presence of one tensional (N65°E) and two compressional (N15°W, N30°W) phases of tectonism, resulted in six cycles of deformations, classified into three left lateral (N35°E, N15°E and N–S) and three right lateral (N85°W, N45°W and N60°W). The basement relief map reveals a rough basement surface that varies in depth between 1 and 5.6 km. It outlines several offshore basins, separated from each other by ridges. The models show that the basement consists of tilted fault blocks, which vary greatly in depth and composition and slopes generally to the west. They indicate that the coastal plain is underlain by acidic basement blocks (continental crust) with no igneous activity while suggesting elevated basic materials (oceanic crust) below the rift axis. The study suggests that northern Red Sea forms an early stage of seafloor spreading or at least moved past the late stage of continental rifting.     

Wavelet transform-based seismic facies classification and modelling: application to a geothermal target horizon in the NE German Basin

At the geothermal test site near Groß Schönebeck (NE German Basin), a new 3D seismic reflection survey was conducted to study geothermal target layers at around 4 km depth and 150°C. We present a workflow for seismic facies classification and modelling which is applied to a prospective sandstone horizon within the Rotliegend formation. Signal attributes are calculated along the horizon using the continuous Morlet wavelet transform. We use a short mother wavelet to allow for the temporal resolution of the relatively short reflection signals to be analysed. Time-frequency domain data patterns form the input of a neural network clustering using self-organizing maps. Neural model patterns are adopted during iterative learning to simulate the information inherent in the input data. After training we determine a gradient function across the self-organizing maps and apply an image processing technique called watershed segmentation. The result is a pattern clustering based on similarities in wavelet transform characteristics. Three different types of wavelet transform patterns were found for the sandstone horizon. We apply seismic waveform modelling to improve the understanding of the classification results. The modelling tests indicate that thickness variations have a much stronger influence on the wavelet transform response of the sandstone horizon compared with reasonable variations of seismic attenuation. In our interpretation, the assumed thickness variations could be a result of variable paleo-topography during deposition of predominantly fluvial sediments. A distinct seismic facies distribution is interpreted as a system of thicker paleo-channels deposited within a deepened landscape. The results provide constraints for the ongoing development of the geothermal test site.     

High-resolution seismic imaging of crooked two-dimensional profiles in greenstone belts of the Canadian shield: results from the Swayze area,Ontario, Canada

In 2017, the Metal Earth multi-disciplinary exploration project acquired a total of 921 km of regional deep seismic reflection profiles and 184 km of high-resolution seismic reflection profiles in the Abitibi and Wabigoon greenstone belts of the Superior province of Canada. The Abitibi belt hosts several world-class mineral deposits, whereas the Wabigoon has sparse economic mineral deposits. Two high-resolution surveys in the Swayze area, a poorly endowed part of the western Abitibi greenstone belt, served as pioneer surveys with which to better understand subsurface geology and design a strategy to process other surveys in the near future. Swayze seismic data were acquired with crooked survey geometries along roads. Designing an effective seismic processing flow to address these geometries and complex geology required straight common midpoint lines along which both two-dimensional prestack dip-moveout correction and poststack migration processing were applied. The resulting seismic sections revealed steeply dipping and subhorizontal reflections; some correlate with folded surface rocks. An interpreted fault/deformation zone imaged in Swayze north would be a target for metal endowment if it extends the Porcupine–Destor structure. Because of the crooked line geometry of the surveys, two-dimensional /three-dimensional prestack time migration and swath three-dimensional processing were tested. The prestack time migration algorithm confirmed reflections at the interpreted base of the Abitibi greenstone belt. The swath three-dimensional images provided additional spatial details about the geometries of some reflections, but also had less resolution and did not detect many reflectors observed in two dimensions. Geological contacts between felsic, mafic and ultramafic greenstone rock layers are thought the main cause of reflectivity in the Swayze area.     

用Euler反褶积方法反演台湾海峡磁异常

用Ｅｕｌｅｒ反褶积方法反演台湾海峡磁异常,选取的窗口不能大,而决定取舍反褶积解的误差限又不能小,这势必对解的质量有较大影响．为此,不仅用了不同延深的单体模型,而且进行了多体模型实验．结果表明,复杂分布的磁性体,用Ｅｕｌｅｒ反褶积方法确定磁性体的轮廓可能是困难的,但可确定磁性体的水平位置和深度,从而降低了对资料精度和计算参数选取的要求．在磁异常比较复杂的地区．     

黑山铜镍矿重磁电异常解释

通过钻孔与地面物性测定,查明含矿岩体和硅质板岩都具有较高的极化率和相对较低的电阻率,是引起电性异常的主要因素。利用重磁异常推断岩体的空间分布形态为一向下延伸长度大于走向长度的岩柱。由重磁异常圈定的岩体范围内电性异常为矿体引起,其外为岩性异常,这是区分矿与非矿异常排除干扰的最佳标志。     

一种地下瞬变电磁法场值曲线的解释方法

均匀大地表面上大回线源在地下形成的瞬变电磁场解析计算式很复杂,无法用常规方法定义其视电阻率,而场值曲线本身分辨率低,进行分层解释困难。对大回线源在地下形成的瞬变电磁场场值,用由第一层介质充满半无限大地时的场值进行归一化的方法进行解释,经理论计算表明,与地面装置条件下的电阻率曲线进行解释有异曲同工之妙