中国海相油气田勘探实例之五塔中奥陶系大型凝析气田的勘探和发现

塔中奥陶系碳酸盐岩的勘探始于1989年,直至2005年发现塔中Ⅰ号坡折带奥陶系碳酸盐岩凝析气田,探明加控制石油地质储量1.5×108t(油当量),是我国目前发现的第一个奥陶系生物礁型大油气田。油气的主力产层位于上奥陶统良里塔格组上部,储层为受坡折带控制的陆棚边缘礁滩体石灰岩。油气沿坡折带呈带状展布,为整体含油的大型准层状岩性油气藏。论述了塔中碳酸盐岩大油气田的勘探历程、主要地质特征,以及对海相碳酸盐岩勘探的启示。     

基于Landsat-8遥感影像和LiDAR测深数据的水深主被动遥

主被动遥感结合反演远海岛礁周边水深信息,不仅可以有效弥补传统测深方法覆盖范围小且费时费力的不足,也可为航运安全、海洋减灾、生态环境保护等领域提供基础资料。以夏威夷瓦胡岛周边水深反演为例,应用Landsat-8多光谱遥感数据和机载Li DAR测深数据,开展了不同密度Li DAR测深数据对水深多光谱遥感反演精度的影响分析、不同水深网格化处理方法对水深遥感反演结果的影响分析和基于少量Li DAR控制区块的大区域水深反演能力分析三方面的研究工作。结果表明:(1)Li DAR测深数据密度的改变对水深反演结果的影响不大,变化后的水深反演结果与原始的水深反演结果相比,平均相对误差变化在0.3%以内,平均绝对误差变化在0.03m以内;(2)采用均值格网处理方法的多光谱遥感水深反演精度要略高于采用中值格网处理方法的水深反演精度,具体体现在均值的平均绝对误差要比中值的低0.04~0.05 m,平均相对误差低1%~10%,反演结果的残差分布显示在0~2 m和20~25 m的水深段内均值统计法的残差分布更集中且其平均值接近于0 m,而在其它水深段二者的残差分布基本相同;(3)基于少量Li DAR控制区块的大区域遥感水深反演结果较为理想,两个检查区块的水深反演结果 R2、平均绝对误差和平均相对误差分别为:0.877,1.66 m,3.5%和0.941,1.62 m,28.4%。反演结果分段分析表明各水深段内反演的精度都比较理想,平均绝对误差除20~25 m水深段外,均低于2.5 m,平均相对误差除0~2 m,2~5 m外,均低于25%。     

Remote sensing of water depths in shallow waters via artificial neural networks

Determination of the water depths in coastal zones is a common requirement for the majority of coastal engineering and coastal science applications. However, production of high quality bathymetric maps requires expensive field survey, high technology equipment and expert personnel. Remotely sensed images can be conveniently used to reduce the cost and labor needed for bathymetric measurements and to overcome the difficulties in spatial and temporal depth provision. An Artificial Neural Network (ANN) methodology is introduced in this study to derive bathymetric maps in shallow waters via remote sensing images and sample depth measurements. This methodology provides fast and practical solution for depth estimation in shallow waters, coupling temporal and spatial capabilities of remote sensing imagery with modeling flexibility of ANN. Its main advantage in practice is that it enables to directly use image reflectance values in depth estimations, without refining depth-caused scatterings from other environmental factors (e.g. bottom material and vegetation). Its function-free structure allows evaluating nonlinear relationships between multi-band images and in-situ depth measurements, therefore leads more reliable depth estimations than classical regressive approaches. The west coast of the Foca, Izmir/Turkey was used as a test bed. Aster first three band images and Quickbird pan-sharpened images were used to derive ANN based bathymetric maps of this study area. In-situ depth measurements were supplied from the General Command of Mapping, Turkey (HGK). Two models were set, one for Aster and one for Quickbird image inputs. Bathymetric maps relying solely on in-situ depth measurements were used to evaluate resultant derived bathymetric maps. The efficiency of the methodology was discussed at the end of the paper. It is concluded that the proposed methodology could decrease spatial and repetitive depth measurement requirements in bathymetric mapping especially for preliminary engineering application.     

基于可见光遥感测深技术的长江口南支河段河势演变规律研究

以长江口南支河段为研究区,利用LandsatETM+遥感影像反演的1999年水下地形和该河段2002年实测水深数据,结合长江口来水来沙现状和河段特征,分析了河段的冲淤变化和沙体迁移规律,提出了需采取的治理措施。研究结果表明:(1)从1999到2002年南支河段总体发生冲刷,年平均冲刷量为0.1926亿m3,河道内白茆沙、新浏河沙和新浏河沙包的沙头年平均后退467,374和421m;(2)上、下扁担沙之间由于串沟发育,两者有分离的趋势,沙体5m等深线的变动格局显示两沙体沙尾向下移动导致新桥水道上段水深加深、下段南侧水深变浅;(3)固定白茆沙和上、下扁担沙沙体,对维持南支河段航道的航运、稳定南北槽河势具有重要作用。     

Automatic Registration of TOBI Side-Scan Sonar and Multi-Beam Bathymetry Images for Improved Data Fusion

Deep towed side-scan sonar vehicles such as TOBI acquire high quality imagery of the seafloor with very high spatial resolution but poor locational accuracy. Fusion of the side-scan sonar data with bathymetry data from an independent source is often desirable to reduce ambiguity in geological interpretations, to aid in slant-range correction and to enhance seafloor representation. The main obstacle to fusion is accurate registration of the two datasets.The application of hierarchical chamfer matching to the registration of TOBI side-scan sonar images and multi-beam swath bathymetry is described. This matches low level features such as edges in the TOBI image, with corresponding features in a synthetic TOBI image created by simulating the flight of the TOBI vehicle through the bathymetry. The method is completely automatic, relatively fast and robust, and much easier than manual registration. It allows accurate positioning of the TOBI vehicle, enhancing its usefulness as a research tool. The method is illustrated by automatic registration of TOBI and multi-beam bathymetry data from the Mid-Atlantic Ridge.     

Feature based image processing methods applied to bathymetric measurements from airborne remote sensing in fluvial environments

Bathymetric maps produced from remotely sensed imagery are increasingly common. However, when this method is applied to fluvial environments, changing scenes and illumination variations severely hinder the application of well established empirical calibration methods used to obtain predictive depth–colour relationships. In this paper, illumination variations are corrected with feature based image processing, which is used to identify areas in an image with a near‐zero water depth. This information can then be included in the depth–colour calibration process, which results in an improved prediction quality. The end product is an automated bathymetric mapping method capable of a 4 m² spatial resolution with a precision of ±15 cm, which allows for a more widespread application of bathymetric mapping. Copyright © 2006 John Wiley & Sons, Ltd.     

机载激光测深系统强度数据AGC补偿异常区域识别及改正

机载激光测深系统（Airborne Laser Bathymetry,ALB）因集成了具有独特水体穿透能力的绿波段（532 nm）而被广泛用于水深测量。除地形数据外,ALB还记录了地物目标的辐射特性（后向散射强度）,可用于条带配准、海底底质分类和几何建模。然而,由于自动增益控制（Automatic Gain Control,AGC）设计局限,增益值调整存在延缓,对于裸露岩石、水域等高返回、低返回目标较多的海岛海岸带区域,强度补偿异常问题格外突出。针对该问题本文设计了一种基于双向移动的局部加权强度改正方法,提出索引共享机制辅以地形信息实现有效强度数据精确提取;以扫描周期为依据进行扫描线分割,通过柯尔莫可洛夫−斯米洛夫检验进行强度补偿异常区识别;通过对邻近扫描线和邻域强度联合加权进行强度改正,保证强度细节的同时较好地消除与邻域强度偏差,独特的双向移动策略能有效削弱改正不足积累造成的强度改正精度下降问题。实验证明该方法能有效解决AGC补偿异常问题,相较于改正前,改正后的强度数据平均绝对百分比误差降低了约0.27,均方根误差下降了约693,异常区强度与邻域强度偏差控制在26 DN（Digital Number）以内,得到高质量强度图像。     

Long-term changes in coral assemblages under natural and anthropogenic stress in Jakarta Bay (1920-2005)

Coral reefs in Jakarta Bay have been subjected to scientific studies since the 1920s. Also from that time on biological collections were made. The reefs in the Jakarta Bay have been under long-term natural and anthropogenic stress. With the biological collections and historical documents the coral species richness in Jakarta Bay around 1920 was reconstructed. New data from this bay and the adjacent offshore Thousand Islands archipelago were obtained during a 2005 research expedition. A comparison of the coral assemblages between 1920 and 2005 reveals a clear decline in species numbers. The most prominent results include the near-shore disappearance of species belonging to the families Acroporidae, Milleporidae, and to a lesser extent Poritidae. The overall coral species composition of the reefs has changed considerably, which is partly reflected in a strong decline in coral species richness. About half the number of species recorded in 1920 was found again in 2005.     

Estimation of size at first maturity in two South African coral species

The corals Acropora austera and Platygyra daedalea have been the subject of extensive reproductive and population genetic studies in the iSimangaliso Wetland Park (iSimangaliso), on the KwaZulu-Natal coast, eastern South Africa. Despite this, estimates of size at first maturity in these two species are lacking. This information could be used to provide a baseline to differentiate juveniles from adult sizes of corals, an important factor for assessing the condition of scleractinian communities in reefs. Here, we present the methods followed to provide such estimates for these two hard corals. Using generalised linear models and assuming knife-edge maturity (50% probability), it was estimated that A. austera from iSimangaliso matures at c. 15 cm mean colony diameter (MCD) (95% CI: 9.25–20.75 cm MCD) and P. daedalea matures at c. 7 cm MCD (95% CI: 4.55–8.39 cm MCD). These estimates were comparable to those for tropical species which is remarkable considering the high-latitude nature of the sampled reefs. It is expected that the findings from this study will assist in the assessment of reproduction, recruitment, survival and genetic variation in clonal organisms such as corals, and will provide a baseline to assess the effects of climate change on coral communities in the region.