【作者】 赵铁虎；

【导师】 王修田； 张训华；

【作者基本信息】 中国海洋大学 ， 海洋地球物理学， 2011， 博士

【摘要】 高分辨率声学探测技术是浅海松散沉积地层及其赋存资源调查的重要手段。尽管声学探测具有高效率、高分辨率的特点,但其目前尚存在着数据采集方法试验研究不足,缺少有效的去噪、速度分析和偏移归位成像处理等关键技术,这往往会严重影响到声地层剖面的质量,甚至会导致错误的地质解释。本文围绕声地层剖面技术进行了浅海声波传播特性和各种干扰波的成因机制的综合分析研究,探索了压制和消除干扰的数据采集方法,形成了适宜用于声地层剖面数据处理的组合去噪、反褶积处理、偏移成像以及道积分处理等关键技术,并应用于近海海砂资源调查和海底油气渗漏探测中。(1)在对声地层剖面探测中存在的干扰因素和自然条件影响进行系统分析的基础上,提出了对所用船只及航行因素、设备操作与换能器安装条件等关键环节应采取的针对性措施。(2)针对浅海环境下原始资料中存在直达波、折射波、多次波、低频随机噪声等干扰以及高频能量吸收严重、横向能量不均、振幅一致性差等问题,采用组合去噪和主能量脉冲反褶积处理技术,在保持脉冲反褶积相位特性的同时,主要在有效频带范围内拓宽频谱,从而保证了提高声地层分辨率的可靠性。(3)根据实测声地层剖面资料特点,通过分析与集成MBP地震资料处理软件系统的相关模块,采用克希霍夫积分偏移成像速度扫描的方法来获得声地层偏移速度,进而基于该优化选取的速度场进行偏移归位成像处理。这或许是第一次获得了声地层剖面的偏移归位成像。(4)采用不依赖测井资料的道积分处理,得到的相对波阻抗剖面较真实地反映了松散沉积物的物性变化,更易于目标地质体与较大套层的对比解释,有利于声地层层序的划分和地震相单元的分析。(5)将海底高分辨率声学探测与处理技术应用于我国珠江口近海海砂资源调查中,综合实测地形地貌特征、海底表层沉积物类型和区域地貌资料,按照形态-成因的分类原则,将研究区海底划分为三级地貌类型。一级地貌属南海北部内陆架；二级地貌由近现代海积平原和近现代残留混合堆积平原组成。其中,在近现代海积平原单元内发育有浅槽、侵蚀沟群、沙波、沙丘、古沙堤、凹凸地、陡坎、洼地等三级地貌,在近现代-残留混合堆积平原单元内发育有浅滩、陆架槽谷、沙脊、埋藏古河道、埋藏贝壳沙体等三级地貌；将研究区底质划分为砾砂(SG)、中粗砂(MCS)、细砂(FS)、粘土质粉砂(YT)和粉砂质粘土(TY)等5种类型；将探测深度范围以内的层序地层自上而下划分为冰消期海侵半旋回(层序Ⅰ)、末次冰期中晚期海进-海退旋回(层序Ⅱ)和层末次冰期早期海退半旋回(层序Ⅲ)；并划分出9个声反射界面(含亚界面)和8个地震相单元(含亚单元)；揭示了在珠江口近海存在4种成因类型的海砂矿,其分别为古残留砂类型、古潮流砂脊类型、古河道类型(或古潮沟类型)及现代潮流砂脊类型；指出了砂矿调查的主要方向：由于残留砂型砂矿直接出露海底,并具有分布范围广海砂品位较佳等特征,应为本区找矿的主要类型。(6)海底声学探测结果首次揭示了南黄海盆地北部坳陷选定区块海底油气渗漏现象的存在。渗漏形成的地貌以麻坑、海底圆丘和海底断裂(陡坎)为主,麻坑群大致呈SN向散布；发现了两处海底圆丘,其中,大圆丘的直径约1600m,最大凸起高度约6m；指出了该区海底油气渗漏与穿透或接近海底的断层构造相联系,这些断层为海底油气渗漏提供了通道和气源；通过对海底油气渗漏形成机理及其表征进行分析,推断该区海底油气目前处于微渗漏阶段,这可对该区未来的油气勘探提供重要的参考资料。更多还原

【Abstract】 Submarine high-resolution acoustic detection technique is an important method to investigate the sedimentary strata and resources in the offshore area. It is well-known that the acoustic detection has characteristics of high efficiency and high resolution. However, besides of the inadequate experimental investigations for data acquisition, it still suffers the problems lacking in key processing techniques such as effective noise elimination, velocity analysis and migration. This may seriously affect the quality of sub-bottom profile (SBP), and even lead to wrong geological interpretations.Focusing on the sub-bottom profile, this thesis makes a comprehensive analysis of shallow water acoustic wave propagation characteristics, the producing mechanism of various kinds of noises and their abatement approaches in acquisition. The key techniques of combined noise attenuation, deconvolution, migration imaging and trace integration are integrated to be suitable for SBP data processing. These techniques are then applied in the detections of sea sands and submarine hydrocarbon seepages.(1) Based upon the systematical analysis of noise and affection of natural conditions to data acquisition in sub-bottom profile detections, the specific measures are proposed for some key aspects such as survey vessels, navigation, equipment operation and the conditions of transducer installation.(2) There usually exist the direct waves, refractions, multiples and low frequency noise on the shallow water sub-bottom profile. Besides, the high frequency absorption, uneven horizontal energy and poor amplitude consistency are usually occurred in the raw data. These problems may be well overcome by using the combined noise attenuation techniques and the main energy impulse deconvolution approach. The processing is aimed at ensuring the reliability of SBP resolution by expanding the spectrum in the effective frequency range and keeping the phase characteristics of impulse deconvolution at the same time.(3) Based upon the analysis to the features of raw SBP data, the corresponding modules of MBP seismic software package are integrated to form a processing flow which is suitable for SBP data processing. The migration velocity can be obtained by the image scanning of Kirchhoff integration migration. Thus the SBP migration imaging can be made using the optimum velocity field. This may be the first time obtaining the migrated image in the sub-bottom profile detection.(4) The trace integrating technique which is independent on logging data is applied in the data processing. This relative impedance profiles processed by trace integrating may be in more reality to reveal the physical property of sedimentary formations. These profiles make not only the comparison and interpretation relatively easier to the geological features of targets and larger strata units, but also more reliable for the division of the stratigraphic sequence and analysis of seismic facies units.(5) The submarine high-resolution acoustic detection and processing techniques are then applied to marine sand investigation in the Pearl River Estuary offshore. Based on the topographical feature and sedimentary types of surface layer, the seafloor in the study area can be divided into 3 zonations of different topographic level according to morphological and genetic classification principle. The inner shelf of northern South China Sea belongs to the first level topography. The second-level topography includes modern marine accumulation plains and modern-residue mixed accumulation of plains. In the modern marine accumulation plain there develops the third-level landform such as shallow groove, erosion gully group, sand waves and dunes, ancient dike, convex, the scarp and depression, and in the modern-residue mixed accumulation of plains there develops shoals, shelf trough, and ridges, buried channels and buried shells. The bottom sediment in the study area can be classified into 5 types, i.e. gravel substrate sand (SG), medium-coarse sand (MCS), fine sand (FS), clayey silt (YT) and silty clay (TY). From seabed surface down to the detectable depth, the sequence stratigraphy can be divided into transgressive half cycle of deglaciation (sequence I), transgressive-regressive cycle of the middle-late glaciation (sequence II) and regressive half cycle of the early glaciation (sequence III). The shallow strata are divided into 9 interfaces of acoustic reflection (including sub-interfaces) and 8 units of seismic facies (including sub-units). The study reveals that there exist 4 genetic types of sea sand deposits in the Pearl River Estuary offshore area, which are the sands of ancient residual sand, sands of ancient tide ridge, sands of the ancient channel sand (or ancient tidal creek type) and sands of modern tide ridge sand. It is found that the ancient residual sand is directly exposed on seabed, widely distributed and has high-grade quality. Therefore it should be the main deposit for the sand exploration in study area.(6) It may be the first time that submarine acoustic detection results reveal the presence of submarine hydrocarbon seepage in selected block of the northern depression in the South Yellow Sea Basin. The landforms formed by seepages are predominant in pockmarks, domes and faults (scarp). The pockmarks are roughly spread in SN. Two domes on seabed are found. The bigger one is about 1600m in diameter and about 6m high. The study shows that submarine seepages in the area are associated with the faults penetrating or closing to the seabed. It is the faults that provide channels and sources of seepages. It can be deduced that, from analysis of the formation mechanism and characterization, the hydrocarbon seepage in study area is currently in micro-seepage stage.更多还原