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Submarine High-resolution Acoustic Detection and the Application

作　者: 赵铁虎
导　师: Wang Xiutian；Zhang Xunhua
学　校: 中国海洋大学
专　业: 海洋地球物理学
关键词: submarine acoustic detection SBP processing sea sand resources submarine hydrocarbon seepage
分类号: P714
类　型: 博士论文
年　份: 2011年
下　载: 12次
引　用: 0次
阅　读: 论文下载

内容摘要

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 (sequenceⅠ), transgressive-regressive cycle of the middle-late glaciation (sequenceⅡ) and regressive half cycle of the early glaciation (sequenceⅢ). 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.

全文目录

Abstract  5-12
1 Introduction  12-37
  1.1 The purpose and significance of the research  12-14
  1.2 The research status and problems in domestic and international  14-30
    1.2.1 Overview of submarine acoustic detection technology  14-17
    1.2.2 Overview of submarine hydrocarbon seepages and sea sands detection  17-29
    1.2.3 The main problems of existence  29-30
  1.3 The research ideas and contents  30-33
    1.3.1 The research ideas  30-31
    1.3.2 The main contents  31-33
  1.4 The main research results and innovations  33-37
    1.4.1 The main research results  33-34
    1.4.2 The main innovations  34-37
2 Theory of submarine high-resolution acoustic detection  37-54
  2.1 Principle of submarine high-resolution acoustic detection  37-42
    2.1.1 Reflection and transmission of submarine acoustic waves  37-39
    2.1.2 Reflection loss of submarine acoustic propagation  39-41
    2.1.3 Submarine acoustic scattering  41-42
  2.2 Sonar detection equation  42-43
  2.3 Submarine high-resolution acoustic detection system  43-48
    2.3.1 The transmitter units  44-45
    2.3.2 The receiver units  45-46
    2.3.3 The auxiliary units  46
    2.3.4 Key performance indicators  46-48
  2.4 Acoustic field characters of SBP  48-54
    2.4.1 Signal-to-noise ratio  48-52
    2.4.2 Echo-to-reverberation ratio  52-54
3 Key technologies of submarine high-resolution acoustic detection  54-95
  3.1 Data acquisition  54-59
    3.1.1 General description  54-55
    3.1.2 Acoustic source selections  55-57
    3.1.3 Receiver hydrophone  57-58
    3.1.4 Analysis of seismic geology conditions  58-59
  3.2 Interference factors and suppressions  59-82
    3.2.1 Noise analysis  59-61
    3.2.2 Multiple reflections and its suppressions  61-63
    3.2.3 The interferences caused by the directional properties of acoustic arrays and its suppressions  63-68
    3.2.4 Ringing interference of emitting transducer and its suppression  68
    3.2.5 Other interferences and their suppression  68-69
    3.2.6 Methods test of SBP  69-82
  3.3 The processing of SBP data  82-93
    3.3.1 Combined denoising and deconvolution processing  83-85
    3.3.2 Offset processing  85-88
    3.3.3 Trace integral processing  88-93
  3.4 Chapter summary  93-95
4 Application of sea sand resources survey in the Pearl River estuary offshore  95-154
  4.1 Regional geological setting  95-121
    4.1.1 Natural geographical situations  95-96
    4.1.2 Geological tectonic overview  96-97
    4.1.3 Seabed topography  97-106
    4.1.4 Submarine sediment types  106-111
    4.1.5 Sedimentary characteristics of Late Quaternary  111-121
  4.2 Sequence stratigraphic subdivision  121-123
    4.2.1 Transgression half-cycle of deglaciation  121-122
    4.2.2 Transgression-regression cycles of the mid to late period in the last glacial  122
    4.2.3 Regression half-cycle in the early last glacial  122-123
  4.3 Analysis of seismic facies units  123-145
    4.3.1 Reflecting interface tracking and stratigraphic division  123-130
    4.3.2 Sedimentary explanations of seismic facies units  130-137
    4.3.3 Acoustic features of sandy geological bodies  137-145
  4.4 Identification of sea sands  145-151
    4.4.1 Types and distributions of sea sands  145-146
    4.4.2 Deposits geological characteristics  146
    4.4.3 Deposits spatial distribution  146-147
    4.4.4 Variation characteristics of sands grade  147-148
    4.4.5 Deposit genesis and prospecting way  148-151
  4.5 Chapter summary  151-154
5 Application of submarine hydrocarbon seepage detection in the Southern Yellow Sea  154-174
  5.1 The situation of the study area  154-155
    5.1.1 The location  154
    5.1.2 Submarine topography  154-155
  5.2 Petroleum geology conditions  155-161
    5.2.1 Tectonic setting  155-156
    5.2.2 Hydrocarbon bearing zone  156-158
    5.2.3 Hydrocarbon traps  158-161
  5.3 Characteristics and analysis of seabed hydrocarbon seepages  161-172
    5.3.1 Acoustic geomorphology responses  161-168
    5.4.2 Acoustic reflection features  168-172
  5.4 Chapter summary  172-174
6 Conclusions and suggestions  174-180
  6.1 Conclusions  174-178
  6.2 Suggestions  178-180
References  180-190
Acknowledgements  190-191
Personal Particulars  191-192
Published Papers  192

Submarine High-resolution Acoustic Detection and the Application

内容摘要

全文目录

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